Patterns of completion axillary dissection for patients with cT1-2N0 breast cancer undergoing total mastectomy with positive sentinel lymph nodes

Background and Objectives: The ACOSOGZ0011 trial found that overall survival (OS) for patients with 1-2 positive nodes undergoing sentinel lymph node biopsy-alone (SLNB) was noninferior to completion axillary lymph node dissection (ALND), but excluded patients undergoing mastectomy. Our study examined patterns of ALND and its relationship with OS for SLNB-positive patients undergoing mastectomy.Methods: The National Cancer Database was queried (2010-2017) for patients with cT1-2N0 breast cancer undergoing mastectomy with positive sentinel lymph nodes. Clinical data were compared.Results: Of 20 001 patients, 11 574 (57.9%) underwent SLNB + ALND, and 8427 (42.1%) had SLNB-alone. The SLNB + ALND group had more positive nodes (mean 2.6 vs. 1.3, p < 0.001) and more frequently received nodal radiation (33.4% vs. 28.9%, p < 0.001). Patients diagnosed in later years were less likely to undergo ALND (2010: reference; 2017: odds ratio: 0.29, 95% confidence interval [CI]: 0.25-0.33, p < 0.001). ALND (hazard ratio [HR]: 0.97, 95% CI: 0.89-1.06, p = 0.49) and nodal radiation (HR: 0.92, 95% CI: 0.83-1.02, p = 1.06) were not independently associated with OS. Propensity-score matched 5-year OS was similar (SLNB + ALND: 90.9% vs. SLNB-alone: 90.3%, p = 0.65).Conclusion: For patients undergoing mastectomy for cT1-2N0 breast cancer with positive SLNB, SLNB-alone was common and increased over time. Axillary radiation was not routinely delivered in the SLNB-alone group. Completion ALND and nodal radiation were not associated with improved survival.