In favorable intermediate-risk prostate cancer, brachytherapy alone suffices

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– In a finding hailed as “paradigm changing,” men with favorable intermediate-risk prostate cancer may have good disease control with brachytherapy alone, with fewer late-term toxicities than with brachytherapy combined with external-beam radiation, investigators reported.

After 5 years of follow-up, there were no significant differences in rates of freedom from disease progression among patients assigned to receive combined external-beam radiation (EBRT) and transperineal interstitial permanent brachytherapy (PB) or PB alone in selected patients with intermediate-risk prostatic carcinoma.

ASTRO
Dr. Bradley R. Prestidge
There were no differences in acute toxicities between the treatment groups, but patients who underwent combined therapy had significantly more late grade 2 or grade 3 toxicities than those who underwent brachytherapy alone, reported Bradley R. Prestidge, MD, medical director of the Bon Secours Cancer Institute at DePaul Medical Center in Norfolk, Virginia.

“I think you’re underselling your results – I’m pretty excited about these results,” Colleen Lawton, MD, professor and vice chair of radiation oncology at the Medical College of Wisconsin in Milwaukee, told Dr. Prestidge at the annual meeting of the American Society of Radiation Oncology.

The results show that, “for the intermediate-risk group, not the worst of intermediate [risk] but the vast majority, they don’t need the toxicity of that external beam, and they don’t need the cost of it,” she said at a briefing following his presentation of the data in a plenary session.

Dr. Lawton said that, when the NRG Oncology/RTOG 0232study was initiated (the first patients were enrolled in 2003), “there were factions that believed you could not treat intermediate-risk prostate cancer – which isn’t the best, isn’t the worse, but is somewhere in the middle – with anything but the combination, and this shows that’s not true.”

The trial was designed to test the hypothesis that patients with intermediate-risk prostate cancer treated with combined EBRT and PB would have a 10% improvement in freedom from progression (FFP), compared with men treated with PB alone.

A total of 579 patients with histologically confirmed prostate cancer, stages T1c-2b and Zubrod performance score 0 or 1 were enrolled. The patients also had Gleason score 2-6 and prostate-specific antigen (PSA) from 10 to less than 20 ng/mL; Gleason score and PSA less than 10 ng/mL; or prostate volume less than 60 cc.

In addition, androgen deprivation therapy (ADT) was not allowed on the study, and patients could not have distant metastases or radiographically suspicious nodes at the time of enrollment.

Patients were stratified by stage, Gleason score, PSA and history of ADT, and then randomized to the combined therapy, consisting of 45 Gy in a partial pelvis dose delivered in 1.8 Gy fractions for 5 weeks, followed 2-4 weeks later with brachytherapy using either a radioactive iodine (I-125) source prescribed as a 110-Gy boost dose, or palladium 103 in a 100 Gy boost dose; or brachytherapy alone (145-Gy dose with I-I25, 125-Gy dose with palladium 103). EBRT was delivered by either intensity-modulated radiation (43%) or 3D conformal radiation.

Five years after randomization, there were a total of 66 cases of treatment failure (measured as either biochemical failure according to ASTRO criteria, local progression, distant metastases, or death from any cause), 34 occurring in men treated with the combination, and 32 in men treated with brachytherapy alone. Biochemical failures accounted for 68% of events among patients on the combined modalities and 53% of those on brachytherapy alone. There were 9 deaths in the combined arm and 14 deaths in the brachytherapy-only arm, but none were prostate cancer related, Dr. Prestidge said.

In multivariate analysis adjusted for treatment type, age, race, prior hormonal therapy, Gleason/PSA, and tumor stage, the only significant predictor of FFP was Gleason 7/PSA less than 10 ng/mL, which was associated with better outcomes, compared with Gleason score less than 7/PSA 10-20 ng/mL (odds ratio, 0.5; P = .046).

There was no difference in 5-year overall survival between the groups.

