INCIDENCE OF PRIMARY MALIGNANCIES OTHER THAN BREAST-CANCER AMONG WOMEN TREATED WITH RADIATION-THERAPY FOR BENIGN BREAST DISEASE

This report presents data on the long-term risks of developing maligna ncies other than breast cancer after exposure to scattered doses of io nizing radiation. The estimates were based on a cohort of 3,090 women who were diagnosed clinically with benign breast disease between 1925 and 1961. A total of 1,216 women were treated with radiation therapy. The breasts received a mean absorbed dose of 5.84 Gy. Mean absorbed do ses owing to scatter to 14 other organs were also determined. The lung received the highest mean scattered dose (0.75 Gy; range 0.004-8.98 G y) and rectum the lowest (0.008 Gy; range 0-0.06 Gy). Median age at fi rst exposure was 40 years. The follow-up lasted up to 61 years after t reatment (mean follow-up 27 years). End-point data were obtained from population-based registers. With internal reference the relative risk for non-breast solid tumors was 1.2 (95% confidence interval 1.0-1.5). However, this excess was not apparent when comparison with the genera l population was made (standardized incidence ratio = 0.95; 95% confid ence interval 0.84-1.07). Among individual sites no significantly incr eased risks were observed. For stomach cancer there was a linear incre ase with dose (ERR/Gy = 1.3; two-sided P = 0.05). No increased risk wa s observed for leukemias. In two earlier reports, breast cancer incide nce has been shown to be significantly increased in this cohort of irr adiated women. Our results suggest that the scattered doses from the b reast irradiation may have increased the risk of cancers of other site s, but the small number of cases in different locations precludes stro ng interpretations. (C) 1997 by Radiation Research Society.