Readjustment of nodal staging by integrating tumor deposits and positive lymph nodes in patients with stage III colon cancer: a population-based analysis

Whether tumor deposits (TDs) should be classified as lymph node metastasis or distant metastasis remains controversial. To address this predicament, we conducted this study to identify the predictive value of TDs on the survival of patients diagnosed with stage III colon cancer (CC). 12,904 eligible patients diagnosed with stage III CC between 2010 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. The best cutoff point of TD quantity was determined based on the difference in survival. Cox proportional hazards model was employed to perform univariate and multivariate analyses. The Kaplan-Meier method and log-rank test were performed to calculate the differences between overall survival (OS). Our results showed that the number of TDs was a significant prognostic factor in patients with stage III CC (P < 0.0001). We added the number of TDs to the pN stage and devised a new pN stage, there were no significant differences in the survival of npN, except npN2a (P > 0.05). Upon re-staging to the same npN stage, the difference in survival between TDs+ and TDs- disappeared (P > 0.05). The median survival times for N2aTDs > 4 and N2bTDs > 4 were 33 and 37 months, respectively, which were significantly shorter than that of N2TDs- (65 months) and represented the worst survival rates among all groups. In conclusion, the number of TDs indicated a poor prognosis for patients with stage III CC. Incorporating TDs into the pN is feasible to predict prognosis.