As noted before, there were no significant differences in acute toxicities, but there were significantly more late grade 2 or greater toxicities among patients who underwent EBRT and PB (53% vs. 37%; P less than .0001), and more late grade 3 or greater toxicities (12% vs. 7%; P = .039).

Michael J Zelefsky, MD, professor of radiation oncology and chief of the brachytherapy service at Memorial Sloan Kettering Cancer Center in New York, the invited discussant, said that the study suggests that “combining EBRT with brachytherapy for favorable intermediate-risk disease may constitute unnecessary overkill.”

He asserted, however, that favorable intermediate-risk disease behaves clinically more like low-risk disease, whereas unfavorable intermediate-risk disease is closer to high-risk disease in its clinical behavior.

It is plausible that, for patients with unfavorable intermediate-risk disease, added dose intensification associated with combined modality therapy could result in improved FFP and local tumor control, he said.

The study was funded by the National Cancer Institute. Dr. Prestidge disclosed consulting for Varian, Elekta, and IsoRay. Dr. Zelefsky disclosed receiving honoraria from Bebig Brachytherapy, Augmenix, and as editor-in-chief of Brachytherapy. Dr. Lawton reported no relevant disclosures.

 

 

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– In a finding hailed as “paradigm changing,” men with favorable intermediate-risk prostate cancer may have good disease control with brachytherapy alone, with fewer late-term toxicities than with brachytherapy combined with external-beam radiation, investigators reported.

After 5 years of follow-up, there were no significant differences in rates of freedom from disease progression among patients assigned to receive combined external-beam radiation (EBRT) and transperineal interstitial permanent brachytherapy (PB) or PB alone in selected patients with intermediate-risk prostatic carcinoma.

ASTRO
Dr. Bradley R. Prestidge
There were no differences in acute toxicities between the treatment groups, but patients who underwent combined therapy had significantly more late grade 2 or grade 3 toxicities than those who underwent brachytherapy alone, reported Bradley R. Prestidge, MD, medical director of the Bon Secours Cancer Institute at DePaul Medical Center in Norfolk, Virginia.

“I think you’re underselling your results – I’m pretty excited about these results,” Colleen Lawton, MD, professor and vice chair of radiation oncology at the Medical College of Wisconsin in Milwaukee, told Dr. Prestidge at the annual meeting of the American Society of Radiation Oncology.

The results show that, “for the intermediate-risk group, not the worst of intermediate [risk] but the vast majority, they don’t need the toxicity of that external beam, and they don’t need the cost of it,” she said at a briefing following his presentation of the data in a plenary session.

Dr. Lawton said that, when the NRG Oncology/RTOG 0232study was initiated (the first patients were enrolled in 2003), “there were factions that believed you could not treat intermediate-risk prostate cancer – which isn’t the best, isn’t the worse, but is somewhere in the middle – with anything but the combination, and this shows that’s not true.”

The trial was designed to test the hypothesis that patients with intermediate-risk prostate cancer treated with combined EBRT and PB would have a 10% improvement in freedom from progression (FFP), compared with men treated with PB alone.

A total of 579 patients with histologically confirmed prostate cancer, stages T1c-2b and Zubrod performance score 0 or 1 were enrolled. The patients also had Gleason score 2-6 and prostate-specific antigen (PSA) from 10 to less than 20 ng/mL; Gleason score and PSA less than 10 ng/mL; or prostate volume less than 60 cc.

In addition, androgen deprivation therapy (ADT) was not allowed on the study, and patients could not have distant metastases or radiographically suspicious nodes at the time of enrollment.

Patients were stratified by stage, Gleason score, PSA and history of ADT, and then randomized to the combined therapy, consisting of 45 Gy in a partial pelvis dose delivered in 1.8 Gy fractions for 5 weeks, followed 2-4 weeks later with brachytherapy using either a radioactive iodine (I-125) source prescribed as a 110-Gy boost dose, or palladium 103 in a 100 Gy boost dose; or brachytherapy alone (145-Gy dose with I-I25, 125-Gy dose with palladium 103). EBRT was delivered by either intensity-modulated radiation (43%) or 3D conformal radiation.

