Aims: The definition of tumour deposit (TD) in colorectal cancer (CRC) was changed recently in the American Joint Commission on Cancer (AJCC) Staging Manual, 7th edition. We aimed to examine the prognostic values of the newly defined TD and perineural invasion (PNI) in this population study.
Methods and results: We identified the incidental CRC cases with known TD or PNI status in the Surveillance, Epidemiology, and End Results (SEER) programme diagnosed in 2010 and 2011. Kaplan-Meier survival analysis and multivariable Cox proportional hazards models were used to estimate overall survivals (OS) and cancer-specific survival (CSS). We found that 6.71% (2774 of 41 323) of the CRC cases were positive for TD and 9.61% (3970 of 41 215) positive for PNI. In multivariable models, TD- and PNI-positive statuses correlated independently with worse 3-year OS [hazard ratio (HR): 1.68, 95% confidence interval (CI): 1.58-1.80 and HR: 1.24, 95%: CI: 1.16-1.32, respectively] and 3-year CSS (HR: 1.79, 95% CI: 1.65-1.94 and HR: 1.28, 95% CI: 1.18-1.38, respectively, P < 0.001 for all). Other independent prognostic factors included age, T category, N category, tumour location and tumour grade, but not gender. TD and PNI correlated with worse OS in all N categories (P < 0.001 for all). TD-associated HR for 3-year OS increases as the N category becomes lower (1.73 in N2, 2.32 in N1 and 3.24 in N0), while rare (1.4%) TD-positive CRC in N0 category should have been assigned to N1c.
Conclusions: Tumour deposit and PNI correlate independently with worse 3-year OS and CSS. TD appears prognostically more important in the CRC of lower N categories.
Keywords: colorectal cancer; perineural invasion; prognosis; racial disparity; survival; tumour deposit.
© 2016 John Wiley & Sons Ltd.