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.