Five years after randomization, there were a total of 66 cases of treatment failure (measured as either biochemical failure according to ASTRO criteria, local progression, distant metastases, or death from any cause), 34 occurring in men treated with the combination, and 32 in men treated with brachytherapy alone. Biochemical failures accounted for 68% of events among patients on the combined modalities and 53% of those on brachytherapy alone. There were 9 deaths in the combined arm and 14 deaths in the brachytherapy-only arm, but none were prostate cancer related, Dr. Prestidge said.

In multivariate analysis adjusted for treatment type, age, race, prior hormonal therapy, Gleason/PSA, and tumor stage, the only significant predictor of FFP was Gleason 7/PSA less than 10 ng/mL, which was associated with better outcomes, compared with Gleason score less than 7/PSA 10-20 ng/mL (odds ratio, 0.5; P = .046).

There was no difference in 5-year overall survival between the groups.

As noted before, there were no significant differences in acute toxicities, but there were significantly more late grade 2 or greater toxicities among patients who underwent EBRT and PB (53% vs. 37%; P less than .0001), and more late grade 3 or greater toxicities (12% vs. 7%; P = .039).

Michael J Zelefsky, MD, professor of radiation oncology and chief of the brachytherapy service at Memorial Sloan Kettering Cancer Center in New York, the invited discussant, said that the study suggests that “combining EBRT with brachytherapy for favorable intermediate-risk disease may constitute unnecessary overkill.”

He asserted, however, that favorable intermediate-risk disease behaves clinically more like low-risk disease, whereas unfavorable intermediate-risk disease is closer to high-risk disease in its clinical behavior.

It is plausible that, for patients with unfavorable intermediate-risk disease, added dose intensification associated with combined modality therapy could result in improved FFP and local tumor control, he said.

The study was funded by the National Cancer Institute. Dr. Prestidge disclosed consulting for Varian, Elekta, and IsoRay. Dr. Zelefsky disclosed receiving honoraria from Bebig Brachytherapy, Augmenix, and as editor-in-chief of Brachytherapy. Dr. Lawton reported no relevant disclosures.

 

 

 

– In a finding hailed as “paradigm changing,” men with favorable intermediate-risk prostate cancer may have good disease control with brachytherapy alone, with fewer late-term toxicities than with brachytherapy combined with external-beam radiation, investigators reported.

After 5 years of follow-up, there were no significant differences in rates of freedom from disease progression among patients assigned to receive combined external-beam radiation (EBRT) and transperineal interstitial permanent brachytherapy (PB) or PB alone in selected patients with intermediate-risk prostatic carcinoma.

ASTRO
Dr. Bradley R. Prestidge
There were no differences in acute toxicities between the treatment groups, but patients who underwent combined therapy had significantly more late grade 2 or grade 3 toxicities than those who underwent brachytherapy alone, reported Bradley R. Prestidge, MD, medical director of the Bon Secours Cancer Institute at DePaul Medical Center in Norfolk, Virginia.

“I think you’re underselling your results – I’m pretty excited about these results,” Colleen Lawton, MD, professor and vice chair of radiation oncology at the Medical College of Wisconsin in Milwaukee, told Dr. Prestidge at the annual meeting of the American Society of Radiation Oncology.

The results show that, “for the intermediate-risk group, not the worst of intermediate [risk] but the vast majority, they don’t need the toxicity of that external beam, and they don’t need the cost of it,” she said at a briefing following his presentation of the data in a plenary session.

Dr. Lawton said that, when the NRG Oncology/RTOG 0232study was initiated (the first patients were enrolled in 2003), “there were factions that believed you could not treat intermediate-risk prostate cancer – which isn’t the best, isn’t the worse, but is somewhere in the middle – with anything but the combination, and this shows that’s not true.”

