Comparable Survival between Additional Radiotherapy and Local Surgery in Occult Breast Cancer after Axillary Lymph Node Dissection: A Population-based Analysis.

To investigate the clinical value of additional local treatment strategies in occult breast cancer (OBC) after axillary lymph node dissection (ALND). Patients diagnosed with OBC between 1990 and 2013 were included from the Surveillance, Epidemiology, and End Results registry database. The significant risk factors of cause-specific survival (CSS) and overall survival (OS) were identified using univariate and multivariate Cox regression analyses. We identified 980 patients, including 219 (22.3%), 252 (25.7%), 263 (26.8%), and 246 (25.1%) of patients underwent ALND, ALND + radiotherapy (RT), ALND + surgery (S) (mastectomy or breast-conserving surgery), and ALND + S + RT, respectively. Patients with younger age, diagnosed before 2000, advanced nodal stage, ER-negative disease, and PR-negative disease were more likely to undergo additional local treatment compared with ALND only. The 10-year rate CSS of the ALND only group was 57.2%, while that of the ALND + RT, ALND + S, and ALND + S + RT groups was 78.0%, 81.0%, and 71.5%, respectively ( < 0.001). The 10-year OS rate in the ALND only, ALND + RT, ALND + S, and ALND + S + RT groups was 46.0%, 69.5%, 66.1%, and 67.0%, respectively ( < 0.001). Multivariate analysis indicated that older age, advanced nodal stage, and ALND only were independent risk factors for decreased CSS and OS. CSS and OS among the groups including ALND + RT, ALND + S, and ALND + S + RT were not significantly different. Additional local treatment (local surgery or RT) improves survival outcomes compared with ALND only in OBC after ALND. ALND + RT may be the optimal local treatment for OBC due to no different in survival outcomes and cosmesis is better.