Breast tumor location in BRCA mutation carriers and implications for prevention.

Abstract

e13048 Background: Although pathogenic mutations in the BRCA gene are known to confer a high risk of breast cancer, close to 65% of mutation carriers do not opt for prophylactic mastectomy. These women are managed with intense screening, which does not aid in prevention. Breast reduction mammoplasty is a surgical technique shown to reduce breast cancer risk (0.39-0.61 relative risk reduction), and can be modified to target specific areas of the breast. Given that most sporadic breast cancers involve the upper outer quadrant, we wondered if a majority of tumors in BRCA mutation carriers would also be confined to one quadrant, or if they would be equally distributed throughout the breast given the high baseline risk present. Identifying a particularly high risk area of the breast could potentially allow for the use of targeted cosmetic mammoplasty as a novel method of risk reduction. Methods: We reviewed imaging reports on 103 consecutive patients with BRCA mutations and invasive breast cancer, and categorized tumor location by quadrant. Tumors spanning > 1 quadrant were classified as being in both. Bilateral cancers were counted separately. Categorical variables were compared with the chi-squared test. Results: Mean age at breast cancer diagnosis was 44 years. Mean tumor size was 2.2 cm (0.1-7cm) with mean distance from the nipple of 4.8 cm (1-12 cm). 92% of tumors were invasive ductal carcinoma, 46% were hormone receptor positive, 10% Her2 positive, and 44% triple negative. 70% of the tumors were unicentric. Tumors were significantly more likely to be in the upper outer quadrant (54%, with the other quadrants having 11-17% of tumors respectively) whether or not multicentric tumors were included in the analysis (p < 0.00001). Her2 positive tumors were more likely to be multicentric than other subtypes (p = 0.021). Conclusions: More than half of breast cancers in BRCA mutation carriers form in the upper outer quadrant, suggesting that breast reduction mammoplasty targeting removal of the upper outer quadrant could significantly reduce breast cancer risk. For those women who choose not to have prophylactic mastectomies or are not yet ready, these data support an intermediate step to help decrease breast cancer risk, which warrants further study.