The trial was designed to test the hypothesis that patients with intermediate-risk prostate cancer treated with combined EBRT and PB would have a 10% improvement in freedom from progression (FFP), compared with men treated with PB alone.

A total of 579 patients with histologically confirmed prostate cancer, stages T1c-2b and Zubrod performance score 0 or 1 were enrolled. The patients also had Gleason score 2-6 and prostate-specific antigen (PSA) from 10 to less than 20 ng/mL; Gleason score and PSA less than 10 ng/mL; or prostate volume less than 60 cc.

In addition, androgen deprivation therapy (ADT) was not allowed on the study, and patients could not have distant metastases or radiographically suspicious nodes at the time of enrollment.

Patients were stratified by stage, Gleason score, PSA and history of ADT, and then randomized to the combined therapy, consisting of 45 Gy in a partial pelvis dose delivered in 1.8 Gy fractions for 5 weeks, followed 2-4 weeks later with brachytherapy using either a radioactive iodine (I-125) source prescribed as a 110-Gy boost dose, or palladium 103 in a 100 Gy boost dose; or brachytherapy alone (145-Gy dose with I-I25, 125-Gy dose with palladium 103). EBRT was delivered by either intensity-modulated radiation (43%) or 3D conformal radiation.

Five years after randomization, there were a total of 66 cases of treatment failure (measured as either biochemical failure according to ASTRO criteria, local progression, distant metastases, or death from any cause), 34 occurring in men treated with the combination, and 32 in men treated with brachytherapy alone. Biochemical failures accounted for 68% of events among patients on the combined modalities and 53% of those on brachytherapy alone. There were 9 deaths in the combined arm and 14 deaths in the brachytherapy-only arm, but none were prostate cancer related, Dr. Prestidge said.

In multivariate analysis adjusted for treatment type, age, race, prior hormonal therapy, Gleason/PSA, and tumor stage, the only significant predictor of FFP was Gleason 7/PSA less than 10 ng/mL, which was associated with better outcomes, compared with Gleason score less than 7/PSA 10-20 ng/mL (odds ratio, 0.5; P = .046).

There was no difference in 5-year overall survival between the groups.

As noted before, there were no significant differences in acute toxicities, but there were significantly more late grade 2 or greater toxicities among patients who underwent EBRT and PB (53% vs. 37%; P less than .0001), and more late grade 3 or greater toxicities (12% vs. 7%; P = .039).

Michael J Zelefsky, MD, professor of radiation oncology and chief of the brachytherapy service at Memorial Sloan Kettering Cancer Center in New York, the invited discussant, said that the study suggests that “combining EBRT with brachytherapy for favorable intermediate-risk disease may constitute unnecessary overkill.”

He asserted, however, that favorable intermediate-risk disease behaves clinically more like low-risk disease, whereas unfavorable intermediate-risk disease is closer to high-risk disease in its clinical behavior.

It is plausible that, for patients with unfavorable intermediate-risk disease, added dose intensification associated with combined modality therapy could result in improved FFP and local tumor control, he said.

The study was funded by the National Cancer Institute. Dr. Prestidge disclosed consulting for Varian, Elekta, and IsoRay. Dr. Zelefsky disclosed receiving honoraria from Bebig Brachytherapy, Augmenix, and as editor-in-chief of Brachytherapy. Dr. Lawton reported no relevant disclosures.

 

 

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Key clinical point: It may be clinically unnecessary to add external-beam radiation to brachytherapy in men with favorable intermediate-risk prostate cancer.

Major finding: Outcomes were comparable for men with favorable intermediate-risk prostate cancer treated with external-beam radiation plus brachytherapy or brachytherapy alone.

Data source: Randomized, controlled trial in 579 men with intermediate-risk prostate cancer.

