The Impact of Tumor Deposits on Colonic Adenocarcinoma AJCC TNM Staging and Outcome

The definition of tumor deposits (TD) in colonic adenocarcinoma has been modified in different editions of AJCC/TNM staging system. Studies have shown that the presence of TD is associated with advanced tumor growth and poor prognosis. Most of these data were obtained in patients with simultaneous lymph node (LN) metastases. Reports focusing on the impact of TD in patients without LN metastasis are limited. We retrospectively restaged all right-sided colonic adenocarcinoma over a 10-year period using criteria from the 5th, 6th, and 7th AJCC edition. We compared the number of tumor nodule interpreted as LN and TD in each edition, and evaluated the stage migration caused by TD definition change. We then assessed clinical significance of TD in AJCC 7th edition by comparing 5-year overall survival of N1c patients vs. other N category (N0, N1, N2) patients with similar T and M status. We showed that average number of tumor nodule interpreted as LN per case and number of cases with positive LN were significantly decreased with 7th edition compared to 5th/6th; however, numbers of cases with TD and <12 LN were significantly increased with 7th edition compared to 5th/6th. These changes, however, resulted in minimal effects on the final stage grouping. Our survival analysis showed that N1c patients had significantly worse survival compared to N0 patients. Although not statistically significant, the hazard ratios indicated that N1c group might have worse survival than N1 group and better survival than N2 group. Therefore, we conclude that TD predict patient outcome at least similarly to positive LN.