Long-term Results of the Expanded Application of the ACOSOG Z0011 Trial for Patients with Breast Cancer

Background: Axillary lymph node dissection (ALND), while historically pivotal in staging and prognosis for breast cancer, is associated with considerable morbidity. The American College of Surgeons Oncology Group (ACOSOG) Z0011 trial shifted surgical paradigms; however, its generalizability to Asian populations and extended clinical scenarios remains underexplored. This study aimed to evaluate the long-term oncologic safety of omitting ALND in the Korean cohort of patients with early-stage breast cancer, including populations not originally encompassed by the ACOSOG Z0011 trial, such as those undergoing mastectomy, harboring non-sentinel lymph node (non-SLN) metastases, or receiving neoadjuvant chemotherapy (NACT). Methods: This retrospective, single-center cohort study included 505 patients with T1-2 invasive breast cancer and ≤2 metastatic axillary lymph nodes (including SLN and non-SLN), selected from a total of 2,506 surgical cases performed between January 2006 and May 2018. For the NACT subgroup, the enrollment period extended through December 2022. Mean follow-up duration was 9.0±3.9 years. The exposures included a comparison between sentinel lymph node biopsy (SLNB) alone and ALND. The primary endpoints were 10-year relapse-free survival (RFS) and overall survival (OS), evaluated across the total cohort and within three predefined subgroups: SLN(-)/non-SLN(+), mastectomy, and NACT recipients. Results: Among 505 eligible patients, 102 and 403 underwent SLNB alone and ALND, respectively. No statistically significant differences were observed in 10-year RFS (83.7% vs. 79.9%, p = 0.23) or OS (94.6% vs. 93.3%, p = 0.52). Subgroup analyses similarly demonstrated noninferiority of SLNB alone, even in patients with non-SLN metastases, those undergoing mastectomy, or receiving NACT. Conclusions: This study supports the oncologic safety of extending SLNB-only management to select Korean patients with breast cancer beyond conventional Z0011 criteria. These findings reinforce the paradigm shift toward de-escalation of axillary surgery and underscore the necessity for prospective, multicenter validation. Trial registration: Not applicable – this study is a retrospective analysis.