Article Type
Article
Changed
Wed, 11/06/2019 - 09:40
Author(s)
Nathan Merritt Johnson, MD
Kyle A. Prickett, MD
Mariana A. Phillips, MD

Dermatologists are increasingly called on to evaluate patients with complex medical problems who are often taking many medications. Over the last several decades, many new drugs that target molecular pathways in carcinogenesis and the inflammatory immune system have been developed. Increased skin cancer risk has been reported in association with BRAF inhibitors, sonic hedgehog–inhibiting agents, Janus kinase (JAK) inhibitors, and phosphodiesterase 5 (PDE-5) inhibitors. We review the literature and data regarding the significance and strength of these associations and the molecular pathways by which these medications promote cutaneous tumorigenesis. The association of skin cancer with drugs that either induce photosensitivity—nonsteroidal anti-inflammatory drugs, antibiotics (eg, tetracyclines, fluoroquinolones, trimethoprim-sulfamethoxazole), voriconazole, thiazides—or suppress the immune system—certain biologics (eg, anti–tumor necrosis factor agents), calcineurin inhibitors, thiopurines, methotrexate, cyclosporine—is well known and is therefore not reviewed in this discussion.

BRAF Inhibitors

The mitogen-activated protein kinase (MAPK) pathway (also known as the RAS/RAF/MAPK signaling pathway) is important in growth factor–receptor signaling and plays a key role in cell differentiation, survival, and proliferation. Activating mutations in this pathway allow cells to grow and proliferate in a growth factor–independent manner. Twenty percent of human cancers harbor a mutation in the RAS oncogene, an upstream mediator of the pathway.1 Activating mutations in BRAF, a serine/threonine kinase, predominate in cutaneous melanoma and also have been found in 40% to 70% of papillary thyroid malignancies, 10% to 20% of cholangiocarcinomas, and 5% to 20% of colorectal carcinomas. The most common BRAF mutation in cutaneous melanoma is V600E, which involves a glutamic acid for valine substitution at codon 600. This mutation activates BRAF 500-fold and is present in approximately 50% of melanomas.1,2

Vemurafenib, a selective BRAF inhibitor, was approved by the US Food and Drug Administration (FDA) for the treatment of metastatic melanoma in the United States in 2011. Phase 3 trial data demonstrated that vemurafenib resulted in improved survival and decreased risk for disease progression compared to dacarbazine, the former best treatment.3 During phase 1 testing, it became apparent that vemurafenib treatment was associated with a 31% increased risk for squamous cell carcinoma (SCC), most commonly well-differentiated SCC, and keratoacanthomas (KAs).4 This association was confirmed in phase 2 and 3 studies, though the incidence was lower. McArthur et al5 reported a 19% incidence of cutaneous SCC with extended follow-up analysis of the phase 3 trial. Dabrafenib, another BRAF inhibitor, has been similarly associated with increasing the risk for SCC and KA.

In one study, the mean time to development of SCC after initiating vemurafenib therapy was 10 weeks, with lesions reported as early as 3 weeks. Most patients had clinical signs of chronically sun damaged skin; however, a history of SCC was present in only 17%. Most lesions (63%) were characterized as KAs.6

The mechanism for BRAF inhibitor–induced squamoproliferative growth is due to paradoxical activation of the MAPK pathway in cells with wild-type BRAF that harbor upstream-activating mutations in RAS or tyrosine kinase receptors.7 In the presence of a BRAF inhibitor, inactivated BRAF forms heterodimers with wild-type CRAF (a BRAF-CRAF heterodimer). The heterodimer forms a complex with the mutant RAS that leads to transactivation of the CRAF molecule,8,9 resulting in a paradoxical increase in MAPK signaling and consequent ERK phosphorylation and activation through CRAF signaling. RAS, particularly HRAS, mutations have been found in 60% of all vemurafenib-associated SCCs and KAs. For this reason, it is thought that vemurafenib potentiates tumorigenesis in subclinical lesions harboring upstream MAPK pathway mutations as opposed to inducing de novo lesions.6

Because BRAF inhibitors are remarkably efficacious in the treatment of metastatic melanomas harboring the V600E BRAF mutation, there are no restrictions on their use, despite the known increased risk for SCC. Squamous cell carcinomas tend to be low grade, and all tumors that developed in phase 1 to 3 trials were treated with simple excision. The development of SCC did not necessitate interruption of treatment. Furthermore, the addition of MEK inhibition to BRAF inhibitor therapy reduces the risk for SCC from 19% to 7%.7,10,11

In addition to SCC, second primary melanomas (SPMs) have been reported in patients treated with BRAF inhibitors. It has been shown that these melanomas occur in melanocytes with wild-type BRAF. It has been postulated that some of these tumors occur in cells that harbor upstream mutations in RAS, whereas others might result from alternate signaling through non-RAF oncogenic pathways.9,12



Zimmer et al1 reported 12 SPMs in 11 patients treated with BRAF inhibitor therapy. They reported a median delay of 8 weeks (range, 4–27 weeks) for SPM development. Tumors were detected in early stages; 1 tumor harbored an NRAS mutation.1

 

 


Dalle et al13 reported 25 SPMs in 120 vemurafenib-treated patients. Median delay in SPM development was 14 weeks (range, 4–42 weeks). All tumors were thin, ranging from in situ to 0.45-mm thick. Wild-type BRAF was detected in the 21 melanomas sampled; 1 lesion showed mutated NRAS.13



The exact incidence of SPM in the setting of BRAF inhibition is thought to be at least 10-fold less than SCC and KA.2 Patients on BRAF inhibitor therapy should have routine full-body skin examinations, given the increased risk for SPM and SCC.

Another drug belonging to the tyrosine kinase inhibitor family, sorafenib, is used in the treatment of solid tumors, particularly hepatocellular and renal cell carcinomas, and also has been associated with development of cutaneous SCC and KAs.14 Sorafenib is a multiple tyrosine kinase inhibitor that also inhibits the RAF serine/threonine kinases. Similar to vemurafenib and dabrafenib, SCCs and KAs associated with sorafenib tend to arise in patients with chronic actinic damage during the first 2 months of treatment. It has been hypothesized that inhibition of RAF kinases is pathogenic in inducing SCCs because these lesions have not been reported with sunitinib, another multiple tyrosine kinase inhibitor that lacks the ability to inhibit serine/threonine kinases.15,16 Although SCCs and KAs associated with sorafenib tend to be low grade, it is reasonable to consider sunitinib or an alternative tyrosine kinase inhibitor in patients who develop multiple SCCs while taking sorafenib.16

Sonic Hedgehog–Inhibiting Agents

Vismodegib, the first small molecule inhibitor of the signaling protein smoothened, gained FDA approval for the treatment of metastatic or locally advanced basal cell carcinoma (BCC) in 2012. A second agent with an identical mechanism of action, sonidegib, was approved by the FDA for locally advanced BCC in 2015. Approximately 90% of BCCs contain mutations in the sonic hedgehog pathway, which lead to constitutive smoothened activation and uncontrolled cell proliferation.17 The development of smoothened inhibitors introduced a much-needed treatment for inoperable or metastatic BCC,17,18 though long-term utility is limited by drug resistance with extended use in this patient population.19,20 Several case reports have documented the emergence of KA21 and cutaneous SCC following vismodegib treatment of advanced or metastatic BCC.22-24 A larger case-control study by Mohan et al25 showed that patients with BCC treated with vismodegib had an increased risk for non-BCC malignancy (hazard ratio [HR]=6.37), most of which were cutaneous SCC (HR=8.12).

The mechanism by which selective inhibition of smoothened leads to cutaneous SCC is unclear. A study found that patients on vismodegib who developed SCC within the original BCC site had elevated ERK levels within tumor tissue, suggesting that the RAS/RAF/MAPK pathway can become upregulated during hedgehog inhibition.26 Other studies looking at hedgehog inhibition in medulloblastoma models also have shown activated RAS/RAF/MAPK pathways.25 These findings suggest that tumors under smoothened inhibition might be able to bypass the sonic hedgehog pathway and continue to grow by upregulating alternative growth pathways, such as RAS/RAF/MAPK.25,26

The incidence of cutaneous SCC following vismodegib treatment is unknown. Chang and Oro27 examined BCC tumor regrowth from secondary (acquired) resistance to vismodegib and noted that lesions recurred within 1 cm of the original tumor 21% of the time. Although none of the 12 patients whose tumors regrew during treatment were reported to have developed SCC, several demonstrated different BCC subtypes than the pretreatment specimen. The authors proposed that regrowth of BCC was due to upregulated alternative pathways allowing tumors to bypass smoothened inhibition, which is similar to the proposed mechanism for SCC development in vismodegib patients.27



Prospective studies are needed to confirm the link between vismodegib and cutaneous SCC; establish the incidence of SCC development; and identify any pretreatment factors, tumor characteristics, or treatment details (eg, dosage, duration) that might contribute to SCC development. Furthermore, because Mohan et al25 observed that vismodegib-treated patients were less likely to develop SCC in situ than controls, it is unknown if these tumors are more aggressive than traditional SCC. At this point, careful surveillance and regular full-body skin examinations are advised for patients on vismodegib for treatment of advanced BCC.

 

 

JAK Inhibitors

Another class of medications potentially associated with increased development of nonmelanoma skin cancer (NMSC) is the JAK inhibitors (also known as jakinibs). Many proinflammatory signaling pathways converge on the JAK family of enzymes—JAK1, JAK2, JAK3, and TYK2. These enzymes operate in cytokine signal transduction by phosphorylating activated cytokine receptors, which allows for recruitment and activation by means of phosphorylation of transcription factors collectively known as signal transducers and activators of transcription (STATs). Phosphorylated STATs dimerize and translocate to the nucleus, acting as direct transcription promoters. Janus kinase inhibitors modulate the immune response by reducing the effect of interleukin and interferon signaling.

