Atomic Bomb Survivors Still at Risk for Tumors

Nearly 60 years after exposure to radiation from the atomic bomb explosions in Hiroshima and Nagasaki, survivors remain at increased risk for both malignant and benign thyroid tumors, reported Dr. Misa Imaizumi of Nagasaki (Japan) University, and associates.

There is a significant, linear dose-response relationship: The prevalence of thyroid tumors rises as radiation dose increases. And the dose effects are significantly stronger in people who were exposed as children or adolescents in 1945 than they are in people who were 20 years old or older at that time.

These findings show that “careful examination of the thyroid is still important long after radiation exposure, especially for people exposed at younger ages,” Dr. Imaizumi and associates said (JAMA 2006;295:1011–22).

The researchers conducted what they described as the first comprehensive examinations for thyroid disease in 4,091 survivors of the Hiroshima and Nagasaki bombings. The 1,352 men and 2,739 women had a mean age of 70 years. About half had been within 2 kilometers of the hypocenters of the explosions.

Thyroid diseases were diagnosed at this examination or had been diagnosed previously in 1,833 subjects (44.8%). The prevalence of thyroid disease was significantly higher in women (51.0%) than in men (32.2%).

Malignant thyroid tumors were found in 87 subjects (2.1%), and benign nodules were detected in 207 subjects (5.1%). Another 71 subjects had previously had malignant tumors removed, whereas 43 had previously had benign nodules removed. Thyroid cysts were noted in an additional 324 subjects (7.9%), whereas 589 (14.4%) had mixed-type solid nodules and 321 (7.8%) had nodules for which cytology results were unavailable.

For all of these lesions, the prevalence increased in direct proportion to the degree of radiation exposure. Moreover, the prevalence was highest in people who had been exposed to the atomic bombs' radiation as children or adolescents. The exact reason for this is unknown, but it is likely that children's organs are more sensitive to radiation because of their higher rates of cell proliferation associated with growth, the investigators said.

Autoimmune thyroid diseases were not associated with radiation dose. A total of 1,127 subjects (27.5%) had antithyroid antibodies, 230 (5.6%) had hypothyroidism, and 62 (1.5%) had hyperthyroidism.

In an editorial comment, John D. Boice Jr., Sc.D., of Vanderbilt University in Nashville, Tenn. said, “It is remarkable that a biological effect from a single brief environmental exposure nearly 60 years in the past is still present and can be detected.”

The findings of Dr. Imaizumi and associates show that after radiation exposure, the risk of both malignant and benign thyroid disease “apparently lasts for life,” Dr. Boice said (JAMA 2006;295:1060–2).

Nearly 60 years after exposure to radiation from the atomic bomb explosions in Hiroshima and Nagasaki, survivors remain at increased risk for both malignant and benign thyroid tumors, reported Dr. Misa Imaizumi of Nagasaki (Japan) University, and associates.

There is a significant, linear dose-response relationship: The prevalence of thyroid tumors rises as radiation dose increases. And the dose effects are significantly stronger in people who were exposed as children or adolescents in 1945 than they are in people who were 20 years old or older at that time.

These findings show that “careful examination of the thyroid is still important long after radiation exposure, especially for people exposed at younger ages,” Dr. Imaizumi and associates said (JAMA 2006;295:1011–22).

The researchers conducted what they described as the first comprehensive examinations for thyroid disease in 4,091 survivors of the Hiroshima and Nagasaki bombings. The 1,352 men and 2,739 women had a mean age of 70 years. About half had been within 2 kilometers of the hypocenters of the explosions.

Thyroid diseases were diagnosed at this examination or had been diagnosed previously in 1,833 subjects (44.8%). The prevalence of thyroid disease was significantly higher in women (51.0%) than in men (32.2%).

Malignant thyroid tumors were found in 87 subjects (2.1%), and benign nodules were detected in 207 subjects (5.1%). Another 71 subjects had previously had malignant tumors removed, whereas 43 had previously had benign nodules removed. Thyroid cysts were noted in an additional 324 subjects (7.9%), whereas 589 (14.4%) had mixed-type solid nodules and 321 (7.8%) had nodules for which cytology results were unavailable.

For all of these lesions, the prevalence increased in direct proportion to the degree of radiation exposure. Moreover, the prevalence was highest in people who had been exposed to the atomic bombs' radiation as children or adolescents. The exact reason for this is unknown, but it is likely that children's organs are more sensitive to radiation because of their higher rates of cell proliferation associated with growth, the investigators said.

Autoimmune thyroid diseases were not associated with radiation dose. A total of 1,127 subjects (27.5%) had antithyroid antibodies, 230 (5.6%) had hypothyroidism, and 62 (1.5%) had hyperthyroidism.

In an editorial comment, John D. Boice Jr., Sc.D., of Vanderbilt University in Nashville, Tenn. said, “It is remarkable that a biological effect from a single brief environmental exposure nearly 60 years in the past is still present and can be detected.”

The findings of Dr. Imaizumi and associates show that after radiation exposure, the risk of both malignant and benign thyroid disease “apparently lasts for life,” Dr. Boice said (JAMA 2006;295:1060–2).

Nearly 60 years after exposure to radiation from the atomic bomb explosions in Hiroshima and Nagasaki, survivors remain at increased risk for both malignant and benign thyroid tumors, reported Dr. Misa Imaizumi of Nagasaki (Japan) University, and associates.

There is a significant, linear dose-response relationship: The prevalence of thyroid tumors rises as radiation dose increases. And the dose effects are significantly stronger in people who were exposed as children or adolescents in 1945 than they are in people who were 20 years old or older at that time.

These findings show that “careful examination of the thyroid is still important long after radiation exposure, especially for people exposed at younger ages,” Dr. Imaizumi and associates said (JAMA 2006;295:1011–22).

The researchers conducted what they described as the first comprehensive examinations for thyroid disease in 4,091 survivors of the Hiroshima and Nagasaki bombings. The 1,352 men and 2,739 women had a mean age of 70 years. About half had been within 2 kilometers of the hypocenters of the explosions.

Thyroid diseases were diagnosed at this examination or had been diagnosed previously in 1,833 subjects (44.8%). The prevalence of thyroid disease was significantly higher in women (51.0%) than in men (32.2%).

Malignant thyroid tumors were found in 87 subjects (2.1%), and benign nodules were detected in 207 subjects (5.1%). Another 71 subjects had previously had malignant tumors removed, whereas 43 had previously had benign nodules removed. Thyroid cysts were noted in an additional 324 subjects (7.9%), whereas 589 (14.4%) had mixed-type solid nodules and 321 (7.8%) had nodules for which cytology results were unavailable.

For all of these lesions, the prevalence increased in direct proportion to the degree of radiation exposure. Moreover, the prevalence was highest in people who had been exposed to the atomic bombs' radiation as children or adolescents. The exact reason for this is unknown, but it is likely that children's organs are more sensitive to radiation because of their higher rates of cell proliferation associated with growth, the investigators said.

Autoimmune thyroid diseases were not associated with radiation dose. A total of 1,127 subjects (27.5%) had antithyroid antibodies, 230 (5.6%) had hypothyroidism, and 62 (1.5%) had hyperthyroidism.

In an editorial comment, John D. Boice Jr., Sc.D., of Vanderbilt University in Nashville, Tenn. said, “It is remarkable that a biological effect from a single brief environmental exposure nearly 60 years in the past is still present and can be detected.”

The findings of Dr. Imaizumi and associates show that after radiation exposure, the risk of both malignant and benign thyroid disease “apparently lasts for life,” Dr. Boice said (JAMA 2006;295:1060–2).