Population-Based Analysis of Occult Primary Breast Cancer With Axillary Lymph Node Metastasis

BACKGROUND: Single-institution data suggest that treatment with radiation and axillary lymph node dissection (ALND) may be an appropriate alternative to mastectomy for TON+ breast cancer. Population-based multi-institutional data supporting this approach are lacking. METHODS: The cause-specific survival (CSS) and overall survival (OS) of women with TON+MO ductal, lobular, or mixed breast cancer in the Surveillance, Epidemiology, and End Results database from 1983 to 2006 were analyzed. Groups were defined as: 1) no ALND, mastectomy, or RT (observation); 2) ALND only; 3) mastectomy plus ALND with or without postmastectomy radiation (Mast); and 4) breast-conserving therapy (BCT) with ALND and radiation (BCT). RESULTS: In total, 750 of 770,030 patients with breast cancer had TON+MO disease (incidence, 0.10%), and 596 of those patients underwent ALND (79.5%), Patients who underwent Mast or BCT (n = 470) had a 10-year OS rate of 64.9% compared with 58.5% for patients who underwent ALND only (n = 126; P = .02) and 47.5% for patients who underwent observation only (n = 94; P = .04). The 10-year CSS rate was 75.7% for patients who underwent BCT versus 73.9% for patients who underwent Mast (P = .55). In multivariate analysis of CSS for patients who underwent Mast or BCT, the following factors were correlated with an unfavorable outcome: positive estrogen receptor status (hazard ratio [HR], 0.48; 95% confidence interval [Cl], 0.24-0.96; P = .04), >= 10 positive lymph nodes (HR, 5.7; 95%CI, 2.4-13.4; P <= .01), and <10 resected lymph nodes (HR, 42.9; 95%Cl, 1.2-7.1; P = .02). Mast did not improve CSS compared with BCT (HR, 1.09; 95%CI, 0.57-2.1; P = .79). CONCLUSIONS: Definitive locoregional treatment with either Mast or BCT improved the outcome of patients with TON+breast cancer, and no difference in survival was observed between the treatments. Cancer 2010;116:4000-6. (C) 2010 American Cancer Society.