Ruxolitinib, a JAK1/JAK2 inhibitor, was the first JAK inhibitor approved by the FDA and is indicated for the treatment of myelofibrosis and polycythemia vera. Additionally, oral and topical JAK inhibitors have shown efficacy in the treatment of psoriasis, rheumatoid arthritis, alopecia areata, vitiligo, and pruritus from atopic dermatitis.28

The JAK-STAT pathway is complex, and the biological activity of the pathway is both proinflammatory and pro–cell survival and proliferation. Because signaling through the pathway can increase angiogenesis and inhibit apoptosis, inhibition of this pathway has been exploited for the treatment of some tumors. However, inhibition of interferon and proinflammatory interleukin signaling also can potentially promote tumor growth by means of inhibition of downstream cytotoxic T-cell signaling, theoretically increasing the risk for NMSC. A study examining the 5-year efficacy of ruxolitinib in myelofibrosis patients (COMFORT-II trial) found that 17.1% of patients developed NMSC compared to only 2.7% of those on the best available therapy. After adjustment by patient exposure, the NMSC rate was still doubled for ruxolitinib-treated patients compared to controls (6.1/100 patient-years and 3.0/100 patient-years, respectively).29 Eighty-week follow-up of the phase 3 clinical trial of ruxolitinib for the treatment of polycythemia vera also noted an increased incidence of NMSC, albeit a more conservative increase. Patients randomized to the ruxolitinib treatment group developed NMSC at a rate of 4.4/100 patient-years, whereas the rate for controls treated with best available therapy was 2.7/100 patient-years.30 In contrast, 5-year follow-up of the COMFORT-I trial, also examining the efficacy of ruxolitinib in myelofibrosis, showed no increased risk for NMSC between ruxolitinib-treated patients and placebo (2.7/100 patient-years and 3.9/100 patient-years, respectively).31

A 2017 case series described 5 patients with myelofibrosis who developed multiple skin cancers with aggressive features while receiving ruxolitinib.32 Duration of ruxolitinib therapy ranged from 4 months to 4 years; 3 patients had a history of hydroxyurea exposure, and only 1 patient had a history of NMSC. High-risk cutaneous SCC, undifferentiated pleomorphic sarcoma, and lentigo maligna melanoma (Breslow thickness, 0.45 mm) were among the tumors reported in this series. Although no definitive conclusion can be made regarding the causality of JAK inhibitors in promoting these tumors, the association warrants further investigation. Clinicians should be aware that ruxolitinib might amplify the risk for NMSC in patients with pre-existing genetic or exposure-related susceptibility. Interruption of drug therapy may be necessary in managing patients who develop an aggressive tumor.32

In contrast, tofacitinib, which specifically inhibits JAK3, carries very low risk, if any, for NMSC when used for the treatment of psoriasis and rheumatoid arthritis. Results from 2 phase 3 trials analyzing the efficacy of tofacitinib in psoriasis demonstrated that only 2 of 1486 patients treated developed NMSC compared to none in the control group.33 Furthermore, analysis of NMSC across the tofacitinib rheumatoid arthritis clinical program, which included a total of 15,103 patient-years of exposure, demonstrated that the overall NMSC incidence was 0.55 for every 100 patient-years. Of note, the risk in patients receiving high-dose treatment (10 mg vs 5 mg) was nearly doubled in long-term follow-up studies (0.79/100 patient-years and 0.41/100 patient-years, respectively). Overall, the study concluded that treatment with tofacitinib presents no greater increased risk for NMSC than treatment with tumor necrosis factor inhibitors.33

PDE-5 Inhibitors

Phosphodiesterase 5 inhibitors, such as sildenafil citrate, have been widely prescribed for the treatment of erectile dysfunction. Studies have shown that BRAF-activated melanomas, which occur in approximately 50% to 70% of melanomas, also result in reduced PDE-5 expression.34-36 In these melanomas, downregulation of PDE-5 results in increased intracellular calcium,36 which has been shown to induce melanoma invasion.36,37 Given this similarity in molecular pathway between BRAF-activated melanomas and PDE-5 inhibitors, there has been increased concern that PDE-5 inhibitors might be associated with an increased risk for melanoma.

In 2014, Li et al38 published a retrospective analysis suggesting an association with sildenafil and an increased risk for melanoma. Their study utilized the Health Professionals Follow-up Study to identify a statistically significant elevation in the risk for invasive melanoma with both recent sildenafil use (multivariate-adjusted HR=2.24) and use at any time (HR=1.92). These results controlled for confounding variables, such as presence of major chronic disease, use of other erectile dysfunction treatments, family history of melanoma, history of sun exposure, and UV index of the patient’s residence. Notably, the study also found that sildenafil did not affect the incidence of BCC or SCC.38

 

 

In 2015, Loeb et al39 also examined the potential association between PDE-5 inhibitors and melanoma. Review of several Swedish drug and cancer registries allowed for analysis of melanoma risk and PDE-5 inhibitor use, based on number of prescriptions filled and type of PDE-5 inhibitor prescribed. Their analysis showed that men developing melanoma were more likely than nonmelanoma controls to have taken a PDE-5 inhibitor (11% vs 8%). In a subgroup analysis, however, statistical significance was shown for men with only a single prescription filled (34% of cases; P<.05), whereas the difference for men with multiple filled prescriptions did not meet statistical significance. Furthermore, the study did not find increased risk with longer-acting tadalafil and vardenafil (odds ratio [OR]=1.16) compared to sildenafil (OR=1.14). Last, use of PDE-5 inhibitors was only associated with stage 0 (OR=1.49) and stage I (OR=1.21) tumors, not with stages II to IV (OR=0.83) tumors. Although there was a statistically significant association between PDE-5 inhibitors and malignant melanoma (P<.05), the subgroup analysis findings pointed away from a causal relationship and likely toward a confounding of variable(s).39



A 2016 study by Lian et al40 looked at the risk for melanoma in a cohort of patients diagnosed with erectile dysfunction. No association between PDE-5 inhibitors and melanoma risk was shown when comparing patients who received a PDE-5 inhibitor and those who did not receive a PDE-5 inhibitor. However, secondary analysis did show that melanoma risk was increased among patients receiving more pills (34%) and prescriptions (30%). The authors concluded that there was no association between PDE-5 inhibitor use and overall increased risk for melanoma, and the increased risk associated with a greater number of pills and prescriptions would require further study.40

In contrast, a 2017 meta-analysis by Tang et al41 of 5 studies (3 of which were the aforementioned trials38-40) concluded that use of PDE-5 inhibitors was associated with a small but significantly increased risk for melanoma (OR=1.12) and BCC (OR=1.14) but not SCC. Furthermore, the study found no evidence of dosage-dependent association between PDE-5 inhibitor use and melanoma risk.41



Overall, clinical studies have been inconclusive in determining the risk for melanoma in the setting of PDE-5 inhibitor use. Studies showing an increased rate of melanoma within patient cohorts receiving PDE-5 inhibitors are limited; results might be affected by confounding variables. However, given the similarity in mechanism between PDE-5 inhibitors and HRAS-activated melanomas, it is reasonable to continue research into this potential association.

Conclusion

Since the turn of the century, drugs targeting cell-signaling pathways have been developed to treat inflammatory, oncologic, and immune conditions. The role of immunosuppressants in promoting skin cancer is well established and supported by a vast literature base. However, associations are less clear with newer immunomodulatory and antineoplastic medications. Skin cancer has been reported in association with BRAF inhibitors, sonic hedgehog–inhibiting agents, JAK inhibitors, and PDE-5 inhibitors. In the case of JAK and PDE-5 inhibitors, the increased risk for melanoma and NMSC is somewhat inconclusive; risk is more firmly established for BRAF inhibitors and smoothened inhibitors. For the antineoplastic agents reviewed, the therapeutic effect of cancer regression is well documented, and benefits of continued therapy outweigh the increased risk for skin cancer promotion in nearly all cases. The value of early detection has been well documented for skin malignancy; therefore, increased skin surveillance and prompt management of suspicious lesions should be a priority for physicians treating patients undergoing therapy with these medications

