Women with a BRCA1 or BRCA2 mutation have an elevated risk of
breast cancer and of contralateral
breast cancer. In this study, we estimate the risk of non-synchronous ipsilateral
breast cancer after a diagnosis of
breast cancer in BRCA carriers and evaluate the effects of various treatments on this risk. Patients were 396 women with stage I or stage II
breast cancer with an intact ipsilateral breast and for whom a BRCA1 or BRCA2 mutation had been identified in the family. Patients were followed from the initial diagnosis of
cancer until the first of ipsilateral
mastectomy, ipsilateral
breast cancer, death or last follow-up. The 5-year actuarial risk of ipsilateral
breast cancer was 5.8% (95% CI 3.2-8.4%) and the 10-year risk was 12.9% (95% CI 8.7-17.1%). Subjects who received
chemotherapy had a significantly lower risk of ipsilateral
breast cancer compared to those who did not receive
chemotherapy (RR 0.45; 95% CI 0.24-0.84; P = 0.01).
Radiotherapy was associated with a reduced risk of ipsilateral
breast cancer (RR 0.28; 95% CI 0.12-0.63; P = 0.002).
Oophorectomy was associated with a significant reduction in the risk of ipsilateral
breast cancer (RR 0.33; 95% CI; 0.13-0.81; P = 0.02). On average, following a diagnosis of
breast cancer, the annual risk of ipsilateral
breast cancer risk in BRCA mutation carriers is 1.2% per year. For women treated with
chemotherapy,
radiation therapy or
oophorectomy the risk is low, compared to women who did not receive any of these treatments.