Nodal Recurrence in Patients With Node-Positive Breast Cancer Treated With Sentinel Node Biopsy Alone After Neoadjuvant Chemotherapy-A Rare Event.

Importance: Prospective trials have demonstrated sentinel lymph node (SLN) false-negative rates of less than 10% when 3 or more SLNs are retrieved in patients with clinically node-positive breast cancer rendered clinically node-negative with neoadjuvant chemotherapy (NAC). However, rates of nodal recurrence in such patients treated with SLN biopsy (SLNB) alone are unknown because axillary lymph node dissection (ALND) was performed in all patients, limiting adoption of this approach.

Objective: To evaluate nodal recurrence rates in a consecutive cohort of patients with clinically node-positive (cN1) breast cancer receiving NAC, followed by a negative SLNB using a standardized technique, and no further axillary surgery.

Design, Setting, And Participants: From November 2013 to February 2019, a cohort of consecutively identified patients with cT1 to cT3 biopsy-proven N1 breast cancer rendered cN0 by NAC underwent SLNB with dual tracer mapping and omission of ALND if 3 or more SLNs were identified and all were pathologically negative. Metastatic nodes were not routinely clipped, and localization of clipped nodes was not performed. The study was performed in a single tertiary cancer center.

Intervention: Omission of ALND in patients with cN1 breast cancer after NAC if 3 or more SLNs were pathologically negative.

Main Outcome And Measures: The primary outcome was the rate of nodal recurrence among patients with cN1 breast cancer treated with SLNB alone after NAC.

Results: Of 610 patients with cN1 breast cancer treated with NAC, 555 (91%) converted to cN0 and underwent SLNB; 234 (42%) had 3 or more negative SLNs and had SLNB alone. The median (IQR) age of these 234 patients was 49 (40-58) years; median tumor size was 3 cm; 144 (62%) were ERBB2 (formerly HER2)-positive, and 43 (18%) were triple negative. Most (212 [91%]) received doxorubicin-based NAC; 205 (88%) received adjuvant radiotherapy (RT), and 164 (70%) also received nodal RT. At a median follow-up of 40 months, there was 1 axillary nodal recurrence synchronous with local recurrence in a patient who refused RT. Among patients who received RT (n = 205), there were no nodal recurrences.

Conclusions And Relevance: This cohort study found that in patients with cN1 disease rendered cN0 with NAC, with 3 or more negative SLNs with SLNB alone, nodal recurrence rates were low, without routine nodal clipping. These findings potentially support omitting ALND in such patients.