Thyroid cancer: epidemiological study of thyroid cancer in A-bomb survivors from extended life span study cohort in Hiroshima

We analysed thyroid cancers which were diagnosed clinically or detected at autopsy during 22 years (1958 to 1979) in a sample of 75,493 study subjects exposed in Hiroshima belonging to the extended LSS sample of the Radiation Effects Research Foundation. One hundred and twenty-five cases of clinical thyroid cancer (15 in males and 110 in females) were confirmed, giving a crude incidence rate per 100,000 person-years of 2.7 for males, 12.4 for females and 8.6 for both sexes combined. There was a significant increase of thyroid cancer with increase of atomic bomb radiation dose (thyroid tissue dose based on T65D) in females and in the sexes combined. This tendency was predominant in those exposed at less than 19 years of age. Compared to the control group, the relative risk in the greater than or equal to 0.50 Gy group was higher at 4.0 for males (not significant) and at 4.3 for females (p less than 0.01). Latent thyroid cancer was detected in 155 cases or 3.5% (2.5% for males and 4.5% for females) of the 4,425 cases that came to autopsy during the same period. Compared to the control group, the relative risk in the 50+ rad group was 1.7 for males (not significant), 2.0 for females (p less than 0.05) and 1.9 for both sexes combined (p less than 0.05). New data obtained from autopsy cases between 1950 and 1985 have been added.