Oncologic safety of sentinel lymph node biopsy using blue dye after neoadjuvant chemotherapy for breast cancer

Abstract Background Neoadjuvant chemotherapy in breast cancer is being increasingly employed. Sentinel lymph node biopsy is the current standard of care for axilla‐negative patients. However, evidence on extending application to post‐neoadjuvant setting and to converted node‐positive axilla is evolving. Methods This is a retrospective study, where we identify and compare patients who underwent sentinel node (SLN) biopsy mainly blue dye based before chemotherapy to those after neoadjuvant therapy (NAT). Results We find comparable SLN detection rate (96% vs. 91.5% in upfront vs. NAT) and comparable locoregional recurrence (4% vs. 6.7% in upfront vs. NAT). However, we detected a higher rate of positive non‐SLN after NAT in those who completed axillary clearance (50% vs. 72.5% in upfront vs. NAT). Also, there was a higher frequency of node positive disease in patients who failed SLN identification after NAT (78.5% of failed SLNB patients were node positive in clearance). On the other hand, neither detection rate (91.8% vs. 91.1% in pretherapy negative vs. converted) nor locoregional recurrence (9.7% vs. 3.5% in pretherapy negative vs. converted) were significantly higher in converted nodes (posttherapy cN0 after initial cN+ve). Conclusion SLNB in neoadjuvant setting has a similar detection rate and locoregional failure rate. Axillary clearance should be strongly considered if SLNB is positive or detection fails after neoadjuvant therapy. It is safe to apply SLNB in axilla converted patients even without pretherapy clipping.