Association of a high versus low number of negative lymph nodes removed with survival and recurrence-free survival after lymph node dissection in breast cancer: a systematic review and meta-analysis of observational studies.

Although most studies have reported that a high number of negative lymph nodes (NLNs) at surgery can be associated with improved overall survival (OS) in patients with breast cancer (BC), the effect size was reported differently in several studies, which may be due to the small sample size of the primary studies. This systematic review and meta-analysis aimed to investigate the association of a high number of NLNs removed during surgery with OS and recurrence-free survival (RFS) in BC patients who are candidates for axillary lymph node dissection. We searched the PubMed, Embase, Scopus, Google Scholar, and Web of Science databases, as well as study references, to identify related articles published from the beginning of 2000 to October 2024. Based on sensitivity analysis, the removal of ≥ 10 NLNs was defined as the high number of NLNs removed group, and the removal of < 10 NLNs was defined as the low number of NLNs removed group. The heterogeneity between studies was assessed using Cochran's Q and I2 tests. Publication bias was assessed using Egger's test. Ultimately, 14 studies encompassing 36,576 BC patients were included. A pooled estimate of 14 studies showed that a high number of NLN removed compared to a low number of NLN removed was significantly associated with improved 5-year OS (HR: 0.82, 95% CI: 0.74, 0.90), I2 = 93.8) and RFS rate (HR:0.76, CI: 0.765, 0.86), I2 = 86.3). A higher number of NLNs removed during surgery in BC patients who are candidates for axillary lymph node dissection appears to be associated with improved OS and RFS.