Background: 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.
Methods: 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.
Results: 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).
Conclusions: 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.