Lymph Node Ratio: A Proposed Refinement of Current Axillary Staging in Breast Cancer Patients

Abstract

The optimal method for classifying lymph node (LN) status in breast cancer patients is unknown. We sought to determine if LN ratio (LNR) improves axillary staging. Kentucky Cancer Registry data (1996 to 2007) were used to compare LN categorization schemas. Overall survival (OS) was evaluated using the Kaplan-Meier method and log rank tests. Schemas included: LN positive (+) vs negative (-) disease, current American Joint Committee on Cancer (AJCC) staging (0 vs 1 to 3 vs 4 to 9 vs ≥10 LN+), and LNR 0 vs 0.01 to 0.20 vs 0.21 to 0.65 vs >0.65 (LN- vs low, intermediate, and high risk LN+ groups). There were 1,436 patients who had complete LN evaluation data: 880 (61.3%) were LN- and 556 (39.6%) were LN+; 309 (21.5%) had 1 to 3 positive LNs, 138 (9.6%) had 4 to 9 positive LNs, and 109 (7.6%) had 10 or more positive LNs. For LN+ patients, the median number of positive LNs was 3; median LNR was 0.23. The median follow-up was 65 months. LN status was associated with 5-year OS (91.3% and 73.3% for LN- and LN+ groups, respectively, p < 0.001). Increasing AJCC pN stage was associated with worse OS (5-year OS 80.5%, 75.3%, and 49.8% for pN1 to N3, respectively, p < 0.001). LNR was also associated with OS (5-year OS of 83.1%, 72.7%, and 52.7% for the low, intermediate, and high risk LN+ groups, respectively, p < 0.001). In subgroup analyses of patients in the 1 to 3 and 4 to 9 LN+ groups, OS was statistically associated with LNR (p = 0.021 and p = 0.016, respectively). On multivariable survival analysis, LNR was associated with OS, independent of AJCC categorization, p = 0.003. LNR was associated with OS, regardless of AJCC LN categories.