Identifying subgroups of ypN1 breast cancer patients who may exempt from axillary lymph node dissection after neoadjuvant chemotherapy: insights from a large cohort study.

Background: In patients with breast cancer staged ypN1 after neoadjuvant chemotherapy (NAC), there is limited evidence-based guidance regarding exemption from axillary lymph node dissection (ALND).

Methods: This study analyzed ypN1 breast cancer patients post-NAC from the Surveillance, Epidemiology, and End Results databases. Patients were categorized into the breast-conserving surgery (BCS) group and the total mastectomy (TM) group, and further divided by the number of positive lymph nodes (LNs). The effects of three axillary management strategies, ALND, sentinel lymph node biopsy combined with radiotherapy (SLNB + RT), and ALND + RT were compared. The overall survival (OS) and breast cancer-specific survival (BCSS) of all subgroups and their independent risk factors were analyzed. Independent prognostic factors selected from multivariate Cox analysis were utilized to create nomograms for predicting OS and BCSS.

Results: A total of 3641 patients were involved, with 1331 in the BCS group and 2310 in the TM group. In the TM group, patients with 3 residual positive LNs exhibited significant improvements in OS and BCSS when treated with ALND + RT. For patients with 1 or 2 residual positive LNs in the TM group and all BCS patients, no significant survival differences in survival outcomes were observed among the three axillary management methods. The accuracy of the nomograms was validated via calibration curves, receiver operating characteristic curves, and decision curve analysis curves.

Conclusion: For TM group patients with 3 residual positive LNs after NAC, ALND + RT is recommended. For other subgroups of ypN1 patients, SLNB + RT can be considered an alternative to ALND. The nomogram developed to predict OS and BCSS in ypN1 breast cancer patients demonstrated excellent predictive ability.