Contralateral Axillary Nodal Metastases: Stage IV Disease or a Manifestation of Progressive Locally Advanced Breast Cancer?

BACKGROUND. Contralateral axillary nodal metastases (CAM) is classified as stage IV disease, although many centers treat CAM with curative intent. We hypothesized that patients with CAM, treated with multimodality therapy, would have improved overall survival (OS) versus patients with distant metastatic disease (M1) and similar OS to those with locally advanced breast cancer (LABC). METHODS. Using the NCDB (2004–2016), we categorized adult patients with node-positive breast cancer into three study groups: LABC, CAM, and M1. Kaplan-Meier curves were used to visualize the unadjusted OS. Cox proportional hazards models were used to estimate the association of study group with OS. RESULTS. A total of 94,487 patients were identified: 122 with CAM, 12,325 with LABC, and 82,040 with M1 (median follow-up 63.6 months). LABC and CAM patients had similar histology and rates of chemotherapy and endocrine therapy receipt. However, the CAM group had significantly larger tumors, more estrogen-receptor expression, higher T-stage, and more mastectomies than the LABC group. Compared with M1 patients, CAM patients were more likely to have grade 3 and cT4 tumors. Patients with CAM and LABC had similar 5-year unadjusted OS and significantly improved OS vs M1 patients. After adjustment, LABC and CAM patients continued to have similar OS and better OS vs M1 patients. CONCLUSIONS. CAM patients who receive multi-modal therapy with curative intent may have OS more comparable to LABC patients than M1 patients. Out data support a reevaluation of whether CAM should remain classified as M1, as N3 may better reflect disease prognosis and treatment goals.