Disclosures: The study was funded by the National Cancer Institute. Dr. Prestidge disclosed consulting for Varian, Elekta, and IsoRay. Dr. Zelefsky disclosed receiving honoraria from Bebig Brachytherapy, Augmenix, and as editor-in-chief of Brachytherapy. Dr. Lawton reported no relevant disclosures.

Newer Radiotherapy for Prostate Cancer Less Harmful to Rectum

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Newer Radiotherapy for Prostate Cancer Less Harmful to Rectum

Men with localized prostate cancer had fewer acute and late side effects in the bowel and rectum when they were treated with a newer, more targeted form of radiotherapy in a phase III dose-escalation trial conducted by the Radiation Therapy Oncology Group.

The newer procedure, intensity-modulated radiation therapy (IMRT), was associated with 26% fewer late rectal and bowel toxicities, compared with three-dimensional conformal radiation therapy (3D-CRT) in an analysis of men with localized prostate cancer who were part of the study’s high-dose treatment arm.

Although the difference in late toxicity was not statistically significant, acute grade 2 or higher rectal, bowel, and bladder toxicities were significantly fewer, and radiation doses to the bladder and rectum were significantly reduced as well.

Patients in the RTOG 0126 trial were initially treated with 3D-CRT, but the trial protocol was amended after 1 year to allow IMRT, which is a newer, specialized form of 3D-CRT that allows more precise delivery of radiation to the tumor.

The current study represents a preliminary analysis of acute and late toxicities in 491 patients treated with 3D-CRT and 257 patients treated with IMRT. The findings will be presented on Oct. 3 at the annual meeting of the American Society for Radiation Oncology (ASTRO).

Acute grade 2 toxicities occurred in 16.9% in the 3D-CRT arm and 13.9% of patients in the IMRT groups. Acute grade 3 toxicities occurred in 2.5% and 2.4% of patients in the groups, respectively, Dr. Jeff Michalski reported during a press conference held in advance of the ASTRO meeting.

No acute grade 4 toxicities occurred in the 3D-CRT group, but 0.4% of patients in the IMRT group experienced grade 4 toxicities, according to Dr. Michalski, professor and vice chair of radiation oncology at Washington University Medical Center in St. Louis.

Univariate and multivariate analyses demonstrated a significant decrease in acute collective genitourinary and gastrointestinal toxicity for IMRT, but there were no significant differences for acute grade 2 or higher genitourinary toxicities alone, he noted.

As for late toxicities – which are particularly important to control because they can be irreversible – 23.6% and 19.9% of patients in the 3D-CRT and IMRT groups, respectively, experienced grade 2 toxicities; 8.9% and 4.7%, respectively, experienced grade 3 toxicities; 0.4% of patients in both groups experienced grade 4 toxicities, Dr. Michalski said. Although 0.2% of the 3D-CRT group had a late grade 5 toxicity, none was reported in men receiving IMRT.

The difference between 3D-CRT and IMRT in late toxicities did not reach statistical significance, but there was a trend toward a "clinically meaningful" 26% reduction in grade 2 or higher late toxicities with IMRT, he said.

Notably, there was a significant 15% increase in grade 2 or higher rectal toxicity in white men vs. men of other races, regardless of treatment type. The causes of this finding are unclear, but may be associated with differences in treatment tolerance or cultural differences in the reporting of side effects, he suggested.

"IMRT is a safe and very well-tolerated therapy associated with many fewer acute and late complications than 3D-CRT," Dr. Michalski said, adding, "I believe this study supports the use of IMRT in the management of localized prostate cancer."

Although prior findings have supported the notion of a technical advantage with IMRT in terms of delivering a higher dose of radiation to the tumor without increasing toxicity to the bladder and rectum, a good data set allowing direct comparisons of 3D-CRT and IMRT was lacking, he said.

"This is the first contemporary group of patients that demonstrates a benefit," he said.

