PURPOSE: This study was designed to assess the prognostic value of the lymph node ratio in patients with colon cancer treated by colorectal specialists.
METHODS: Three hundred and sixty-two Stage III consecutive cases were analyzed based on quartiles: lymph node ratio 1 (>0 and <0.06); lymph node ratio 2 (between 0.06 and 0.12); lymph node ratio 3 (>0.12 and <0.25); lymph node ratio 4 (≥0.25).
RESULTS: Disease-free survival rates were: lymph node ratio 1, 75.5%; lymph node ratio 2, 74.2%; lymph node ratio 3, 73.2%; and lymph node ratio 4, 40.1%. Similar differences were observed for cancer-specific and overall survival rates. Cases with lymph node ratio ≥0.25 had higher hazard ratios than cases with lymph node ratio <0.25 in terms of disease-free survival (2.8, P < 0.001), cancer-specific survival (3.1, P = 0.0001), and overall survival (2.2, P = 0.0001). The hazard ratio of cases with up to three positive nodes and lymph node ratios ≥0.25 was higher than that of cases with up to three positive nodes and lymph node ratios <0.25 in terms of disease-free survival (3.1, P = 0.003), cancer-specific survival (3.5, P = 0.002), and overall survival (2.4, P = 0.02). Similar differences were found for cases with more than three positive nodes. Lymph node ratio, but not number of positive nodes, had independent prognostic value in multivariate analysis. No interaction between these two variables was found.
CONCLUSION: A lymph node ratio ≥0.25 was an independent prognostic factor in Stage III colon adenocarcinoma regardless of the number positive nodes. It modified outcomes predicted by the current staging system.