Lymph-node ratio is an independent prognostic factor in patients with stage III colorectal cancer: a retrospective study from the Middle East

Background: In this retrospective study, we evaluated the prognostic effect of positive lymph-node ratio (pLNR) on patients with stage III colorectal cancer (CRC). Our paper is the first analysis, to our knowledge, to deal with such data from the Middle East. Methods: We analyzed the clinicopathological data of 535 patients diagnosed with colorectal cancer at our institution between 1983 and 2003. The 164 patients diagnosed with stage III disease were divided into two categories based on lymph-node ratio (LNR) being the ratio of positive lymph nodes over total lymph nodes dissected: LNR <= 0.4 and LNR >0.4. We used Kaplan-Meier and Cox proportional hazard models to evaluate the prognostic effect of pLNR. Results: The 10-year survival rate for the patients with stage IIIA, IIIB and IIIC cancers were 76%, 56% and 0% respectively (P = 0.014). Using pLNR of 0.4 as the cutoff point was found to yield clinically and significant results, with a significant difference in the outcomes of patients with pLNR <= 0.4 compared to those with pLNR >0.4 (hazard ratio = 5.25, 95% confidence interval = 1.2 to 22.1, P = 0.02). Conclusion: The ratio-based staging (pLNR) of CRC is a more accurate and clinically useful prognostic method than the number of positive LNs resected or the total number of LNs retrieved for predicting the course of patients with stage III CRC.