Multinational study of risk of breast cancer after ovarian cancer in women with a pathogenic or likely pathogenic BRCA1/2 variant

Female carriers of a pathogenic/likely pathogenic (P/LP) variant of BRCA1 or BRCA2 have high risks of developing both breast and ovarian/fallopian tube (‘ovarian’) cancers. Among BRCA carriers with ovarian cancer, it is not clear whether the risk of breast cancer is sufficiently high the risk-reducing bilateral mastectomy (RRBM) should be offered. A multinational study included 960 women with P/LP variant of BRCA1/2, a diagnosis of ovarian cancer, no other cancer histery, and no RRBM After a mean follow-up of 4.9 years, 41 of these women (4.3%) developed breast cancer, at a mean age of 57.5 years (range 39-74). Actuarial cumulative breast cancer risks after ovarian cancer were 4.4%, 8.9%, and 11.5% at 5, 10, and 15 year, respectively. Only three breast cancer-related deaths occurred. Among 741 age-matched BRCA carriers without ovarian cancer, actuarial cumulative risks of breast cancer were 20.9%, 38.6%, and 47.2% at 5, 10, and 15 years, respectively. The hazard ratio for breast cancer after overian cancer compared with no previous ovarian cancer diagnosis was 0.18 (p<0.0001). The authors conclude that after ovarian cancer, BRCA carriers have a relatively low risk of breast cancer. RRBM should not be recommended routinely; surveillance is a realistic alternative.