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 T0N+ 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 T0N+M0 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 T0N+M0 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 [CI], 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%CI, 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 T0N+breast cancer, and no difference in survival was observed between the treatments. Cancer 2010. © 2010 American Cancer Society.