Margin positivity and re-excision after breast-conserving surgery following neoadjuvant chemotherapy: A systematic review and meta-analysis.

Neoadjuvant chemotherapy (NACT) is increasingly used to facilitate breast-conserving surgery (BCS) in patients with early-stage and locally advanced breast cancer. However, tumour response to NACT is heterogeneous, and comparative studies have reported higher rates of margin involvement and re-excision compared with primary surgery. Despite its clinical significance, the incidence of positive margins and rates of re-excision remain incompletely defined. A systematic review and meta-analysis was conducted in accordance with PRISMA guidelines. PubMed, Embase, and Scopus were searched for studies reporting tumour-on-ink margin positivity following BCS after NACT. A random-effects meta-analysis was performed to estimate pooled rates of margin positivity and re-excision. Seven retrospective cohort studies comprising 3962 patients were included, with six studies (3855 patients) eligible for quantitative synthesis. The pooled tumour-on-ink margin positivity rate following index BCS after NACT was 9.7% (95% CI 5.8-13.6%). The pooled re-excision rate was 14.0% (95% CI 0.0-30.6%), with substantial between-study heterogeneity. Re-excision rates varied widely, likely reflecting differences in institutional practice and thresholds for reoperation. Residual DCIS and invasive lobular carcinoma were the clinicopathological features most consistently associated with higher rates of margin positivity and re-excision. Tumour-on-ink margin positivity following BCS after NACT is comparable to that reported following primary surgery, while re-excision rates are higher and more variable. Improved risk stratification may assist surgical planning and patient counselling following NACT.