References
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  11. Robert C, Karaszewska B, Schachter J, et al. Improved overall survival in melanoma with combined dabrafenib and trametinib. N Engl J Med. 2015;372:30-39.
  12. Holderfield M, Nagel TE, Stuart DD. Mechanism and consequence of RAF kinase activation by small-molecule inhibitors. Br J Cancer. 2014;111:640-645.
  13. Dalle S, Poulalhon N, Debarbieux S, et al. Tracking of second primary melanomas in vemurafenib-treated patients. JAMA Dermatol. 2013;149:488-490.
  14. Williams VL, Cohen PR, Stewart DJ. Sorafenib-induced premalignant and malignant skin lesions. Int J Dermatol. 2011;50:396-402.
  15. Arnault JP, Wechsler J, Escudier B, et al. Keratoacanthomas and squamous cell carcinomas in patients receiving sorafenib. J Clin Oncol. 2009;27:e59-e61.
  16. Smith KJ, Haley H, Hamza S, et al. Eruptive keratoacanthoma-type squamous cell carcinomas in patients taking sorafenib for the treatment of solid tumors. Dermatol Surg. 2009;35:1766-1770.
  17. Sekulic A, Migden MR, Oro AE, et al. Efficacy and safety of vismodegib in advanced basal-cell carcinoma. N Engl J Med. 2012;366:2171-2179.
  18. Demirci H, Worden F, Nelson CC, et al. Efficacy of vismodegib (Erivedge) for basal cell carcinoma involving the orbit and periocular area. Ophthalmic Plast Reconstr Surg. 2015;31:463-466.
  19. Atwood SX, Sarin KY, Whitson RJ, et al. Smoothened variants explain the majority of drug resistance in basal cell carcinoma. Cancer Cell. 2015;27:342-353.
  20. Ridky TW, Cotsarelis G. Vismodegib resistance in basal cell carcinoma: not a smooth fit. Cancer Cell. 2015;27:315-316.
  21. Aasi S, Silkiss R, Tang JY, et al. New onset of keratoacanthomas after vismodegib treatment for locally advanced basal cell carcinomas: a report of 2 cases. JAMA Dermatol. 2013;149:242-243.
  22. Orouji A, Goerdt S, Utikal J, et al. Multiple highly and moderately differentiated squamous cell carcinomas of the skin during vismodegib treatment of inoperable basal cell carcinoma. Br J Dermatol. 2014;171:431-433.
  23. Iarrobino A, Messina JL, Kudchadkar R, et al. Emergence of a squamous cell carcinoma phenotype following treatment of metastatic basal cell carcinoma with vismodegib. J Am Acad Dermatol. 2013;69:e33-e34.
  24. Saintes C, Saint-Jean M, Brocard A, et al. Development of squamous cell carcinoma into basal cell carcinoma under treatment with vismodegib. J Eur Acad Dermatol Venereol. 2015;29:1006-1009.
  25. Mohan SV, Chang J, Li S, et al. Increased risk of cutaneous squamous cell carcinoma after vismodegib therapy for basal cell carcinoma. JAMA Dermatol. 2016;152:527-532.
  26. Zhao X, Ponomaryov T, Ornell KJ, et al. RAS/MAPK activation drives resistance to Smo inhibition, metastasis, and tumor evolution in Shh pathway-dependent tumors. Cancer Res. 2015;75:3623-3635.
  27. Chang AL, Oro AE. Initial assessment of tumor regrowth after vismodegib in advanced basal cell carcinoma. Arch Dermatol. 2012;148:1324-1325.
  28. Damsky W, King BA. JAK inhibitors in dermatology: the promise of a new drug class. J Am Acad Dermatol. 2017;76:736-744.
  29. Harrison CN, Vannucchi AM, Kiladjian JJ, et al. Long-term findings from COMFORT-II, a phase 3 study of ruxolitinib vs best available therapy for myelofibrosis. Leukemia. 2016;30:1701-1707.
  30. Verstovsek S, Vannucchi AM, Griesshammer M, et al. Ruxolitinib versus best available therapy in patients with polycythemia vera: 80-week follow-up from the RESPONSE trial. Haematologica. 2016;101:821-829.
  31. Verstovsek S, Mesa RA, Gotlib J, et al; COMFORT-I investigators. Long-term treatment with ruxolitinib for patients with myelofibrosis: 5-year update from the randomized, double-blind, placebo-controlled, phase 3 COMFORT-I trial. J Hematol Oncol. 2017;10:55.
  32. Blechman AB, Cabell CE, Weinberger CH, et al. Aggressive skin cancers occurring in patients treated with the Janus kinase inhibitor ruxolitinib. J Drugs Dermatol. 2017;16:508-511.
  33. Papp KA, Menter MA, Abe M, et al; OPT Pivotal 1 and OPT Pivotal 2 investigators. Tofacitinib, an oral Janus kinase inhibitor, for the treatment of chronic plaque psoriasis: results from two randomized, placebo-controlled, phase III trials. Br J Dermatol. 2015;173:949-961.
  34. Wellbrock C, Karasarides M, Marais R. The RAF proteins take centre stage. Nat Rev Mol Cell Biol. 2004;5:875-885.
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  37. Houslay MD. Hard times for oncogenic BRAF-expressing melanoma cells. Cancer Cell. 2011;19:3-4.
  38. Li WQ, Qureshi AA, Robinson KC, et al. Sildenafil use and increased risk of incident melanoma in US men: a prospective cohort study. JAMA Intern Med. 2014;174:964-970.
  39. Loeb S, Folkvaljon Y, Lambe M, et al. Use of phosphodiesterase type 5 inhibitors for erectile dysfunction and risk of malignant melanoma. JAMA. 2015;313:2449-2455.
  40. Lian Y, Yin H, Pollak MN, et al. Phosphodiesterase type 5 inhibitors and the risk of melanoma skin cancer. Eur Urol. 2016;70:808-815.
  41. Tang H, Wu W, Fu S, et al. Phosphodiesterase type 5 inhibitors and risk of melanoma: a meta-analysis. J Am Acad Dermatol. 2017;77:480.e9-488.e9.
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From Carilion Clinic Dermatology & Mohs Surgery and Virginia Tech Carilion School of Medicine, Roanoke.

The authors report no conflict of interest.

Correspondence: Nathan Merritt Johnson, MD, 1 Riverside Cir, Ste 300, Roanoke, VA 24016 (nmjohnson@carilionclinic.org).

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Cutis
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Melanoma
Nonmelanoma Skin Cancer
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Author(s)
Nathan Merritt Johnson, MD
Kyle A. Prickett, MD
Mariana A. Phillips, MD
Author(s)
Nathan Merritt Johnson, MD
Kyle A. Prickett, MD
Mariana A. Phillips, MD
Author and Disclosure Information

From Carilion Clinic Dermatology & Mohs Surgery and Virginia Tech Carilion School of Medicine, Roanoke.

The authors report no conflict of interest.

Correspondence: Nathan Merritt Johnson, MD, 1 Riverside Cir, Ste 300, Roanoke, VA 24016 (nmjohnson@carilionclinic.org).

Author and Disclosure Information

From Carilion Clinic Dermatology & Mohs Surgery and Virginia Tech Carilion School of Medicine, Roanoke.

The authors report no conflict of interest.

Correspondence: Nathan Merritt Johnson, MD, 1 Riverside Cir, Ste 300, Roanoke, VA 24016 (nmjohnson@carilionclinic.org).

Article PDF
CT104004032_e.PDF
Article PDF
CT104004032_e.PDF

Dermatologists are increasingly called on to evaluate patients with complex medical problems who are often taking many medications. Over the last several decades, many new drugs that target molecular pathways in carcinogenesis and the inflammatory immune system have been developed. Increased skin cancer risk has been reported in association with BRAF inhibitors, sonic hedgehog–inhibiting agents, Janus kinase (JAK) inhibitors, and phosphodiesterase 5 (PDE-5) inhibitors. We review the literature and data regarding the significance and strength of these associations and the molecular pathways by which these medications promote cutaneous tumorigenesis. The association of skin cancer with drugs that either induce photosensitivity—nonsteroidal anti-inflammatory drugs, antibiotics (eg, tetracyclines, fluoroquinolones, trimethoprim-sulfamethoxazole), voriconazole, thiazides—or suppress the immune system—certain biologics (eg, anti–tumor necrosis factor agents), calcineurin inhibitors, thiopurines, methotrexate, cyclosporine—is well known and is therefore not reviewed in this discussion.

BRAF Inhibitors

The mitogen-activated protein kinase (MAPK) pathway (also known as the RAS/RAF/MAPK signaling pathway) is important in growth factor–receptor signaling and plays a key role in cell differentiation, survival, and proliferation. Activating mutations in this pathway allow cells to grow and proliferate in a growth factor–independent manner. Twenty percent of human cancers harbor a mutation in the RAS oncogene, an upstream mediator of the pathway.1 Activating mutations in BRAF, a serine/threonine kinase, predominate in cutaneous melanoma and also have been found in 40% to 70% of papillary thyroid malignancies, 10% to 20% of cholangiocarcinomas, and 5% to 20% of colorectal carcinomas. The most common BRAF mutation in cutaneous melanoma is V600E, which involves a glutamic acid for valine substitution at codon 600. This mutation activates BRAF 500-fold and is present in approximately 50% of melanomas.1,2

Vemurafenib, a selective BRAF inhibitor, was approved by the US Food and Drug Administration (FDA) for the treatment of metastatic melanoma in the United States in 2011. Phase 3 trial data demonstrated that vemurafenib resulted in improved survival and decreased risk for disease progression compared to dacarbazine, the former best treatment.3 During phase 1 testing, it became apparent that vemurafenib treatment was associated with a 31% increased risk for squamous cell carcinoma (SCC), most commonly well-differentiated SCC, and keratoacanthomas (KAs).4 This association was confirmed in phase 2 and 3 studies, though the incidence was lower. McArthur et al5 reported a 19% incidence of cutaneous SCC with extended follow-up analysis of the phase 3 trial. Dabrafenib, another BRAF inhibitor, has been similarly associated with increasing the risk for SCC and KA.

