Margin status, re-excision, and completion mastectomy after oncoplastic versus conventional breast-conserving surgery for breast cancer: a systematic review and meta-analysis

Abstract

Background Oncoplastic breast-conserving surgery (OBCS) may permit wider excision within a breast-conserving approach, but its effects on margin control and subsequent surgery remain uncertain. Methods We searched PubMed/MEDLINE, Embase, Web of Science Core Collection, Scopus, and the Cochrane Library from inception through 25 June 2026 for comparative studies of OBCS versus conventional breast-conserving surgery (BCS). Primary outcomes were initial positive margin, re-excision, completion/conversion mastectomy, and any margin-related reoperation. Secondary outcomes were negative/clear margin, recurrence, and complications. Risk ratios (RRs) with 95% confidence intervals (CIs) were pooled using random-effects Mantel–Haenszel models. Methodological quality was assessed using the Newcastle–Ottawa Scale. The protocol was registered in PROSPERO (CRD420261439265). Results Forty-eight comparative studies comprising 124,903 BCS observations were included (28,085 OBCS; 96,818 conventional BCS). Compared with conventional BCS, OBCS was associated with lower risks of initial positive margin (RR 0.57, 95% CI 0.40–0.80), re-excision (RR 0.59, 95% CI 0.46–0.77), completion/conversion mastectomy (RR 0.62, 95% CI 0.43–0.90), and any margin-related reoperation (RR 0.63, 95% CI 0.51–0.78). OBCS was also associated with a higher likelihood of achieving negative/clear margins (RR 1.07, 95% CI 1.04–1.11). No significant between-group differences were observed in local recurrence/ipsilateral breast tumor recurrence or locoregional recurrence. Overall complication risk was higher in the primary analysis, but the association was attenuated to borderline statistical significance after exclusion of registry or administrative-database cohorts. Conclusions OBCS was associated with more favorable margin-related outcomes and fewer margin-driven reoperations, without a detectable increase in recurrence. These findings support selective use of OBCS as a margin-control and breast-preservation strategy in appropriately selected patients. However, complication estimates should be interpreted cautiously because reporting and ascertainment varied across study designs. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420261439265, identifier CRD420261439265.