Risk of solid tumors after irradiation in infancy.

Cancer incidence was studied in 14,351 subjects exposed to ionizing radiation for skin hemangioma at the Radiumhemmet, 1920-1959. Record-linkage was done with the Swedish Cancer Registry for the period 1958-1986. After a mean follow-up of 39 years, 300 cancers were observed and the standardized incidence ratio (SIR) was 1.11 (95% confidence interval (CI) 0.99-1.24). The absorbed dose to different organs varied from < 0.01 Gy to > 40 Gy. The thyroid cancer incidence was significantly increased (SIR = 2.28; 95% CI 1.33-3.65) and for cancer of the breast SIR was 1.24 (95% CI 0.98-1.54). Regarding pancreatic cancer and tumors of the endocrine glands the statistically significantly increased SIRs were based on a small number of cases and might therefore only be a coincidence. No confirmed increased incidence could be established for other cancer sites.