Oncologic outcomes for different axillary staging techniques in nodal positive breast cancer undergoing neoadjuvant systematic treatment: A cancer registry study.

e12571 Background: The optimal axillary staging technique for patients with nodal positive breast cancer undergoing neoadjuvant systemic treatment (NAST) is unclear. Less invasive, targeted approaches like targeted axillary dissection (TAD) or sentinel-lymph node biopsy (SLNB) recently showed false-negative rates < 10% compared to axillary lymph node dissection (ALND). Oncologic outcomes, however, are unknown. Methods: We identified nodal positive breast cancer patients undergoing NAST from 2016 to 2021 with at least 1-year follow-up and available information regarding axillary staging from the state cancer registry of Baden-Wuerttemberg, Germany. Invasive disease-free survival (iDFS) was assessed using Kaplan-Meier statistics and multivariate cox regression models (adjusted for age, pN stage, pT stage, and tumor biologic subtype). Results: A total of 2403 patients with a median follow-up of 23.2-months after surgery were identified: 1963 underwent ALND, 407 underwent SLNB (in 230 cases, three or more sentinel nodes (SLNs) were removed and in 177 cases, 1-2 SLNs were removed), and 33 underwent TAD. The proportion of patients with pN+ stage within these four groups was 54%, 31%, 26%, and 35%, respectively ( P < 0.001). Significant differences in iDFS between the ALND, SLNB, and TAD groups were observed (log rank P = 0.046): iDFS 2 years after surgery was 74.5% (ALND), 80.2% (SLNB ≥3 removed SLNs), 85.6% (SLNB < 3 removed SLNs), and 88.4% (TAD), respectively. iDFS after 4 years was 61.5% (ALND), 69.1% (SLNB ≥3 removed SLNs), and 74.6% (SLNB < 3 removed SLNs), respectively. Multivariate cox regression analysis showed no significant influence of different axillary staging techniques on iDFS: HR 0.91 (95% CI 0.55 to 1.52) for SLNB with ≥3 removed SLNs, HR 0.99 (95% CI 0.59 to 1.67) for SLNB with < 3 removed SLNs (reference = ALND). Conclusions: This data suggests that ALND provides no benefit in terms of iDFS compared to targeted approaches like TAD or SLNB for patients with nodal positive breast cancer undergoing NAST. Future studies with longer-term follow-up are welcomed to fully inform this discussion.