Abstract PS2-01-15: Long-term outcomes of sentinel lymph node biopsy alone for breast cancer with residual axillary nodal disease (ypN+) following neoadjuvant chemotherapy: a systematic review and meta-analysis

Abstract Background: The optimal management of the axilla following neoadjuvant chemotherapy (NAC) for initially node-positive breast cancer (cN+) remains contentious, although there has been a trend towards de-escalating morbid axillary surgery under certain conditions. Clinically node-positive breast cancer that converts to node-negative (ypN0) following NAC is increasingly being managed by sentinel lymph node biopsy (SLNB) alone rather than by axillary lymph node dissection (ALND). Recent consensus by experts in St. Galen Ditsch et al, 2025 suggest SLNB alone may also be acceptable for low volume residual axillary nodal disease (ypN1) following NAC, although data to support the oncologic safety of this approach are limited. The aim of this meta-analysis was to evaluate the long-term oncologic outcomes of SLNB alone for residual axillary nodal disease following NAC. Methods: A systematic review and meta-analysis was conducted according to PRISMA guidelines. Medline (Ovid), Embase, and Cochrane Central Registry were systematically searched for studies comparing women undergoing SLNB or ALND following NAC for initially clinically node-positive breast cancer (cN+). Included studies reported one of the following outcomes: axillary recurrence (AR), locoregional recurrence (LRR), distant recurrence (DR), disease-free survival (DFS) or overall survival (OS). A random effects meta-analysis was used to calculate weighted pooled effect estimates (risk ratios, RR) for all outcomes, comparing SLNB alone with ALND for patients with residual nodal disease (cN+/ypN+). Variability across studies due to heterogeneity was estimated using I 2 statistics. Results: Fourteen observational studies were eligible for meta-analysis, providing data for 9,518 patients. The median age of the women included in the studies ranged from 47 to 53 years. Seven studies included only cN1 cases (pre-NAC), with 8 studies reporting outcomes for only ypN1 cases. The median number of sentinel lymph nodes retrieved in each study ranged from 2 to 6. The median follow-up time ranged from 28 to 108 months. The rates of axillary recurrence ranged from 0.2% to 7.8% across all included studies. Distant recurrence rates ranged from 15.7% to 38.6%. No significant differences were observed in AR between patients undergoing SLNB alone versus ALND following NAC: pooled RR 1.12 (95% CI: 0.72-1.74, I 2 =0.0%). Similarly, no significant differences were observed in LRR (RR 0.97, 95% CI: 0.68-1.37, I 2 =0.0%) nor overall mortality (RR 0.96, 95% CI: 0.65-1.42, I 2 =58.3%) between the two groups. However, the pooled risk of distant recurrence was lower for SLNB alone compared to the ALND group (RR 0.75, 95% CI: 0.60-0.95, I 2 =0.0%). Conclusions: This meta-analysis suggests that long-term outcomes of SLNB alone for breast cancer with residual axillary nodal disease following NAC are not inferior to those of ALND. AR rates were low across all included studies; the majority of recurrences were distant, questioning the need for aggressive axillary surgery for patients with low volume residual nodal disease. We await prospective data from several randomized clinical trials, including Alliance A011202 and MAC 19, to further guide axillary management in this group of patients. References: Ditsch et al (2025) St. Gallen/Vienna 2025 Summary of Key Messages on Therapy in Early Breast Cancer from the 2025 St. Gallen International Breast Cancer Conference. https://doi.org/10.1159/000546080 Citation Format: M. Rana, A. C. Weiss, A. D. Laws, C. Mita, T. King. Long-term outcomes of sentinel lymph node biopsy alone for breast cancer with residual axillary nodal disease (ypN+) following neoadjuvant chemotherapy: a systematic review and meta-analysis abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-01-15.