Sentinel lymph node biopsy versus axillary lymph node dissection after neoadjuvant chemotherapy in breast cancer: a systematic review and meta-analysis

The optimal axillary management after neoadjuvant chemotherapy (NACT) in breast cancer remains debated. When compared to axillary lymph node dissection (ALND), sentinel lymph node biopsy (SLNB) alone has been suggested to lower morbidity. We performed a systematic review and meta-analysis to compare the oncologic outcomes (survival and recurrence) of SLNB alone with those of ALND ± SLNB after NACT. PubMed/MEDLINE, Embase, Scopus, the Cochrane Library, ClinicalTrials.gov and WHO ICTRP were searched from inception to 30 March 2026 (PROSPERO registration CRD420261490493). Randomised and non-randomised comparative studies of SLNB alone versus ALND ± SLNB in patients with breast cancer receiving NACT were eligible. Outcomes were axillary recurrence (AR), disease-free survival (DFS), local and locoregional recurrence (LRR), distant recurrence, breast cancer-specific mortality and overall survival (OS). Risk of bias was assessed with ROBINS-I and the certainty of evidence with GRADE. Mantel-Haenszel random-effects models were used to compute pooled risk ratios (RR) with 95% confidence intervals (CIs), results were stratified by baseline clinical nodal status, and heterogeneity was assessed with the I² statistic. Five non-randomised comparative studies (2,647 patients) were included; no randomised trial was identified among the 906 records retrieved by the searches. The pooled estimate for AR was higher with SLNB alone but imprecise (RR 1.45, 95% CI 0.75 to 2.79; I²=0%; five studies), and estimates for LRR (RR 0.86, 95% CI 0.60 to 1.22; I²=0%; five studies) and local recurrence (RR 0.73, 95% CI 0.38 to 1.40; I²=43%; four studies) were compatible with both fewer and more events. Crude estimates were lower with SLNB alone for OS (RR 0.48, 95% CI 0.32 to 0.72; I²=60%; five studies), DFS (RR 0.53, 95% CI 0.31 to 0.90; I²=78%; three studies), breast cancer-specific mortality (RR 0.39, 95% CI 0.25 to 0.59; I²=0%; two studies) and distant recurrence (RR 0.40, 95% CI 0.20 to 0.79; I²=85%; three studies), but the studies were at serious or critical risk of bias from confounding, and the groups differed in baseline prognostic factors. The certainty of evidence was very low for all outcomes, so the evidence is very uncertain about the effect of SLNB alone on each outcome. Results are presented separately for studies enrolling only cN+ patients and studies enrolling cN0 or mixed populations. Based on five non-randomised studies, the evidence is very uncertain about the effect of SLNB alone compared with ALND ± SLNB on survival and recurrence in breast cancer patients treated with NACT. The pooled estimates do not exclude a clinically important increase in axillary recurrence with SLNB alone, and the lower crude mortality and distant recurrence estimates most likely reflect patient selection. These results do not establish equivalence and highlight the need for randomised or well-adjusted prospective comparative studies, analysed by baseline nodal status, before axillary de-escalation is supported in the neoadjuvant setting.