A Multi-Institutional Analysis of Contralateral Axillary Metastases: Advanced Local-Regional Disease Divergent from Stage IV Breast Cancer.

Background: Contralateral axillary metastasis (CAM) is a rare event and is considered stage IV disease. We sought to evaluate outcomes in a CAM cohort treated with curative intent and contemporary systemic and locoregional therapy.

Patients and methods: A retrospective multi-institutional review was conducted from 2016 to 2022 of patients with CAM who underwent axillary surgery. Survival outcomes were compared with those with locally advanced breast cancer (LABC) and metastatic breast cancer (MBC).

Results: In total, 754 patients were included in the study (63 CAM, 188 LABC, and 503 MBC). The median age at CAM diagnosis was 62 years [(interquartile range (IQR) 49.2-69.3)], and the majority demonstrated invasive ductal histology (74.6%). Over half of the patients with CAM received neoadjuvant chemotherapy (55.6%) followed by axillary dissection (82.5%) and adjuvant radiation (74.6%) in most cases. On unadjusted analysis, the LABC cohort demonstrated the highest 3-year unadjusted overall survival (OS) (89.4%), followed by CAM (79.7%) and MBC (53%) (p < 0.001). On multivariable analysis adjusting for age, race/ethnicity, insurance, and hormone receptor status, patients with MBC had inferior survival compared with LABC [hazard ratio (HR) 6.59, 95% confidence interval (CI) 4.22-10.28, p < 0.001], while CAM had similar survival to that seen in LABC (HR 2.13, 95% CI 0.82-5.52, p = 0.12).

Conclusions: Survival was higher for patients with CAM compared with MBC and was similar to patients with LABC. Though the LABC group demonstrated better recurrence-free survival than the CAM group, these numbers were comparable within the first 2 years of follow-up. Our data provides additional support for the consideration of curative intent management for patients with CAM.