This study was supported the ASTRO Radiation Oncology Institute and by several grants from the National Cancer Institute. Dr. Michalski reported receiving funding from Augmenix, Elekta, and Viewray.

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Men with localized prostate cancer had fewer acute and late side effects in the bowel and rectum when they were treated with a newer, more targeted form of radiotherapy in a phase III dose-escalation trial conducted by the Radiation Therapy Oncology Group.

The newer procedure, intensity-modulated radiation therapy (IMRT), was associated with 26% fewer late rectal and bowel toxicities, compared with three-dimensional conformal radiation therapy (3D-CRT) in an analysis of men with localized prostate cancer who were part of the study’s high-dose treatment arm.

Although the difference in late toxicity was not statistically significant, acute grade 2 or higher rectal, bowel, and bladder toxicities were significantly fewer, and radiation doses to the bladder and rectum were significantly reduced as well.

Patients in the RTOG 0126 trial were initially treated with 3D-CRT, but the trial protocol was amended after 1 year to allow IMRT, which is a newer, specialized form of 3D-CRT that allows more precise delivery of radiation to the tumor.

The current study represents a preliminary analysis of acute and late toxicities in 491 patients treated with 3D-CRT and 257 patients treated with IMRT. The findings will be presented on Oct. 3 at the annual meeting of the American Society for Radiation Oncology (ASTRO).

Acute grade 2 toxicities occurred in 16.9% in the 3D-CRT arm and 13.9% of patients in the IMRT groups. Acute grade 3 toxicities occurred in 2.5% and 2.4% of patients in the groups, respectively, Dr. Jeff Michalski reported during a press conference held in advance of the ASTRO meeting.

No acute grade 4 toxicities occurred in the 3D-CRT group, but 0.4% of patients in the IMRT group experienced grade 4 toxicities, according to Dr. Michalski, professor and vice chair of radiation oncology at Washington University Medical Center in St. Louis.

Univariate and multivariate analyses demonstrated a significant decrease in acute collective genitourinary and gastrointestinal toxicity for IMRT, but there were no significant differences for acute grade 2 or higher genitourinary toxicities alone, he noted.

As for late toxicities – which are particularly important to control because they can be irreversible – 23.6% and 19.9% of patients in the 3D-CRT and IMRT groups, respectively, experienced grade 2 toxicities; 8.9% and 4.7%, respectively, experienced grade 3 toxicities; 0.4% of patients in both groups experienced grade 4 toxicities, Dr. Michalski said. Although 0.2% of the 3D-CRT group had a late grade 5 toxicity, none was reported in men receiving IMRT.

The difference between 3D-CRT and IMRT in late toxicities did not reach statistical significance, but there was a trend toward a "clinically meaningful" 26% reduction in grade 2 or higher late toxicities with IMRT, he said.

Notably, there was a significant 15% increase in grade 2 or higher rectal toxicity in white men vs. men of other races, regardless of treatment type. The causes of this finding are unclear, but may be associated with differences in treatment tolerance or cultural differences in the reporting of side effects, he suggested.

"IMRT is a safe and very well-tolerated therapy associated with many fewer acute and late complications than 3D-CRT," Dr. Michalski said, adding, "I believe this study supports the use of IMRT in the management of localized prostate cancer."

Although prior findings have supported the notion of a technical advantage with IMRT in terms of delivering a higher dose of radiation to the tumor without increasing toxicity to the bladder and rectum, a good data set allowing direct comparisons of 3D-CRT and IMRT was lacking, he said.

"This is the first contemporary group of patients that demonstrates a benefit," he said.

This study was supported the ASTRO Radiation Oncology Institute and by several grants from the National Cancer Institute. Dr. Michalski reported receiving funding from Augmenix, Elekta, and Viewray.

Men with localized prostate cancer had fewer acute and late side effects in the bowel and rectum when they were treated with a newer, more targeted form of radiotherapy in a phase III dose-escalation trial conducted by the Radiation Therapy Oncology Group.

