Oral Contraceptives and Post-menopausal Hormones and Risk of Contralateral Breast Cancer among BRCA1 and BRCA2 mutation carriers and non-carriers: The WECARE Study

摘要

The potential effects of oral contraceptive (OC) and post-menopausal hormone (PMH) use are not well understood among BRCA1 or BRCA2 deleterious mutation carriers with a history of breast cancer. In this study, we investigated the association between OC and PMH use and risk of contralateral breast cancer (CBC) in the WECARE (Women’s Environment, Cancer and Radiation Epidemiology) Study. The WECARE Study is a population-based case-control study of 705 women with asynchronous CBC and 1,398 women with unilateral breast cancer, including 181 BRCA1/2 mutation carriers. Risk factor information was assessed by telephone interview. Mutation status was measured using denaturing high-performance liquid chromatography followed by direct sequencing in all participants. Outcomes, treatment and tumor characteristics were abstracted from medical records. Ever use of OCs was not associated with risk among non-carriers (RR=0.87; 95% CI=0.66–1.15) or BRCA2 carriers (RR=0.82; 95% CI=0.21–3.13). BRCA1 carriers who used OCs had a non-significant greater risk than non-users (RR=2.38; 95% CI=0.72–7.83). Total duration of OC use and at least five years of use before age 30 were associated with a non-significant increased risk among mutation carriers, but not among non-carriers. Few women had ever used PMH and we found no significant associations between lifetime use and CBC risk among carriers and non-carriers. In conclusion, the association between OC/PMH use and risk of CBC does not differ significantly between carriers and non-carriers; however, because carriers have a higher baseline risk of second primaries even a potential small increase in risk as a result of OC use may be clinically relevant.