In one study, the mean time to development of SCC after initiating vemurafenib therapy was 10 weeks, with lesions reported as early as 3 weeks. Most patients had clinical signs of chronically sun damaged skin; however, a history of SCC was present in only 17%. Most lesions (63%) were characterized as KAs.6

The mechanism for BRAF inhibitor–induced squamoproliferative growth is due to paradoxical activation of the MAPK pathway in cells with wild-type BRAF that harbor upstream-activating mutations in RAS or tyrosine kinase receptors.7 In the presence of a BRAF inhibitor, inactivated BRAF forms heterodimers with wild-type CRAF (a BRAF-CRAF heterodimer). The heterodimer forms a complex with the mutant RAS that leads to transactivation of the CRAF molecule,8,9 resulting in a paradoxical increase in MAPK signaling and consequent ERK phosphorylation and activation through CRAF signaling. RAS, particularly HRAS, mutations have been found in 60% of all vemurafenib-associated SCCs and KAs. For this reason, it is thought that vemurafenib potentiates tumorigenesis in subclinical lesions harboring upstream MAPK pathway mutations as opposed to inducing de novo lesions.6

Because BRAF inhibitors are remarkably efficacious in the treatment of metastatic melanomas harboring the V600E BRAF mutation, there are no restrictions on their use, despite the known increased risk for SCC. Squamous cell carcinomas tend to be low grade, and all tumors that developed in phase 1 to 3 trials were treated with simple excision. The development of SCC did not necessitate interruption of treatment. Furthermore, the addition of MEK inhibition to BRAF inhibitor therapy reduces the risk for SCC from 19% to 7%.7,10,11

In addition to SCC, second primary melanomas (SPMs) have been reported in patients treated with BRAF inhibitors. It has been shown that these melanomas occur in melanocytes with wild-type BRAF. It has been postulated that some of these tumors occur in cells that harbor upstream mutations in RAS, whereas others might result from alternate signaling through non-RAF oncogenic pathways.9,12



Zimmer et al1 reported 12 SPMs in 11 patients treated with BRAF inhibitor therapy. They reported a median delay of 8 weeks (range, 4–27 weeks) for SPM development. Tumors were detected in early stages; 1 tumor harbored an NRAS mutation.1

 

 


Dalle et al13 reported 25 SPMs in 120 vemurafenib-treated patients. Median delay in SPM development was 14 weeks (range, 4–42 weeks). All tumors were thin, ranging from in situ to 0.45-mm thick. Wild-type BRAF was detected in the 21 melanomas sampled; 1 lesion showed mutated NRAS.13



The exact incidence of SPM in the setting of BRAF inhibition is thought to be at least 10-fold less than SCC and KA.2 Patients on BRAF inhibitor therapy should have routine full-body skin examinations, given the increased risk for SPM and SCC.

Another drug belonging to the tyrosine kinase inhibitor family, sorafenib, is used in the treatment of solid tumors, particularly hepatocellular and renal cell carcinomas, and also has been associated with development of cutaneous SCC and KAs.14 Sorafenib is a multiple tyrosine kinase inhibitor that also inhibits the RAF serine/threonine kinases. Similar to vemurafenib and dabrafenib, SCCs and KAs associated with sorafenib tend to arise in patients with chronic actinic damage during the first 2 months of treatment. It has been hypothesized that inhibition of RAF kinases is pathogenic in inducing SCCs because these lesions have not been reported with sunitinib, another multiple tyrosine kinase inhibitor that lacks the ability to inhibit serine/threonine kinases.15,16 Although SCCs and KAs associated with sorafenib tend to be low grade, it is reasonable to consider sunitinib or an alternative tyrosine kinase inhibitor in patients who develop multiple SCCs while taking sorafenib.16

Sonic Hedgehog–Inhibiting Agents

Vismodegib, the first small molecule inhibitor of the signaling protein smoothened, gained FDA approval for the treatment of metastatic or locally advanced basal cell carcinoma (BCC) in 2012. A second agent with an identical mechanism of action, sonidegib, was approved by the FDA for locally advanced BCC in 2015. Approximately 90% of BCCs contain mutations in the sonic hedgehog pathway, which lead to constitutive smoothened activation and uncontrolled cell proliferation.17 The development of smoothened inhibitors introduced a much-needed treatment for inoperable or metastatic BCC,17,18 though long-term utility is limited by drug resistance with extended use in this patient population.19,20 Several case reports have documented the emergence of KA21 and cutaneous SCC following vismodegib treatment of advanced or metastatic BCC.22-24 A larger case-control study by Mohan et al25 showed that patients with BCC treated with vismodegib had an increased risk for non-BCC malignancy (hazard ratio [HR]=6.37), most of which were cutaneous SCC (HR=8.12).

The mechanism by which selective inhibition of smoothened leads to cutaneous SCC is unclear. A study found that patients on vismodegib who developed SCC within the original BCC site had elevated ERK levels within tumor tissue, suggesting that the RAS/RAF/MAPK pathway can become upregulated during hedgehog inhibition.26 Other studies looking at hedgehog inhibition in medulloblastoma models also have shown activated RAS/RAF/MAPK pathways.25 These findings suggest that tumors under smoothened inhibition might be able to bypass the sonic hedgehog pathway and continue to grow by upregulating alternative growth pathways, such as RAS/RAF/MAPK.25,26

The incidence of cutaneous SCC following vismodegib treatment is unknown. Chang and Oro27 examined BCC tumor regrowth from secondary (acquired) resistance to vismodegib and noted that lesions recurred within 1 cm of the original tumor 21% of the time. Although none of the 12 patients whose tumors regrew during treatment were reported to have developed SCC, several demonstrated different BCC subtypes than the pretreatment specimen. The authors proposed that regrowth of BCC was due to upregulated alternative pathways allowing tumors to bypass smoothened inhibition, which is similar to the proposed mechanism for SCC development in vismodegib patients.27



Prospective studies are needed to confirm the link between vismodegib and cutaneous SCC; establish the incidence of SCC development; and identify any pretreatment factors, tumor characteristics, or treatment details (eg, dosage, duration) that might contribute to SCC development. Furthermore, because Mohan et al25 observed that vismodegib-treated patients were less likely to develop SCC in situ than controls, it is unknown if these tumors are more aggressive than traditional SCC. At this point, careful surveillance and regular full-body skin examinations are advised for patients on vismodegib for treatment of advanced BCC.

 

 

JAK Inhibitors

Another class of medications potentially associated with increased development of nonmelanoma skin cancer (NMSC) is the JAK inhibitors (also known as jakinibs). Many proinflammatory signaling pathways converge on the JAK family of enzymes—JAK1, JAK2, JAK3, and TYK2. These enzymes operate in cytokine signal transduction by phosphorylating activated cytokine receptors, which allows for recruitment and activation by means of phosphorylation of transcription factors collectively known as signal transducers and activators of transcription (STATs). Phosphorylated STATs dimerize and translocate to the nucleus, acting as direct transcription promoters. Janus kinase inhibitors modulate the immune response by reducing the effect of interleukin and interferon signaling.

Ruxolitinib, a JAK1/JAK2 inhibitor, was the first JAK inhibitor approved by the FDA and is indicated for the treatment of myelofibrosis and polycythemia vera. Additionally, oral and topical JAK inhibitors have shown efficacy in the treatment of psoriasis, rheumatoid arthritis, alopecia areata, vitiligo, and pruritus from atopic dermatitis.28

The JAK-STAT pathway is complex, and the biological activity of the pathway is both proinflammatory and pro–cell survival and proliferation. Because signaling through the pathway can increase angiogenesis and inhibit apoptosis, inhibition of this pathway has been exploited for the treatment of some tumors. However, inhibition of interferon and proinflammatory interleukin signaling also can potentially promote tumor growth by means of inhibition of downstream cytotoxic T-cell signaling, theoretically increasing the risk for NMSC. A study examining the 5-year efficacy of ruxolitinib in myelofibrosis patients (COMFORT-II trial) found that 17.1% of patients developed NMSC compared to only 2.7% of those on the best available therapy. After adjustment by patient exposure, the NMSC rate was still doubled for ruxolitinib-treated patients compared to controls (6.1/100 patient-years and 3.0/100 patient-years, respectively).29 Eighty-week follow-up of the phase 3 clinical trial of ruxolitinib for the treatment of polycythemia vera also noted an increased incidence of NMSC, albeit a more conservative increase. Patients randomized to the ruxolitinib treatment group developed NMSC at a rate of 4.4/100 patient-years, whereas the rate for controls treated with best available therapy was 2.7/100 patient-years.30 In contrast, 5-year follow-up of the COMFORT-I trial, also examining the efficacy of ruxolitinib in myelofibrosis, showed no increased risk for NMSC between ruxolitinib-treated patients and placebo (2.7/100 patient-years and 3.9/100 patient-years, respectively).31

A 2017 case series described 5 patients with myelofibrosis who developed multiple skin cancers with aggressive features while receiving ruxolitinib.32 Duration of ruxolitinib therapy ranged from 4 months to 4 years; 3 patients had a history of hydroxyurea exposure, and only 1 patient had a history of NMSC. High-risk cutaneous SCC, undifferentiated pleomorphic sarcoma, and lentigo maligna melanoma (Breslow thickness, 0.45 mm) were among the tumors reported in this series. Although no definitive conclusion can be made regarding the causality of JAK inhibitors in promoting these tumors, the association warrants further investigation. Clinicians should be aware that ruxolitinib might amplify the risk for NMSC in patients with pre-existing genetic or exposure-related susceptibility. Interruption of drug therapy may be necessary in managing patients who develop an aggressive tumor.32

In contrast, tofacitinib, which specifically inhibits JAK3, carries very low risk, if any, for NMSC when used for the treatment of psoriasis and rheumatoid arthritis. Results from 2 phase 3 trials analyzing the efficacy of tofacitinib in psoriasis demonstrated that only 2 of 1486 patients treated developed NMSC compared to none in the control group.33 Furthermore, analysis of NMSC across the tofacitinib rheumatoid arthritis clinical program, which included a total of 15,103 patient-years of exposure, demonstrated that the overall NMSC incidence was 0.55 for every 100 patient-years. Of note, the risk in patients receiving high-dose treatment (10 mg vs 5 mg) was nearly doubled in long-term follow-up studies (0.79/100 patient-years and 0.41/100 patient-years, respectively). Overall, the study concluded that treatment with tofacitinib presents no greater increased risk for NMSC than treatment with tumor necrosis factor inhibitors.33

PDE-5 Inhibitors

Phosphodiesterase 5 inhibitors, such as sildenafil citrate, have been widely prescribed for the treatment of erectile dysfunction. Studies have shown that BRAF-activated melanomas, which occur in approximately 50% to 70% of melanomas, also result in reduced PDE-5 expression.34-36 In these melanomas, downregulation of PDE-5 results in increased intracellular calcium,36 which has been shown to induce melanoma invasion.36,37 Given this similarity in molecular pathway between BRAF-activated melanomas and PDE-5 inhibitors, there has been increased concern that PDE-5 inhibitors might be associated with an increased risk for melanoma.

