Tumor deposit (TD) was an important clinical characteristic associated with adverse prognosis in colorectal cancer (CRC), reported in 4.9%-41.8% CRC patients. The frequent alteration of TDs definition and category criteria in the recent 4 versions of TNM staging system make it controversial. There are several points that are not clear in the latest TNM classification regarding the coexistence of TDs and LNMs and the comparison of the prognosis value between TDs and LNMs.
Two large-scale cohorts were collected for optimally categorizing TDs with LNM in the tumor stage. The first cohort was from the SEER database involving 65,537 patients between 2011 and 2013. The second cohort was from Fudan University Shanghai Cancer Center (FUSCC) involving 2853 patients between 2010 and 2014.
TDs were observed in 6.32% of patients in SEER cohort and 14.7% in FUSCC cohort. A significantly reduced overall survival was observed for TDs in LNM positive CRC patients (hazard ratio [HR], 1.65; 95% CI, 1.54 to 1.76) in SEER cohort. Prognosis became worse as the number of LNMs increasing, but there was no significant difference in different numbers of TDs in the SEER cohort and FUSCC cohort. Therefore, whether TDs exist or not was the main point. Further analysis combining TDs with LNM shows that there is no considerable difference in the impact on overall survival between N1 and N1c, between N1 with TDs (N1TD) and N2. The 3-year survival rate was 82.3%, 72.0%, 69.9%, 55.7%, 52.1%, 39.4% for N0, N1, N1c, N1TD, N2 and N2 with TDs (N2TD) respectively in SEER cohort. Similar results were observed in the FUSCC cohort.
TD should not be considered as LNM, because they have different survival impact based on our study results. TDs and LNMs could be integrated into a modified pathological N category including 6 subtypes (N0, N1c, N1, N1TD, N2 and N2TD). Among these subtypes, the prognosis of N1c and N1 was similar which means that the revision concerning TDs in the 7th TNM staging system is adequate to predict the pN1c patients’ outcome. For the condition of TDs and LNMs coexistence, the prognosis of N1TD and N2 was similar and the prognosis of N2TD was the worst. Therefore, the modified pathological N category was reasonable solution to of apply TDs into the pN category of TNM staging system.
Clinical trial identification
Legal entity responsible for the study
Fudan University Shanghai Cancer Center
National Natural Science Foundation of China (No. 81472620) and Shanghai Science Foundation of China (No. 16ZR1406700)
All authors have declared no conflicts of interest.