Synergism between radiation and other risk factors for breast cancer

Abstract

The question of whether the risk of radiation-induced breast cancer is additive or multiplicative (synergistic) with other risk factors for breast cancer has important implications for determining optimal guidelines for mammographic screening. Data from a follow-up study of 571 women given X-ray therapy for acute postpartum mastitis in Rochester, New York, and 993 control women were analyzed to examine this question. No synergism was found between breast irradiation and family history of breast cancer, late parity, oral contraceptive use, menopausal hormone use, or a composite of ovarian-related factors. Results indicated that women with a history of breast irradiation who develop benign breast disease, particularly cystic disease, are at high risk for breast cancer and should be carefully monitored. Women who were irradiated at the time of their first childbirth are also at especially high risk for breast cancer.