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Women who are newly diagnosed with breast cancer may consider contralateral prophylactic mastectomy (CPM) to reduce their future risk of cancer in their unaffected breast. Pre-surgical BRCA1/2 genetic testing can provide valuable risk information to guide this choice. However, little is understood about why BRCA1/2 mutation noncarriers, who are generally not at substantially elevated risk of contralateral disease, select CPM. We examined the uptake of CPM among breast cancer patients identified as BRCA1/2 mutation noncarriers (n = 92) as part of a larger prospective study of the impact of pre-surgical BRCA1/2 testing. Data obtained from self-report questionnaires and patient medical records were used to examine associations between theoretically relevant background and psychosocial factors and BRCA1/2 mutation noncarriers’ decisions to undergo CPM. Among BRCA1/2 mutation noncarriers, 25% (n = 23) elected to undergo CPM. Psychosocial factors including a self-reported physician recommendation for CPM, greater perceived contralateral breast cancer risk, and greater perceived benefits of CPM were all significantly associated with the uptake of CPM. A sizeable minority of BRCA1/2 mutation noncarriers choose to undergo CPM after learning their mutation status through pre-surgical genetic testing. BRCA1/2 mutation noncarriers’ cognitive perceptions and social influences appear to be important in shaping their decisions regarding CPM. This work highlights the importance of several psychosocial factors in influencing patients’ surgical decisions. Future research is needed that examines the formation of BRCA1/2 mutation noncarriers’ beliefs regarding their disease and available treatment options, and that characterizes the physician-patient communication that occurs in this complex decision-making context.

BRCA1/2 large rearrangement (LR) testing has been available to patients since 2006. Three existing models commonly used in cancer genetics clinical and research settings (BRCAPRO, Penn II and Myriad II) have not been assessed for their performance in predicting the presence of BRCA1/2 large genomic rearrangements in patients who do not have mutations detectable by the traditional Sanger sequencing approach. This study sought to determine if there is an optimal pre-test probability "cut off" value, calculated using these models, to optimize detection of large rearrangements (LRs). Our cohort consisted of 3,301 probands seen for genetic counseling and BRCA1/2 clinical testing from September 2006 to September 2011. A detailed personal and three-generation family history, including self-reported ethnicity, was taken as part of our standard clinical practice. We applied the BRCAPRO, Penn II, and Myriad II models to the probands with LRs. In our cohort of 3,301 probands, 150 carried a non-Ashkenazi mutation in BRCA1 or BRCA2. Seventeen unrelated probands carried a private BRCA1/2 LR (17/150, 11.3 % of all detectable non-AJ mutations). At a pre-test probability cutoff of 10 %, all three empiric risk models would have failed to identify almost 30 % of probands with LRs. Our study shows that BRCA1/2 LR testing should be offered to all women who meet criteria for BRCA1/2 sequence analysis.