The unique prognostic characteristics of tumor deposits in colorectal cancer patients.

Background: Both AJCC 7th and 8th TNM systems have included tumor deposits (TDs) in nodal staging when lymph nodes metastases (LNMs) are negative in colorectal cancer (CRC). However, the prognostic role of TDs has not been determined in the presence of positive LNMs. Methods: Two independent large-scale cohorts of CRC patients from the Surveillance Epidemiology and End Results (SEER) database (n=69,178) [2010-2013] and Fudan University Shanghai Cancer Center (FUSCC) (n=3,137) [2010-2014] were retrospectively analyzed. Kaplan-Meier method was used to estimate survival curves and univariate and multivariate analyses were performed by Cox proportional hazard model. Results: TDs were observed in 12.3% (n=8,480) and 14.8% (n=463) of patients in the SEER and FUSCC cohorts, respectively. Multivariate analysis suggested TDs were an independent adverse prognostic factors for overall survival (OS) (P<0.001). Remarkably, both cohorts showed the presence of TDs was significantly associated with OS, but not was the number of TDs (P=0.982 and P=0.252 for the SEER and FUSCC cohorts, respectively). In the presence of LNMs, positive TDs were associated with a shorter OS [hazard ratio (HR): 2.69, 95.0% confidence interval (CI): 2.597-2.778; P<0.001]. Further analysis combining TDs with LNMs demonstrated that the prognosis of patients with N1TD (N1 with positive TDs) was same as the N2 patients, and N2TD (N2 with positive TDs) patients had much worse prognosis than N2 (P<0.001). Conclusions: Our results have shown the unique features of TDs in patients with CRC, different from LNMs. In the presence of LNMs, TDs should also be considered in TMN system.