The newer procedure, intensity-modulated radiation therapy (IMRT), was associated with 26% fewer late rectal and bowel toxicities, compared with three-dimensional conformal radiation therapy (3D-CRT) in an analysis of men with localized prostate cancer who were part of the study’s high-dose treatment arm.

Although the difference in late toxicity was not statistically significant, acute grade 2 or higher rectal, bowel, and bladder toxicities were significantly fewer, and radiation doses to the bladder and rectum were significantly reduced as well.

Patients in the RTOG 0126 trial were initially treated with 3D-CRT, but the trial protocol was amended after 1 year to allow IMRT, which is a newer, specialized form of 3D-CRT that allows more precise delivery of radiation to the tumor.

The current study represents a preliminary analysis of acute and late toxicities in 491 patients treated with 3D-CRT and 257 patients treated with IMRT. The findings will be presented on Oct. 3 at the annual meeting of the American Society for Radiation Oncology (ASTRO).

Acute grade 2 toxicities occurred in 16.9% in the 3D-CRT arm and 13.9% of patients in the IMRT groups. Acute grade 3 toxicities occurred in 2.5% and 2.4% of patients in the groups, respectively, Dr. Jeff Michalski reported during a press conference held in advance of the ASTRO meeting.

No acute grade 4 toxicities occurred in the 3D-CRT group, but 0.4% of patients in the IMRT group experienced grade 4 toxicities, according to Dr. Michalski, professor and vice chair of radiation oncology at Washington University Medical Center in St. Louis.

Univariate and multivariate analyses demonstrated a significant decrease in acute collective genitourinary and gastrointestinal toxicity for IMRT, but there were no significant differences for acute grade 2 or higher genitourinary toxicities alone, he noted.

As for late toxicities – which are particularly important to control because they can be irreversible – 23.6% and 19.9% of patients in the 3D-CRT and IMRT groups, respectively, experienced grade 2 toxicities; 8.9% and 4.7%, respectively, experienced grade 3 toxicities; 0.4% of patients in both groups experienced grade 4 toxicities, Dr. Michalski said. Although 0.2% of the 3D-CRT group had a late grade 5 toxicity, none was reported in men receiving IMRT.

The difference between 3D-CRT and IMRT in late toxicities did not reach statistical significance, but there was a trend toward a "clinically meaningful" 26% reduction in grade 2 or higher late toxicities with IMRT, he said.

Notably, there was a significant 15% increase in grade 2 or higher rectal toxicity in white men vs. men of other races, regardless of treatment type. The causes of this finding are unclear, but may be associated with differences in treatment tolerance or cultural differences in the reporting of side effects, he suggested.

"IMRT is a safe and very well-tolerated therapy associated with many fewer acute and late complications than 3D-CRT," Dr. Michalski said, adding, "I believe this study supports the use of IMRT in the management of localized prostate cancer."

Although prior findings have supported the notion of a technical advantage with IMRT in terms of delivering a higher dose of radiation to the tumor without increasing toxicity to the bladder and rectum, a good data set allowing direct comparisons of 3D-CRT and IMRT was lacking, he said.

"This is the first contemporary group of patients that demonstrates a benefit," he said.

This study was supported the ASTRO Radiation Oncology Institute and by several grants from the National Cancer Institute. Dr. Michalski reported receiving funding from Augmenix, Elekta, and Viewray.

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Major Finding: Acute grade 2 toxicities occurred in 16.9% and 13.9% of patients in the 3D-CRT and IMRT groups, respectively.

Data Source: An analysis of data on 748 men with localized prostate cancer treated with high-dose radiation in a phase III dose-escalation trial.

Disclosures: This study was supported the ASTRO Radiation Oncology Institute and by several grants from the National Cancer Institute. Dr. Michalski reported receiving funding from Augmenix, Elekta, and Viewray.