Prognostic accuracy of different lymph node staging system in predicting overall survival in stage IV colon cancer

Purpose With emphasis of surgical management, the lymph node (LN) status has been advocated to predict prognosis in colon cancer with distant metastatic. Therefore, we tend to compare the prognostic performance of American Joint Committee on Cancer (AJCC) N-staging relative to lymph node ratio (LNR), log odds of metastatic lymph nodes (LODDS), and N-score in stage IV colon cancer. Methods About 20,961 patients who underwent primary surgical resection for stage IV colon cancer were extracted from Surveillance, Epidemiology, and End Results (SEER) Program database. Harrell's C statistic (C-index) and Akaike's Information Criterion (AIC) were used to distinguish the prognostic performance of the different LN-staging schemes. Results Of the 20,961 patients, 17,043 (81.3%) had been with lymph node metastasis, and the median number of examined lymph nodes (ELNs) was 15. When assessed as continuous values, the LODDS shown as the best system with greatest discriminatory power (C-index, 0.6241; AIC, 29114.29) generally and each subgroups divided by ELNs. When modeled as categorical cutoff variables for further clinical usage, the 8th AJCC N-stage outperformed the other three schemes with either ELNs less than 12 (C-index, 0.5770; AIC, 8992.638), between 12 and 25 (C-index, 0.6084; AIC, 13905.72), or more than 25(C-index, 0.6192; AIC, 3138.018) with increasing C-index and less AIC value. Conclusions When assessed as categorical variables, N-stage performed superiorly regardless of ELNs. When assessed as a continuous variable, LODDS exhibited good discriminative ability and goodness of fit in predicting survival for colon cancer patients regardless of ELNs.