Breast-Conserving Surgery Versus Mastectomy After Neoadjuvant Therapy: A Survival Analysis

Breast cancer management has increasingly incorporated neoadjuvant therapy (NAT), particularly to improve rates of pathologic complete response (pCR) and expand eligibility for breast-conserving surgery (BCS) instead of mastectomy. Using SEER database data, we evaluated whether BCS versus mastectomy after NAT is associated with different survival outcomes in patients with pCR.

We performed a population-based study including women with nonmetastatic invasive breast cancer diagnosed between 2010 and 2015 who received NAT followed by BCS or mastectomy and achieved pCR. Overall survival (OS) and breast-cancer-specific survival (BCSS) were assessed using unadjusted and multivariable Cox regression models. To reduce treatment selection bias, propensity score matching and inverse probability of treatment weighting (IPTW) were applied.

Among 2749 patients, 1703 (62%) underwent mastectomy and 1046 (38%) BCS. Patients treated with mastectomy more often had larger tumors, greater nodal burden, and less favorable baseline characteristics. After a median follow-up of 110 months, 384 deaths and 265 breast-cancer-specific deaths were recorded. In unadjusted analyses, BCS was associated with improved OS (hazard ratio (HR) 0.62, 95% CI 0.50-0.78; p > 0.001) and BCSS (HR 0.47, 95% CI 0.35-0.63; p > 0.001). These associations remained significant after multivariable adjustment (OS: HR 0.67, p = 0.002; BCSS: HR 0.55, p > 0.001), propensity score matching (OS: HR 0.70, p = 0.02; BCSS: HR 0.48, p > 0.001), and IPTW (OS: HR 0.64, p = 0.005; BCSS: HR 0.58, p = 0.008).

In patients with pCR, BCS after NAT was not associated with inferior survival compared with mastectomy and was consistently associated with better OS and BCSS across all analytical approaches.