Breast cancer risk after radiotherapy in infancy: A pooled analysis of twoSwedish cohorts of 17,202 infants

The incidence of breast cancer was studied in a cohort of 17,202 women irra diated for skin hemangioma in infancy at the Radiumhemmet, Stockholm, or th e Sahlgrenska University Hospital, Gothenburg. A major part of the cohort h ad been treated with radium-226 applicators, and the mean absorbed dose to the breasts was 0.29 Gy (range <0.0135.8 Gy). Two hundred forty-five breast cancers were diagnosed in the cohort during the period 1958-1.993, and the standardized incidence ratio (SIR) was 1.20 (95% CI 1.06-1.36). Different dose-response models were tested, and a linear model gave the best fit. Nei ther age at exposure, breast dose rate, ovarian dose nor time since exposur e had any statistically significant modifying effect, and breast dose was t he only determinant of risk. The excess relative risk per gray (ERR/GS') wa s 0.35 (95% CI 0.18-0.59), which is lower than in most other studies. (C) 1 999 by Radiation Research Society.