Prognostic value of tumour deposit and perineural invasion status in colorectal cancer patients: a SEER ‐based population study

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.