Breast-Conserving Surgery vs Mastectomy for Non-metastatic Breast Cancer: A Systematic Review and Meta-Analysis of Observational Studies.

Breast cancer is a leading cause of cancer-related deaths among women worldwide, accounting for 15% of all cancer deaths. The decision between breast-conserving surgery (BCS) and mastectomy (MX) plays a fundamental role in the management of early-stage breast cancer. Improved survival rates are an essential outcome influencing these decisions. This systematic review and meta-analysis aim to compare the effectiveness of BCS versus MX in terms of survival and recurrence outcomes. We conducted a comprehensive search of PubMed MEDLINE, Web of Science, Cochrane, and EMBASE databases on 03/19/2024, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. Studies published from 1994 to 2024 comparing BCS with MX in breast cancer patients were included. The meta-analysis included 22 studies with a total sample size of 389,465 participants. For local recurrence, the random-effects model indicated an odds ratio (OR) of 1.65 (95% CI: 0.79-3.47, p = 0.19, I² = 70.6%). Regional recurrence showed an OR of 1.13 (95% CI: 0.26-5.03, p = 0.87, I² = 83.8%). For disease-free survival at five years, the hazard ratio (HR) was 0.78 (95% CI: 0.57-1.09, p = 0.14, I² = 98.2%), and at 10 years, the HR was 1.12 (95% CI: 0.79-1.58, p = 0.53, I² = 96.4%). Overall survival (OS) at five years showed a significant benefit for BCS (HR = 0.49, 95% CI: 0.34-0.71, p = 0.0001, I² = 98.8%), as did OS at 10 years (HR = 0.62, 95% CI: 0.42-0.91, p = 0.0149, I² = 98.8%). High heterogeneity was present in the survival outcomes (I² > 90%), limiting the robustness of the findings and suggesting variability across studies. BCS may offer comparable or superior survival outcomes compared to MX, but further research is needed to address the substantial heterogeneity and to develop personalized treatment guidelines. Notably, all 22 cohort studies were rated "good quality" on the Newcastle-Ottawa scale (NOS), supporting the overall reliability of the evidence.