In 2014, Li et al38 published a retrospective analysis suggesting an association with sildenafil and an increased risk for melanoma. Their study utilized the Health Professionals Follow-up Study to identify a statistically significant elevation in the risk for invasive melanoma with both recent sildenafil use (multivariate-adjusted HR=2.24) and use at any time (HR=1.92). These results controlled for confounding variables, such as presence of major chronic disease, use of other erectile dysfunction treatments, family history of melanoma, history of sun exposure, and UV index of the patient’s residence. Notably, the study also found that sildenafil did not affect the incidence of BCC or SCC.38

 

 

In 2015, Loeb et al39 also examined the potential association between PDE-5 inhibitors and melanoma. Review of several Swedish drug and cancer registries allowed for analysis of melanoma risk and PDE-5 inhibitor use, based on number of prescriptions filled and type of PDE-5 inhibitor prescribed. Their analysis showed that men developing melanoma were more likely than nonmelanoma controls to have taken a PDE-5 inhibitor (11% vs 8%). In a subgroup analysis, however, statistical significance was shown for men with only a single prescription filled (34% of cases; P<.05), whereas the difference for men with multiple filled prescriptions did not meet statistical significance. Furthermore, the study did not find increased risk with longer-acting tadalafil and vardenafil (odds ratio [OR]=1.16) compared to sildenafil (OR=1.14). Last, use of PDE-5 inhibitors was only associated with stage 0 (OR=1.49) and stage I (OR=1.21) tumors, not with stages II to IV (OR=0.83) tumors. Although there was a statistically significant association between PDE-5 inhibitors and malignant melanoma (P<.05), the subgroup analysis findings pointed away from a causal relationship and likely toward a confounding of variable(s).39



A 2016 study by Lian et al40 looked at the risk for melanoma in a cohort of patients diagnosed with erectile dysfunction. No association between PDE-5 inhibitors and melanoma risk was shown when comparing patients who received a PDE-5 inhibitor and those who did not receive a PDE-5 inhibitor. However, secondary analysis did show that melanoma risk was increased among patients receiving more pills (34%) and prescriptions (30%). The authors concluded that there was no association between PDE-5 inhibitor use and overall increased risk for melanoma, and the increased risk associated with a greater number of pills and prescriptions would require further study.40

In contrast, a 2017 meta-analysis by Tang et al41 of 5 studies (3 of which were the aforementioned trials38-40) concluded that use of PDE-5 inhibitors was associated with a small but significantly increased risk for melanoma (OR=1.12) and BCC (OR=1.14) but not SCC. Furthermore, the study found no evidence of dosage-dependent association between PDE-5 inhibitor use and melanoma risk.41



Overall, clinical studies have been inconclusive in determining the risk for melanoma in the setting of PDE-5 inhibitor use. Studies showing an increased rate of melanoma within patient cohorts receiving PDE-5 inhibitors are limited; results might be affected by confounding variables. However, given the similarity in mechanism between PDE-5 inhibitors and HRAS-activated melanomas, it is reasonable to continue research into this potential association.

Conclusion

Since the turn of the century, drugs targeting cell-signaling pathways have been developed to treat inflammatory, oncologic, and immune conditions. The role of immunosuppressants in promoting skin cancer is well established and supported by a vast literature base. However, associations are less clear with newer immunomodulatory and antineoplastic medications. Skin cancer has been reported in association with BRAF inhibitors, sonic hedgehog–inhibiting agents, JAK inhibitors, and PDE-5 inhibitors. In the case of JAK and PDE-5 inhibitors, the increased risk for melanoma and NMSC is somewhat inconclusive; risk is more firmly established for BRAF inhibitors and smoothened inhibitors. For the antineoplastic agents reviewed, the therapeutic effect of cancer regression is well documented, and benefits of continued therapy outweigh the increased risk for skin cancer promotion in nearly all cases. The value of early detection has been well documented for skin malignancy; therefore, increased skin surveillance and prompt management of suspicious lesions should be a priority for physicians treating patients undergoing therapy with these medications

Dermatologists are increasingly called on to evaluate patients with complex medical problems who are often taking many medications. Over the last several decades, many new drugs that target molecular pathways in carcinogenesis and the inflammatory immune system have been developed. Increased skin cancer risk has been reported in association with BRAF inhibitors, sonic hedgehog–inhibiting agents, Janus kinase (JAK) inhibitors, and phosphodiesterase 5 (PDE-5) inhibitors. We review the literature and data regarding the significance and strength of these associations and the molecular pathways by which these medications promote cutaneous tumorigenesis. The association of skin cancer with drugs that either induce photosensitivity—nonsteroidal anti-inflammatory drugs, antibiotics (eg, tetracyclines, fluoroquinolones, trimethoprim-sulfamethoxazole), voriconazole, thiazides—or suppress the immune system—certain biologics (eg, anti–tumor necrosis factor agents), calcineurin inhibitors, thiopurines, methotrexate, cyclosporine—is well known and is therefore not reviewed in this discussion.

BRAF Inhibitors

The mitogen-activated protein kinase (MAPK) pathway (also known as the RAS/RAF/MAPK signaling pathway) is important in growth factor–receptor signaling and plays a key role in cell differentiation, survival, and proliferation. Activating mutations in this pathway allow cells to grow and proliferate in a growth factor–independent manner. Twenty percent of human cancers harbor a mutation in the RAS oncogene, an upstream mediator of the pathway.1 Activating mutations in BRAF, a serine/threonine kinase, predominate in cutaneous melanoma and also have been found in 40% to 70% of papillary thyroid malignancies, 10% to 20% of cholangiocarcinomas, and 5% to 20% of colorectal carcinomas. The most common BRAF mutation in cutaneous melanoma is V600E, which involves a glutamic acid for valine substitution at codon 600. This mutation activates BRAF 500-fold and is present in approximately 50% of melanomas.1,2

Vemurafenib, a selective BRAF inhibitor, was approved by the US Food and Drug Administration (FDA) for the treatment of metastatic melanoma in the United States in 2011. Phase 3 trial data demonstrated that vemurafenib resulted in improved survival and decreased risk for disease progression compared to dacarbazine, the former best treatment.3 During phase 1 testing, it became apparent that vemurafenib treatment was associated with a 31% increased risk for squamous cell carcinoma (SCC), most commonly well-differentiated SCC, and keratoacanthomas (KAs).4 This association was confirmed in phase 2 and 3 studies, though the incidence was lower. McArthur et al5 reported a 19% incidence of cutaneous SCC with extended follow-up analysis of the phase 3 trial. Dabrafenib, another BRAF inhibitor, has been similarly associated with increasing the risk for SCC and KA.

In one study, the mean time to development of SCC after initiating vemurafenib therapy was 10 weeks, with lesions reported as early as 3 weeks. Most patients had clinical signs of chronically sun damaged skin; however, a history of SCC was present in only 17%. Most lesions (63%) were characterized as KAs.6

The mechanism for BRAF inhibitor–induced squamoproliferative growth is due to paradoxical activation of the MAPK pathway in cells with wild-type BRAF that harbor upstream-activating mutations in RAS or tyrosine kinase receptors.7 In the presence of a BRAF inhibitor, inactivated BRAF forms heterodimers with wild-type CRAF (a BRAF-CRAF heterodimer). The heterodimer forms a complex with the mutant RAS that leads to transactivation of the CRAF molecule,8,9 resulting in a paradoxical increase in MAPK signaling and consequent ERK phosphorylation and activation through CRAF signaling. RAS, particularly HRAS, mutations have been found in 60% of all vemurafenib-associated SCCs and KAs. For this reason, it is thought that vemurafenib potentiates tumorigenesis in subclinical lesions harboring upstream MAPK pathway mutations as opposed to inducing de novo lesions.6

Because BRAF inhibitors are remarkably efficacious in the treatment of metastatic melanomas harboring the V600E BRAF mutation, there are no restrictions on their use, despite the known increased risk for SCC. Squamous cell carcinomas tend to be low grade, and all tumors that developed in phase 1 to 3 trials were treated with simple excision. The development of SCC did not necessitate interruption of treatment. Furthermore, the addition of MEK inhibition to BRAF inhibitor therapy reduces the risk for SCC from 19% to 7%.7,10,11

In addition to SCC, second primary melanomas (SPMs) have been reported in patients treated with BRAF inhibitors. It has been shown that these melanomas occur in melanocytes with wild-type BRAF. It has been postulated that some of these tumors occur in cells that harbor upstream mutations in RAS, whereas others might result from alternate signaling through non-RAF oncogenic pathways.9,12



Zimmer et al1 reported 12 SPMs in 11 patients treated with BRAF inhibitor therapy. They reported a median delay of 8 weeks (range, 4–27 weeks) for SPM development. Tumors were detected in early stages; 1 tumor harbored an NRAS mutation.1

 

 


Dalle et al13 reported 25 SPMs in 120 vemurafenib-treated patients. Median delay in SPM development was 14 weeks (range, 4–42 weeks). All tumors were thin, ranging from in situ to 0.45-mm thick. Wild-type BRAF was detected in the 21 melanomas sampled; 1 lesion showed mutated NRAS.13



The exact incidence of SPM in the setting of BRAF inhibition is thought to be at least 10-fold less than SCC and KA.2 Patients on BRAF inhibitor therapy should have routine full-body skin examinations, given the increased risk for SPM and SCC.

