Metastatic lymph node ratio as a prognostic indicator in patients with stage IV colon cancer undergoing resection

Background: It has been shown that the metastatic lymph node ratio (LNR, metastatic LNs divided by the total number of retrieved LNs) significantly affects the prognosis of patients with non-stage IV and some curative stage IV colon cancer undergoing curative resection. In this study, we aimed to evaluate the role of the LNR as a predictor of prognosis in patients with stage IV colon cancer undergoing curative or palliative resection. Patients and Methods: We conducted a retrospective study of 424 patients who were initially diagnosed with stage IV colon cancer at the Sun Yat-Sen University Cancer Center from 2003 to 2014. The patients were divided into the curative and palliative primary tumor resection groups with regional lymph nodes harvest. The median value was used as the cutoff for the LNR. Overall survival (OS) was assessed with the Kaplan-Meier method and log-rank test. Multivariate analysis was performed to identify the prognostic factors for OS. Results: The cutoff value for the LNR was 0.2. A total of 71 and 353 patients were classified as being in the curative and palliative resection groups, respectively. Patients in the palliative resection group showed higher pretreatment levels of carbohydrate antigen 19-9 (CA199; P = 0.014), a deeper infiltration of the primary tumor (P = 0.049), a lower regional lymph node harvest (i.e., total lymph node yield [TLN] ≤ 11; P = 0.001), and more extensive metastasis (P = 0.006). Among all patients, initial elevated CA199 levels, a TLN≤11, a negative lymph nodes (NLN) ≤7, and a LNR ≤0.2 were significantly associated with an unfavorable prognosis. OS was significantly longer in patients with a low LNR in both groups (P = 0.008 and P = 0.001, respectively). The LNR was an independent prognostic indicator in patients with stage IV colon cancer, with a hazard ratio (HR) of 1.47 (95% confidence interval [CI] 1.14-1.91; P = 0.003) in total population, and an HR of 1.43 (95% CI 1.09-1.86; P = 0.009) in patients with palliative resection. Conclusion: The LNR can be used as an independent prognostic factor in patients with stage IV colon cancer patients undergoing resection.