LAUSR

Background Neoadjuvant chemotherapy (NAC) for breast cancer increases breast-conserving surgery (BCS) rates, but many women opt for mastectomy with contralateral prophylactic mastectomy (CPM). Here we evaluate factors associated with CPM use in women undergoing mastectomy post-NAC. Methods A retrospective institutional NAC database review identified women with clinical stage I-III, unilateral invasive breast cancer undergoing unilateral mastectomy (UM) or CPM mastectomy from 9/2013 to 12/2017. Clinical/pathologic characteristics, imaging, and presence of contraindications to BCS post-NAC were compared, with subset analysis of BCS candidates. The multivariable analysis was adjusted for potential confounders. Results Five hundred sixty-nine women underwent mastectomy after NAC, 297 (52%) UM and 272 (48%) CPM. On univariable analysis, younger age, BRCA +, lower pre-NAC clinical stage, pathologic complete response, and axillary surgery extent were associated with CPM (all p  < 0.01). Favorable post-NAC clinical factors of no residual palpable disease, clinically negative nodes, complete response on breast imaging, and no post-NAC contraindication to BCS were also associated with CPM (all p  < 0.01). On multivariable analysis, young age (odds ratio [OR] 0.93, 95% confidence interval [CI] 0.91–0.95), lower pre-NAC stage (OR 0.51, 95% CI 0.34–0.77), and no contraindication to BCS (OR 3.12, 95% CI 2.02–4.82) were significantly associated with CPM. Among the 203 (35%) women who had no contraindications to BCS post-NAC, 145 (71%) underwent CPM. BRCA + and family history were reasons more frequently cited for mastectomy among CPM than UM ( p  < 0.001). Conclusions CPM was performed in 48% of women undergoing mastectomy after NAC; younger women with earlier-stage cancers were more likely to undergo CPM. While increased use of CPM in women with more favorable disease is medically appropriate, our findings indicate a lost opportunity for use of BCS.