De-Escalation of Nodal Surgery in Clinically Node-Positive Breast Cancer.

Importance: Increasing evidence supports the oncologic safety of de-escalating axillary surgery for patients with breast cancer after neoadjuvant chemotherapy (NAC). Objective: To evaluate the oncologic outcomes of de-escalating axillary surgery among patients with clinically node (cN)-positive breast cancer and patients whose disease became cN negative after NAC (ycN negative). Design, Setting, and Participants: In the NEOSENTITURK MF-1803 prospective cohort registry trial, patients from 37 centers with cT1-4N1-3M0 disease treated with sentinel lymph node biopsy (SLNB) or targeted axillary dissection (TAD) alone or with ypN-negative or ypN-positive disease after NAC were recruited between February 15, 2019, and January 1, 2023, and evaluated. Exposure: Treatment with SLNB or TAD after NAC. Main Outcomes and Measures: The primary aim of the study was axillary, locoregional, or distant recurrence rates; disease-free survival; and disease-specific survival. Number of axillary lymph nodes removed was also evaluated. Results: A total of 976 patients (median age, 46 years [range, 21-80 years]) with cT1-4N1-3M0 disease underwent SLNB (n = 620) or TAD alone (n = 356). Most of the cohort had a mapping procedure with blue dye alone (645 [66.1%]) with (n = 177) or without (n = 468) TAD. Overall, no difference was found between patients treated with TAD and patients treated with SLNB in the median number of total lymph nodes removed (TAD, 4 [3-6] vs SLNB, 4 [3-6]; P = .09). Among patients with ypN-positive disease, those who underwent TAD were more likely to have a lower median lymph node ratio (TAD, 0.28 [IQR, 0.20-0.40] vs SLNB, 0.33 [IQR, 0.20-0.50]; P = .03). At a median follow-up of 39 months (IQR, 29-48 months), no significant difference was found in the rates of ipsilateral axillary recurrence (0.3% [1 of 356] vs 0.3% [2 of 620]; P ≥ .99) or locoregional recurrence (0.6% [2 of 356] vs 1.1% [7 of 620]; P = .50) between the TAD and SLNB groups, with an overall locoregional recurrence rate of 0.9% (9 of 976). The initial clinical tumor stage, pathologic complete response, and use of blue dye alone as a mapping procedure were not associated with the outcome. Even though patients with TAD demonstrated an increased disease-free survival rate compared with the SLNB group, this difference did not reach statistical significance (94.9% vs 92.6%; P = .07). Factors associated with decreased 5-year disease-specific survival were cN2-3 axillary stage (cN1, 98.7% vs cN2-3, 96.8%; P = .03) and nonluminal type tumor pathologic characteristics (luminal, 98.9% vs nonluminal, 96.9%; P = .007). Conclusions and Relevance: The short-term results suggest very low rates of axillary and locoregional recurrence in a select group of patients with cN-negative disease after NAC treated with TAD alone or SLNB alone followed by regional nodal irradiation regardless of the SLNB technique or nodal pathology. Whether TAD might provide a clear survival advantage compared with SLNB remains to be proven in studies with longer follow-up.