Mammography screening and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers: a prospective study.

Women with a genetic predisposition to breast cancer may be at increased risk of cancer after exposure to ionizing radiation. It is unclear whether mammography screening increases the risk of breast cancer among BRCA1 and BRCA2 carriers. We identified 2,346 women with a BRCA1 (n = 1844) or BRCA2 (n = 502) mutation and no breast cancer, and we reviewed their history of mammography exposure. These women were followed for an average of 5.3 years and were observed for new breast cancer diagnoses. At study entry, 1808 women (77.1 %) reported ever having had a mammogram; of these, 204 women (11.2 %) reported having had a mammogram before age 30. We estimated the hazard ratios for the development of invasive breast cancer, conditional on the number of prior mammograms and on the age at first mammogram. Hazard ratios were estimated and stratified by gene (BRCA1 or BRCA2), relative to women with no exposure. We observed no significant association between prior mammography exposure and breast cancer risk for BRCA1 carriers (HR 0.79; 95 % CI 0.53-1.19; P = 0.26) or for BRCA2 carriers (HR 0.90; 95 % CI 0.35-2.34; P = 0.83). An early age at first mammogram (<30 years) did not increase breast cancer risk among BRCA1 carriers (HR 0.75; 95 % CI 0.41-1.37; P = 0.35) or among BRCA2 carriers (HR 0.69; 95 % CI 0.19-2.48; P = 0.57). Exposure to mammography in women with BRCA1 and BRCA2 mutations is not associated with an increased risk of breast cancer.