Contralateral breast cancer risk in patients with familial breast cancer who tested negative for BRCA1 and BRCA2.

1013 Background: A high incidence of contralateral breast cancer has been reported in patients with BRCA1or BRCA2 mutations while the risk in patients with familial non-BRCA-associated breast cancer remains unclear. This study was undertaken to estimate the risk for contralateral breast cancer in patients of BRCA1- and BRCA2-negative high risk families and to determine predictive risk factors. Methods: A retrospective, multicenter, cohort study was performed from 1996 until 2010 and comprised 3,580 women with unilateral breast cancer from 2,793 high-risk families who were tested negative for BRCA1 or BRCA2 mutations. Kaplan-Meier analysis was used to estimate age-dependent contralateral breast cancer risks. Cox regression analysis was applied to assess the impact of age at first breast cancer on contralateral breast cancer risk. Results: The cumulative risk for contralateral breast cancer 25 years after first breast cancer was 19% (95%CI 16% to 22%) for patients from families with non-BRCA-associated breast cancer. This rate is significantly lower compared to BRCA1 and BRCA2 mutation carriers (46% and 36%, respectively). Younger age at first breast cancer was associated with a significantly higher risk of contralateral breast cancer. After 25 years, 29% (95%CI 20% to 37%) of non-carriers who were younger than 40 years of age at first breast cancer developed contralateral breast cancer, compared with only 15% (95%CI 10% to 20%) of those who were older than 50 years. These incidences are similar to patients with sporadic breast cancer. Conclusions: Contralateral breast cancer risk in patients with familial non-BRCA-associated breast cancer is similar to the risk in patients with sporadic breast cancer and depends on age at first breast cancer. Therefore, risk-reducing contralateral mastectomy does not seem to be adequate for non-BRCA1/2 breast cancer patients.