Better contralateral breast cancer risk estimation and alternative options to contralateral prophylactic mastectomy

The incidence of contralateral prophylactic mastectomy (CPM) has increased among women with breast cancer, despite uncertain survival benefit and a declining incidence of contralateral breast cancer (CBC). Patient-related reasons for undergoing CPM include an overestimation of the risk of CBC, increased cancer worry, and a desire to improve survival. We summarize the existing literature on CBC risk and outcomes and the clinical benefit of CPM among women with unilateral breast cancer who have a low-to-moderate risk of developing a secondary cancer in the contralateral breast. Published studies were retrieved from the MEDLINE database with the keywords "contralateral breast cancer" and "contralateral prophylactic mastectomy". These include observational studies, clinical trials, survival analyses, and decision models examining the risk of CBC, the clinical and psychosocial effects of CPM, and other treatment strategies to reduce CBC risk. Studies that have evaluated CBC risk estimate it to be approximately 0.5% annually on average. Patient-related factors associated with an increased risk of CBC include carriers of BRCA1/2 mutations, young age at breast cancer, and strong family history of breast cancer in the absence of a BRCA1/2 mutation. Although CPM reduces the risk of CBC by approximately 94%, it may not provide a significant gain in overall survival and there is conflicting evidence that it improves disease-free survival among women with breast cancer regardless of estrogen receptor (ER) status. Therefore, alternative strategies such as the use of tamoxifen or aromatase inhibitors, which reduce the risk of CBC by approximately 50%, should be encouraged for eligible women with ER-positive breast cancers. Future research is needed to evaluate the impact of decision and educational tools that can be used for personalized counseling of patients regarding their CBC risk, the uncertain role of CPM, and alternative CBC risk reduction strategies.