The prognostic superiority of log odds of positive lymph nodes in stage III colon cancer

Background: Literature showed that lymph node ratio (LNR) and total number of lymph nodes (TNODS) are independent prognostic factors in node-positive colon cancer. Our study assesses the prognostic superiority of the log odds of positive lymph nodes (LODDS) in the same patient population. Material and Methods: A total of 24,477 stage III colon cancer cases from the SEER registry were reviewed. Patients were categorized based on LNR into LNR1 to LNR4, according to cutoff points 0.07, 0.25, and 0.50, and based on LODDS into LODDS1 to LODDS5, according to cutoff points -2.2, -1.1, 0, and 1.1. The relative risk (RR), and 95% confidence interval (CI) were evaluated using the method of Kaplan-Meier and Cox model. Results: Patients with LNR4 could be classified into LODDS4 (61.4%) and LODDS5 (38.4%). The survival in these two groups was significantly different (5-year survival, 33.5% vs. 23.3%, p<0.0001). Univariate analysis showed that the higher LNR (RR=3.45, 95% CI=3.26-3.66) or low TNODS (RR=0.99, 95% CI=0.986-0.99) was significantly associated with poor survival. However, after adjusting for LODDS status, the association did not appear to be significant (LNR, RR=0.90, 95% CI=0.65-1.24, p=0.52; TNODS, RR=1.001, 95% CI=0.997-1.005, p=0.54). Conclusion: Colon cancer patients with LNR4 disease represent a heterogeneous group. The previously reported prognostic association of TNODS and LNR and outcome of stage III disease were confounded by LODDS.