Survival and Extent of Breast Surgery in Patients with Complete Response After Neoadjuvant Therapy: A Retrospective Analysis from the EUSOMA Database

Background: Optimal management of breast cancer (BC) patients with pathological complete response (pCR) after neoadjuvant therapy (NAT) remains debated. We performed a retrospective analysis to evaluate whether the extent of surgery influences survival outcomes in this patient population. Methods: Using the EUSOMA database, we retrospectively collected data of women with pCR after NAT, excluding those with BRCA1/2 mutations. The cohort was stratified by surgery type, i.e., breast-conserving surgery (BCS) or mastectomy. Relapse-free survival (RFS) and overall survival (OS) were compared using Cox regression. Results: Of 467 patients, 327 (70.0%) underwent BCS and 140 (30.0%) underwent mastectomy. Women treated with mastectomy were more likely to have multifocal tumors and advanced disease. After a median follow-up of 5.6 years, 7.3% of patients experienced BC recurrence. Axillary nodal involvement (cN+) and mastectomy were independently associated with recurrence, occurring in 11.4% of cN+ compared to 3.7% of cN0 patients (HR 3.02; 95% CI: 1.40–6.51; p = 0.005) and in 12.5% of mastectomy vs. 5.2% of BCS patients (HR 2.08; 95% CI: 1.05–4.11; p 0.035). cN+ patients also showed significantly higher mortality rates (9.4% vs. 1.6% of cN0; HR 6.16; 95%CI: 2.09–18.17; p= 0.001). However, surgery type did not impact OS. Conclusion: In this cohort of BC patients with pCR after NAT, BCS was not associated with a higher risk of recurrence compared with mastectomy. Baseline nodal involvement independently predicted recurrence and mortality; however, the type of surgery did not impact OS. These findings support BCS as a safe treatment option for this patient population.