Another drug belonging to the tyrosine kinase inhibitor family, sorafenib, is used in the treatment of solid tumors, particularly hepatocellular and renal cell carcinomas, and also has been associated with development of cutaneous SCC and KAs.14 Sorafenib is a multiple tyrosine kinase inhibitor that also inhibits the RAF serine/threonine kinases. Similar to vemurafenib and dabrafenib, SCCs and KAs associated with sorafenib tend to arise in patients with chronic actinic damage during the first 2 months of treatment. It has been hypothesized that inhibition of RAF kinases is pathogenic in inducing SCCs because these lesions have not been reported with sunitinib, another multiple tyrosine kinase inhibitor that lacks the ability to inhibit serine/threonine kinases.15,16 Although SCCs and KAs associated with sorafenib tend to be low grade, it is reasonable to consider sunitinib or an alternative tyrosine kinase inhibitor in patients who develop multiple SCCs while taking sorafenib.16

Sonic Hedgehog–Inhibiting Agents

Vismodegib, the first small molecule inhibitor of the signaling protein smoothened, gained FDA approval for the treatment of metastatic or locally advanced basal cell carcinoma (BCC) in 2012. A second agent with an identical mechanism of action, sonidegib, was approved by the FDA for locally advanced BCC in 2015. Approximately 90% of BCCs contain mutations in the sonic hedgehog pathway, which lead to constitutive smoothened activation and uncontrolled cell proliferation.17 The development of smoothened inhibitors introduced a much-needed treatment for inoperable or metastatic BCC,17,18 though long-term utility is limited by drug resistance with extended use in this patient population.19,20 Several case reports have documented the emergence of KA21 and cutaneous SCC following vismodegib treatment of advanced or metastatic BCC.22-24 A larger case-control study by Mohan et al25 showed that patients with BCC treated with vismodegib had an increased risk for non-BCC malignancy (hazard ratio [HR]=6.37), most of which were cutaneous SCC (HR=8.12).

The mechanism by which selective inhibition of smoothened leads to cutaneous SCC is unclear. A study found that patients on vismodegib who developed SCC within the original BCC site had elevated ERK levels within tumor tissue, suggesting that the RAS/RAF/MAPK pathway can become upregulated during hedgehog inhibition.26 Other studies looking at hedgehog inhibition in medulloblastoma models also have shown activated RAS/RAF/MAPK pathways.25 These findings suggest that tumors under smoothened inhibition might be able to bypass the sonic hedgehog pathway and continue to grow by upregulating alternative growth pathways, such as RAS/RAF/MAPK.25,26

The incidence of cutaneous SCC following vismodegib treatment is unknown. Chang and Oro27 examined BCC tumor regrowth from secondary (acquired) resistance to vismodegib and noted that lesions recurred within 1 cm of the original tumor 21% of the time. Although none of the 12 patients whose tumors regrew during treatment were reported to have developed SCC, several demonstrated different BCC subtypes than the pretreatment specimen. The authors proposed that regrowth of BCC was due to upregulated alternative pathways allowing tumors to bypass smoothened inhibition, which is similar to the proposed mechanism for SCC development in vismodegib patients.27



Prospective studies are needed to confirm the link between vismodegib and cutaneous SCC; establish the incidence of SCC development; and identify any pretreatment factors, tumor characteristics, or treatment details (eg, dosage, duration) that might contribute to SCC development. Furthermore, because Mohan et al25 observed that vismodegib-treated patients were less likely to develop SCC in situ than controls, it is unknown if these tumors are more aggressive than traditional SCC. At this point, careful surveillance and regular full-body skin examinations are advised for patients on vismodegib for treatment of advanced BCC.

 

 

JAK Inhibitors

Another class of medications potentially associated with increased development of nonmelanoma skin cancer (NMSC) is the JAK inhibitors (also known as jakinibs). Many proinflammatory signaling pathways converge on the JAK family of enzymes—JAK1, JAK2, JAK3, and TYK2. These enzymes operate in cytokine signal transduction by phosphorylating activated cytokine receptors, which allows for recruitment and activation by means of phosphorylation of transcription factors collectively known as signal transducers and activators of transcription (STATs). Phosphorylated STATs dimerize and translocate to the nucleus, acting as direct transcription promoters. Janus kinase inhibitors modulate the immune response by reducing the effect of interleukin and interferon signaling.

Ruxolitinib, a JAK1/JAK2 inhibitor, was the first JAK inhibitor approved by the FDA and is indicated for the treatment of myelofibrosis and polycythemia vera. Additionally, oral and topical JAK inhibitors have shown efficacy in the treatment of psoriasis, rheumatoid arthritis, alopecia areata, vitiligo, and pruritus from atopic dermatitis.28

The JAK-STAT pathway is complex, and the biological activity of the pathway is both proinflammatory and pro–cell survival and proliferation. Because signaling through the pathway can increase angiogenesis and inhibit apoptosis, inhibition of this pathway has been exploited for the treatment of some tumors. However, inhibition of interferon and proinflammatory interleukin signaling also can potentially promote tumor growth by means of inhibition of downstream cytotoxic T-cell signaling, theoretically increasing the risk for NMSC. A study examining the 5-year efficacy of ruxolitinib in myelofibrosis patients (COMFORT-II trial) found that 17.1% of patients developed NMSC compared to only 2.7% of those on the best available therapy. After adjustment by patient exposure, the NMSC rate was still doubled for ruxolitinib-treated patients compared to controls (6.1/100 patient-years and 3.0/100 patient-years, respectively).29 Eighty-week follow-up of the phase 3 clinical trial of ruxolitinib for the treatment of polycythemia vera also noted an increased incidence of NMSC, albeit a more conservative increase. Patients randomized to the ruxolitinib treatment group developed NMSC at a rate of 4.4/100 patient-years, whereas the rate for controls treated with best available therapy was 2.7/100 patient-years.30 In contrast, 5-year follow-up of the COMFORT-I trial, also examining the efficacy of ruxolitinib in myelofibrosis, showed no increased risk for NMSC between ruxolitinib-treated patients and placebo (2.7/100 patient-years and 3.9/100 patient-years, respectively).31

A 2017 case series described 5 patients with myelofibrosis who developed multiple skin cancers with aggressive features while receiving ruxolitinib.32 Duration of ruxolitinib therapy ranged from 4 months to 4 years; 3 patients had a history of hydroxyurea exposure, and only 1 patient had a history of NMSC. High-risk cutaneous SCC, undifferentiated pleomorphic sarcoma, and lentigo maligna melanoma (Breslow thickness, 0.45 mm) were among the tumors reported in this series. Although no definitive conclusion can be made regarding the causality of JAK inhibitors in promoting these tumors, the association warrants further investigation. Clinicians should be aware that ruxolitinib might amplify the risk for NMSC in patients with pre-existing genetic or exposure-related susceptibility. Interruption of drug therapy may be necessary in managing patients who develop an aggressive tumor.32

In contrast, tofacitinib, which specifically inhibits JAK3, carries very low risk, if any, for NMSC when used for the treatment of psoriasis and rheumatoid arthritis. Results from 2 phase 3 trials analyzing the efficacy of tofacitinib in psoriasis demonstrated that only 2 of 1486 patients treated developed NMSC compared to none in the control group.33 Furthermore, analysis of NMSC across the tofacitinib rheumatoid arthritis clinical program, which included a total of 15,103 patient-years of exposure, demonstrated that the overall NMSC incidence was 0.55 for every 100 patient-years. Of note, the risk in patients receiving high-dose treatment (10 mg vs 5 mg) was nearly doubled in long-term follow-up studies (0.79/100 patient-years and 0.41/100 patient-years, respectively). Overall, the study concluded that treatment with tofacitinib presents no greater increased risk for NMSC than treatment with tumor necrosis factor inhibitors.33

PDE-5 Inhibitors

Phosphodiesterase 5 inhibitors, such as sildenafil citrate, have been widely prescribed for the treatment of erectile dysfunction. Studies have shown that BRAF-activated melanomas, which occur in approximately 50% to 70% of melanomas, also result in reduced PDE-5 expression.34-36 In these melanomas, downregulation of PDE-5 results in increased intracellular calcium,36 which has been shown to induce melanoma invasion.36,37 Given this similarity in molecular pathway between BRAF-activated melanomas and PDE-5 inhibitors, there has been increased concern that PDE-5 inhibitors might be associated with an increased risk for melanoma.

In 2014, Li et al38 published a retrospective analysis suggesting an association with sildenafil and an increased risk for melanoma. Their study utilized the Health Professionals Follow-up Study to identify a statistically significant elevation in the risk for invasive melanoma with both recent sildenafil use (multivariate-adjusted HR=2.24) and use at any time (HR=1.92). These results controlled for confounding variables, such as presence of major chronic disease, use of other erectile dysfunction treatments, family history of melanoma, history of sun exposure, and UV index of the patient’s residence. Notably, the study also found that sildenafil did not affect the incidence of BCC or SCC.38

 

 

In 2015, Loeb et al39 also examined the potential association between PDE-5 inhibitors and melanoma. Review of several Swedish drug and cancer registries allowed for analysis of melanoma risk and PDE-5 inhibitor use, based on number of prescriptions filled and type of PDE-5 inhibitor prescribed. Their analysis showed that men developing melanoma were more likely than nonmelanoma controls to have taken a PDE-5 inhibitor (11% vs 8%). In a subgroup analysis, however, statistical significance was shown for men with only a single prescription filled (34% of cases; P<.05), whereas the difference for men with multiple filled prescriptions did not meet statistical significance. Furthermore, the study did not find increased risk with longer-acting tadalafil and vardenafil (odds ratio [OR]=1.16) compared to sildenafil (OR=1.14). Last, use of PDE-5 inhibitors was only associated with stage 0 (OR=1.49) and stage I (OR=1.21) tumors, not with stages II to IV (OR=0.83) tumors. Although there was a statistically significant association between PDE-5 inhibitors and malignant melanoma (P<.05), the subgroup analysis findings pointed away from a causal relationship and likely toward a confounding of variable(s).39



A 2016 study by Lian et al40 looked at the risk for melanoma in a cohort of patients diagnosed with erectile dysfunction. No association between PDE-5 inhibitors and melanoma risk was shown when comparing patients who received a PDE-5 inhibitor and those who did not receive a PDE-5 inhibitor. However, secondary analysis did show that melanoma risk was increased among patients receiving more pills (34%) and prescriptions (30%). The authors concluded that there was no association between PDE-5 inhibitor use and overall increased risk for melanoma, and the increased risk associated with a greater number of pills and prescriptions would require further study.40

In contrast, a 2017 meta-analysis by Tang et al41 of 5 studies (3 of which were the aforementioned trials38-40) concluded that use of PDE-5 inhibitors was associated with a small but significantly increased risk for melanoma (OR=1.12) and BCC (OR=1.14) but not SCC. Furthermore, the study found no evidence of dosage-dependent association between PDE-5 inhibitor use and melanoma risk.41



Overall, clinical studies have been inconclusive in determining the risk for melanoma in the setting of PDE-5 inhibitor use. Studies showing an increased rate of melanoma within patient cohorts receiving PDE-5 inhibitors are limited; results might be affected by confounding variables. However, given the similarity in mechanism between PDE-5 inhibitors and HRAS-activated melanomas, it is reasonable to continue research into this potential association.

