Technical Report No. 4-88
Risk of cancer among in utero children exposed to A-bomb radiation, 1950-84
Yoshimoto Y, Kato H, Schull WJEditor’s note: A publication based on this report was published in Lancet 2:665-9, 1988.
Summary
This study examines the risk of cancer (incidence) over a period of 40 years among the in utero exposed survivors of the atomic bombing of Hiroshima and Nagasaki, and adds eight years of follow-up to a previous report which was confined to mortality. Only two cases of childhood cancer were observed among these survivors in the first 14 years of life; both had been heavily exposed. Subsequent cancers have all been of the adult type. Not only did the observed cancers occur earlier in the greater than or equal to 0.30 Gy dose group than in the 0 Gy dose group but the incidence continues to increase and the crude cumulative incidence rate, 40 years after the A-bombing, is 3.9-fold greater in the greater than or equal to 0.30 Gy group. In the observation period 1950-84, based on the absorbed dose to the mother’s uterus, as estimated by the Dosimetry System 1986, the relative risk of cancer at 1 Gy is 3.77 with a 95% confidence interval of 1.14-13.48. For the entire greater than or equal to 0.01 Gy dose group the average excess risk per 104 person-year-gray is 6.57 (0.07-14.49) and the estimated attributable risk is 40.9% (2.9-90.2%). These results, when viewed in the perspective of fetus doses, suggest that susceptibility to radiation-induced cancers is higher in pre- than in postnatally exposed survivors (at least those exposed as adults). However, definitive conclusions must await further follow-up studies.
This study examines the risk of cancer (incidence) over a period of 40 years among the in utero exposed survivors of the atomic bombing of Hiroshima and Nagasaki, and adds eight years of follow-up to a previous report which was confined to mortality. Only two cases of childhood cancer were observed among these survivors in the first 14 years of life; both had been heavily exposed. Subsequent cancers have all been of the adult type. Not only did the observed cancers occur earlier in the greater than or equal to 0.30 Gy dose group than in the 0 Gy dose group but the incidence continues to increase and the crude cumulative incidence rate, 40 years after the A-bombing, is 3.9-fold greater in the greater than or equal to 0.30 Gy group. In the observation period 1950-84, based on the absorbed dose to the mother’s uterus, as estimated by the Dosimetry System 1986, the relative risk of cancer at 1 Gy is 3.77 with a 95% confidence interval of 1.14-13.48. For the entire greater than or equal to 0.01 Gy dose group the average excess risk per 104 person-year-gray is 6.57 (0.07-14.49) and the estimated attributable risk is 40.9% (2.9-90.2%). These results, when viewed in the perspective of fetus doses, suggest that susceptibility to radiation-induced cancers is higher in pre- than in postnatally exposed survivors (at least those exposed as adults). However, definitive conclusions must await further follow-up studies.