Purpose: Colorectal cancer is the second leading cause of cancer deaths in the United States, with poor survival predicted by regional lymph node (LN) metastasis. The impact of LN ratio (LNR) on survival is unknown in this disease.
Patients and methods: We analyzed data from Intergroup trial 0089 of adjuvant chemotherapy for stage II and III patients with colon cancer, in which all patients received fluorouracil-based therapy. Survival was similar for all arms of the study, allowing us to evaluate all patients together. End points included overall survival (OS), cancer-specific survival (CSS), and disease-free survival (DFS). Multivariate analyses were performed on all patients and on groups according to LNR quartiles (LNR: < 0.05, 0.05 to 0.19, 0.2 to 0.39, and 0.4 to 1.0). Covariates included in the models were age, sex, tumor stage, grade, histology, number of positive LNs, number of LNs removed, and LNR.
Results: The median age was 63.7 years, and the median number of LNs removed was 11. In the multivariate analysis, LNR was a significant factor for OS, DFS, and CSS in patients with 10 to 15 LN and more than 15 LN removed but not for patients with less than 10 LN removed. Using quartiles, LNR maintained its significance for all three end points when patients were grouped by node status.
Conclusion: After curative resection for colorectal cancer, the LNR is an important prognostic factor and should be used in stratification schemes for future clinical trials investigating adjuvant treatments.