Selecting Node-Positive Patients for Axillary Downstaging with Neoadjuvant Chemotherapy

Background Axillary lymph node dissection (ALND) can be avoided in node-positive patients who receive neoadjuvant chemotherapy (NAC) if three or more negative sentinel lymph nodes (SLNs) are retrieved. We evaluate how often node-positive patients avoid ALND with NAC, and identify predictors of identification of three or more SLNs and of nodal pathological complete response (pCR). Methods From November 2013 to July 2019, all patients with cT1-3, biopsy-proven N1 tumors who converted to cN0 after NAC received SLN biopsy (SLNB) with dual mapping and were identified from a prospectively maintained database. Results 630 consecutive N1 patients were eligible for axillary downstaging with NAC; 573 (91%) converted to cN0 and had SLNB, and 531 patients (93%) had three or more SLNs identified. Lymphovascular invasion (LVI; odds ratio [OR] 0.46, 95% confidence interval [CI] 0.24-0.87; p = 0.02) and increasing body mass index (BMI; OR 0.77, 95% CI 0.62-0.96 per 5-unit increase; p = 0.02) were significantly associated with failure to identify three or more SLNs. 255/573 (46%) patients achieved nodal pCR; 237 (41%) had adequate mapping. Factors associated with ALND avoidance included high grade (OR 2.51, 95% CI 1.6-3.94, p = 0.001) and receptor status (HR+/HER2- [referent]: OR 1.99, 95% CI 1.15-3.46 [p = 0.01] for HR-/HER2-, OR 3.93, 95% CI 2.40-6.44 [p < 0.001] for HR+/HER2+, and OR 8.24, 95% CI 4.16-16.3 [p < 0.001] for HR-/HER2+). LVI was associated with a lower likelihood of avoiding ALND (OR 0.28, 95% CI 0.18-0.43; p < 0.001). Conclusions ALND was avoided in 41% of cN1 patients after NAC. Increased BMI and LVI were associated with lower retrieval rates of three or more SLNs. ALND avoidance rates varied with receptor status, grade, and LVI. These factors help select patients most likely to avoid ALND.