Conclusion

Since the turn of the century, drugs targeting cell-signaling pathways have been developed to treat inflammatory, oncologic, and immune conditions. The role of immunosuppressants in promoting skin cancer is well established and supported by a vast literature base. However, associations are less clear with newer immunomodulatory and antineoplastic medications. Skin cancer has been reported in association with BRAF inhibitors, sonic hedgehog–inhibiting agents, JAK inhibitors, and PDE-5 inhibitors. In the case of JAK and PDE-5 inhibitors, the increased risk for melanoma and NMSC is somewhat inconclusive; risk is more firmly established for BRAF inhibitors and smoothened inhibitors. For the antineoplastic agents reviewed, the therapeutic effect of cancer regression is well documented, and benefits of continued therapy outweigh the increased risk for skin cancer promotion in nearly all cases. The value of early detection has been well documented for skin malignancy; therefore, increased skin surveillance and prompt management of suspicious lesions should be a priority for physicians treating patients undergoing therapy with these medications

References
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  2. Long GV, Menzies AM, Nagrial AM, et al. Prognostic and clinicopathologic associations of oncogenic BRAF in metastatic melanoma. J Clin Oncol. 2011;29:1239-1246.
  3. Chapman PB, Hauschild A, Robert C, et al; BRIM-3 Study Group. Improved survival with vemurafenib in melanoma with BRAF V600E mutation. N Engl J Med. 2011;364:2507-2516.
  4. Flaherty KT, Puzanov I, Kim KB, et al. Inhibition of mutated, activated BRAF in metastatic melanoma. N Engl J Med. 2010;363:809-819.
  5. McArthur GA, Chapman PB, Robert C, et al. Safety and efficacy of vemurafenib in BRAF(V600E) and BRAF(V600K) mutation-positive melanoma (BRIM-3): extended follow-up of a phase 3, randomised, open-label study. Lancet Oncol. 2014;15:323-332.
  6. Su F, Viros A, Milagre C, et al. RAS mutations in cutaneous squamous-cell carcinomas in patients treated with BRAF inhibitors. N Engl J Med. 2012;366:207-215.
  7. Carlos G, Anforth R, Clements A, et al. Cutaneous toxic effects of BRAF inhibitors alone and in combination with MEK inhibitors for metastatic melanoma. JAMA Dermatol. 2015;151:1103-1109.
  8. Poulikakos PI, Zhang C, Bollag G, et al. RAF inhibitors transactivate RAF dimers and ERK signalling in cells with wild-type BRAF. Nature. 2010;464:427-430.
  9. Ryan MB, Der CJ, Wang-Gillam A, et al. Targeting RAS-mutant cancers: is ERK the key? Trends Cancer. 2015;1:183-198.
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  11. Robert C, Karaszewska B, Schachter J, et al. Improved overall survival in melanoma with combined dabrafenib and trametinib. N Engl J Med. 2015;372:30-39.
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  13. Dalle S, Poulalhon N, Debarbieux S, et al. Tracking of second primary melanomas in vemurafenib-treated patients. JAMA Dermatol. 2013;149:488-490.
  14. Williams VL, Cohen PR, Stewart DJ. Sorafenib-induced premalignant and malignant skin lesions. Int J Dermatol. 2011;50:396-402.
  15. Arnault JP, Wechsler J, Escudier B, et al. Keratoacanthomas and squamous cell carcinomas in patients receiving sorafenib. J Clin Oncol. 2009;27:e59-e61.
  16. Smith KJ, Haley H, Hamza S, et al. Eruptive keratoacanthoma-type squamous cell carcinomas in patients taking sorafenib for the treatment of solid tumors. Dermatol Surg. 2009;35:1766-1770.
  17. Sekulic A, Migden MR, Oro AE, et al. Efficacy and safety of vismodegib in advanced basal-cell carcinoma. N Engl J Med. 2012;366:2171-2179.
  18. Demirci H, Worden F, Nelson CC, et al. Efficacy of vismodegib (Erivedge) for basal cell carcinoma involving the orbit and periocular area. Ophthalmic Plast Reconstr Surg. 2015;31:463-466.
  19. Atwood SX, Sarin KY, Whitson RJ, et al. Smoothened variants explain the majority of drug resistance in basal cell carcinoma. Cancer Cell. 2015;27:342-353.
  20. Ridky TW, Cotsarelis G. Vismodegib resistance in basal cell carcinoma: not a smooth fit. Cancer Cell. 2015;27:315-316.
  21. Aasi S, Silkiss R, Tang JY, et al. New onset of keratoacanthomas after vismodegib treatment for locally advanced basal cell carcinomas: a report of 2 cases. JAMA Dermatol. 2013;149:242-243.
  22. Orouji A, Goerdt S, Utikal J, et al. Multiple highly and moderately differentiated squamous cell carcinomas of the skin during vismodegib treatment of inoperable basal cell carcinoma. Br J Dermatol. 2014;171:431-433.
  23. Iarrobino A, Messina JL, Kudchadkar R, et al. Emergence of a squamous cell carcinoma phenotype following treatment of metastatic basal cell carcinoma with vismodegib. J Am Acad Dermatol. 2013;69:e33-e34.
  24. Saintes C, Saint-Jean M, Brocard A, et al. Development of squamous cell carcinoma into basal cell carcinoma under treatment with vismodegib. J Eur Acad Dermatol Venereol. 2015;29:1006-1009.
  25. Mohan SV, Chang J, Li S, et al. Increased risk of cutaneous squamous cell carcinoma after vismodegib therapy for basal cell carcinoma. JAMA Dermatol. 2016;152:527-532.
  26. Zhao X, Ponomaryov T, Ornell KJ, et al. RAS/MAPK activation drives resistance to Smo inhibition, metastasis, and tumor evolution in Shh pathway-dependent tumors. Cancer Res. 2015;75:3623-3635.
  27. Chang AL, Oro AE. Initial assessment of tumor regrowth after vismodegib in advanced basal cell carcinoma. Arch Dermatol. 2012;148:1324-1325.
  28. Damsky W, King BA. JAK inhibitors in dermatology: the promise of a new drug class. J Am Acad Dermatol. 2017;76:736-744.
  29. Harrison CN, Vannucchi AM, Kiladjian JJ, et al. Long-term findings from COMFORT-II, a phase 3 study of ruxolitinib vs best available therapy for myelofibrosis. Leukemia. 2016;30:1701-1707.
  30. Verstovsek S, Vannucchi AM, Griesshammer M, et al. Ruxolitinib versus best available therapy in patients with polycythemia vera: 80-week follow-up from the RESPONSE trial. Haematologica. 2016;101:821-829.
  31. Verstovsek S, Mesa RA, Gotlib J, et al; COMFORT-I investigators. Long-term treatment with ruxolitinib for patients with myelofibrosis: 5-year update from the randomized, double-blind, placebo-controlled, phase 3 COMFORT-I trial. J Hematol Oncol. 2017;10:55.
  32. Blechman AB, Cabell CE, Weinberger CH, et al. Aggressive skin cancers occurring in patients treated with the Janus kinase inhibitor ruxolitinib. J Drugs Dermatol. 2017;16:508-511.
  33. Papp KA, Menter MA, Abe M, et al; OPT Pivotal 1 and OPT Pivotal 2 investigators. Tofacitinib, an oral Janus kinase inhibitor, for the treatment of chronic plaque psoriasis: results from two randomized, placebo-controlled, phase III trials. Br J Dermatol. 2015;173:949-961.
  34. Wellbrock C, Karasarides M, Marais R. The RAF proteins take centre stage. Nat Rev Mol Cell Biol. 2004;5:875-885.
  35. Gray-Schopfer V, Wellbrock C, Marais R. Melanoma biology and new targeted therapy. Nature. 2007;445:851-857.
  36. Arozarena I, Sanchez-Laorden B, Packer L, et al. Oncogenic BRAF induces melanoma cell invasion by downregulating the cGMP-specific phosphodiesterase PDE5A. Cancer Cell. 2011;19:45-57.
  37. Houslay MD. Hard times for oncogenic BRAF-expressing melanoma cells. Cancer Cell. 2011;19:3-4.
  38. Li WQ, Qureshi AA, Robinson KC, et al. Sildenafil use and increased risk of incident melanoma in US men: a prospective cohort study. JAMA Intern Med. 2014;174:964-970.
  39. Loeb S, Folkvaljon Y, Lambe M, et al. Use of phosphodiesterase type 5 inhibitors for erectile dysfunction and risk of malignant melanoma. JAMA. 2015;313:2449-2455.
  40. Lian Y, Yin H, Pollak MN, et al. Phosphodiesterase type 5 inhibitors and the risk of melanoma skin cancer. Eur Urol. 2016;70:808-815.
  41. Tang H, Wu W, Fu S, et al. Phosphodiesterase type 5 inhibitors and risk of melanoma: a meta-analysis. J Am Acad Dermatol. 2017;77:480.e9-488.e9.
References
  1. Zimmer L, Hillen U, Livingstone E, et al. Atypical melanocytic proliferations and new primary melanoma in patients with advanced melanoma undergoing selective BRAF inhibition. J Clin Oncol. 2012;30:2375-2383.
