The Number of Lymph Nodes Dissected in Breast Cancer Patients Influences the Accuracy of Prognosis

Abstract

Recent trials have suggested that axillary node dissection may not be warranted in some breast cancer patients with one to two positive nodes. Given that lymph node ratio (LNR; number of positive lymph nodes divided by the total examined) has been shown to be a significant prognostic factor, we sought to determine whether the number of nodes removed in this low risk population predicted survival. The National Cancer Database is a comprehensive clinical surveillance resource capturing 70% of newly diagnosed malignancies in the United States; 309,216 breast cancer patients diagnosed between 1998 and 2005, with tumors ≤5 cm and one to two positive nodes, formed the cohort of interest. Median age at diagnosis was 57 (range 18-90) years. Median tumor size was 2 (range 0.1-5) cm; 215,382 patients (69.7%) had one positive node, and 93,834 (30.3%) had two. The median number of lymph nodes examined was 11 (range 1-84). Patients were categorized into low (≤0.2), medium (0.21-0.65), or high (>0.65) LNR groups, with 228,822 (74%), 55,797 (18%), and 24,597 (8%) patients in each of these categories, respectively. Median follow-up was 54.1 months. Median overall survival (OS) for low, intermediate, and high LNR was 66.1, 61.1, and 56.5 months, respectively (p < 0.001). In a Cox model controlling for clinicopathologic and therapy covariates, LNR category remained a significant predictor of OS (p < 0.001). LNR is an independent predictor of OS in a low-risk population with one to two positive nodes and tumors ≤5 cm. Therefore, the number of lymph nodes excised may influence prognostic stratification.