  2. Long GV, Menzies AM, Nagrial AM, et al. Prognostic and clinicopathologic associations of oncogenic BRAF in metastatic melanoma. J Clin Oncol. 2011;29:1239-1246.
  3. Chapman PB, Hauschild A, Robert C, et al; BRIM-3 Study Group. Improved survival with vemurafenib in melanoma with BRAF V600E mutation. N Engl J Med. 2011;364:2507-2516.
  4. Flaherty KT, Puzanov I, Kim KB, et al. Inhibition of mutated, activated BRAF in metastatic melanoma. N Engl J Med. 2010;363:809-819.
  5. McArthur GA, Chapman PB, Robert C, et al. Safety and efficacy of vemurafenib in BRAF(V600E) and BRAF(V600K) mutation-positive melanoma (BRIM-3): extended follow-up of a phase 3, randomised, open-label study. Lancet Oncol. 2014;15:323-332.
  6. Su F, Viros A, Milagre C, et al. RAS mutations in cutaneous squamous-cell carcinomas in patients treated with BRAF inhibitors. N Engl J Med. 2012;366:207-215.
  7. Carlos G, Anforth R, Clements A, et al. Cutaneous toxic effects of BRAF inhibitors alone and in combination with MEK inhibitors for metastatic melanoma. JAMA Dermatol. 2015;151:1103-1109.
  8. Poulikakos PI, Zhang C, Bollag G, et al. RAF inhibitors transactivate RAF dimers and ERK signalling in cells with wild-type BRAF. Nature. 2010;464:427-430.
  9. Ryan MB, Der CJ, Wang-Gillam A, et al. Targeting RAS-mutant cancers: is ERK the key? Trends Cancer. 2015;1:183-198.
  10. Long GV, Stroyakovskiy D, Gogas H, et al. Combined BRAF and MEK inhibition versus BRAF inhibition alone in melanoma. N Engl J Med. 2014;371:1877-1888.
  11. Robert C, Karaszewska B, Schachter J, et al. Improved overall survival in melanoma with combined dabrafenib and trametinib. N Engl J Med. 2015;372:30-39.
  12. Holderfield M, Nagel TE, Stuart DD. Mechanism and consequence of RAF kinase activation by small-molecule inhibitors. Br J Cancer. 2014;111:640-645.
  13. Dalle S, Poulalhon N, Debarbieux S, et al. Tracking of second primary melanomas in vemurafenib-treated patients. JAMA Dermatol. 2013;149:488-490.
  14. Williams VL, Cohen PR, Stewart DJ. Sorafenib-induced premalignant and malignant skin lesions. Int J Dermatol. 2011;50:396-402.
  15. Arnault JP, Wechsler J, Escudier B, et al. Keratoacanthomas and squamous cell carcinomas in patients receiving sorafenib. J Clin Oncol. 2009;27:e59-e61.
  16. Smith KJ, Haley H, Hamza S, et al. Eruptive keratoacanthoma-type squamous cell carcinomas in patients taking sorafenib for the treatment of solid tumors. Dermatol Surg. 2009;35:1766-1770.
  17. Sekulic A, Migden MR, Oro AE, et al. Efficacy and safety of vismodegib in advanced basal-cell carcinoma. N Engl J Med. 2012;366:2171-2179.
  18. Demirci H, Worden F, Nelson CC, et al. Efficacy of vismodegib (Erivedge) for basal cell carcinoma involving the orbit and periocular area. Ophthalmic Plast Reconstr Surg. 2015;31:463-466.
  19. Atwood SX, Sarin KY, Whitson RJ, et al. Smoothened variants explain the majority of drug resistance in basal cell carcinoma. Cancer Cell. 2015;27:342-353.
  20. Ridky TW, Cotsarelis G. Vismodegib resistance in basal cell carcinoma: not a smooth fit. Cancer Cell. 2015;27:315-316.
  21. Aasi S, Silkiss R, Tang JY, et al. New onset of keratoacanthomas after vismodegib treatment for locally advanced basal cell carcinomas: a report of 2 cases. JAMA Dermatol. 2013;149:242-243.
  22. Orouji A, Goerdt S, Utikal J, et al. Multiple highly and moderately differentiated squamous cell carcinomas of the skin during vismodegib treatment of inoperable basal cell carcinoma. Br J Dermatol. 2014;171:431-433.
  23. Iarrobino A, Messina JL, Kudchadkar R, et al. Emergence of a squamous cell carcinoma phenotype following treatment of metastatic basal cell carcinoma with vismodegib. J Am Acad Dermatol. 2013;69:e33-e34.
  24. Saintes C, Saint-Jean M, Brocard A, et al. Development of squamous cell carcinoma into basal cell carcinoma under treatment with vismodegib. J Eur Acad Dermatol Venereol. 2015;29:1006-1009.
  25. Mohan SV, Chang J, Li S, et al. Increased risk of cutaneous squamous cell carcinoma after vismodegib therapy for basal cell carcinoma. JAMA Dermatol. 2016;152:527-532.
  26. Zhao X, Ponomaryov T, Ornell KJ, et al. RAS/MAPK activation drives resistance to Smo inhibition, metastasis, and tumor evolution in Shh pathway-dependent tumors. Cancer Res. 2015;75:3623-3635.
  27. Chang AL, Oro AE. Initial assessment of tumor regrowth after vismodegib in advanced basal cell carcinoma. Arch Dermatol. 2012;148:1324-1325.
  28. Damsky W, King BA. JAK inhibitors in dermatology: the promise of a new drug class. J Am Acad Dermatol. 2017;76:736-744.
  29. Harrison CN, Vannucchi AM, Kiladjian JJ, et al. Long-term findings from COMFORT-II, a phase 3 study of ruxolitinib vs best available therapy for myelofibrosis. Leukemia. 2016;30:1701-1707.
  30. Verstovsek S, Vannucchi AM, Griesshammer M, et al. Ruxolitinib versus best available therapy in patients with polycythemia vera: 80-week follow-up from the RESPONSE trial. Haematologica. 2016;101:821-829.
  31. Verstovsek S, Mesa RA, Gotlib J, et al; COMFORT-I investigators. Long-term treatment with ruxolitinib for patients with myelofibrosis: 5-year update from the randomized, double-blind, placebo-controlled, phase 3 COMFORT-I trial. J Hematol Oncol. 2017;10:55.
  32. Blechman AB, Cabell CE, Weinberger CH, et al. Aggressive skin cancers occurring in patients treated with the Janus kinase inhibitor ruxolitinib. J Drugs Dermatol. 2017;16:508-511.
  33. Papp KA, Menter MA, Abe M, et al; OPT Pivotal 1 and OPT Pivotal 2 investigators. Tofacitinib, an oral Janus kinase inhibitor, for the treatment of chronic plaque psoriasis: results from two randomized, placebo-controlled, phase III trials. Br J Dermatol. 2015;173:949-961.
  34. Wellbrock C, Karasarides M, Marais R. The RAF proteins take centre stage. Nat Rev Mol Cell Biol. 2004;5:875-885.
  35. Gray-Schopfer V, Wellbrock C, Marais R. Melanoma biology and new targeted therapy. Nature. 2007;445:851-857.
  36. Arozarena I, Sanchez-Laorden B, Packer L, et al. Oncogenic BRAF induces melanoma cell invasion by downregulating the cGMP-specific phosphodiesterase PDE5A. Cancer Cell. 2011;19:45-57.
  37. Houslay MD. Hard times for oncogenic BRAF-expressing melanoma cells. Cancer Cell. 2011;19:3-4.
  38. Li WQ, Qureshi AA, Robinson KC, et al. Sildenafil use and increased risk of incident melanoma in US men: a prospective cohort study. JAMA Intern Med. 2014;174:964-970.
  39. Loeb S, Folkvaljon Y, Lambe M, et al. Use of phosphodiesterase type 5 inhibitors for erectile dysfunction and risk of malignant melanoma. JAMA. 2015;313:2449-2455.
  40. Lian Y, Yin H, Pollak MN, et al. Phosphodiesterase type 5 inhibitors and the risk of melanoma skin cancer. Eur Urol. 2016;70:808-815.
  41. Tang H, Wu W, Fu S, et al. Phosphodiesterase type 5 inhibitors and risk of melanoma: a meta-analysis. J Am Acad Dermatol. 2017;77:480.e9-488.e9.
Issue
Cutis - 104(4)
Issue
Cutis - 104(4)
Page Number
E32-E36
Page Number
E32-E36
Publications
MDedge Dermatology
Cutis
Publications
MDedge Dermatology
Cutis
Topics
Melanoma
Nonmelanoma Skin Cancer
Article Type
Article
Sections
Clinical Review
Inside the Article

Practice Points

  • Patients should be educated about the increased risk for skin malignancy while undergoing treatment with BRAF inhibitors, sonic hedgehog–inhibiting agents, Janus kinase (JAK) inhibitors, and phosphodiesterase 5 (PDE-5) inhibitors.
  • For BRAF inhibitors, sonic hedgehog–inhibiting agents, and JAK inhibitors, the increased risk for skin cancer warrants regular surveillance; however, given the indications for these medications, many patients will already be receiving regular skin screenings.
  • The association between PDE-5 inhibitors and melanoma as well as nonmelanoma skin cancer remains questionable, and increased skin surveillance is not recommended at this time, unless patients have other risk factors for cutaneous malignancy.
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