Proposal of New TNM Staging for Stage II and III Colon Cancer Based on Cancer-Specific Survival on Population Analysis of the SEER Database

Abstract

Background: Clinically, the paradox of survival between stage IIB/C and stage III colon cancer (CC) is so evident as to be overlooked, with the consideration that local spread into adjacent structures (T4 lesions) should be upgraded to a higher stage. In this study, we aimed to examine the prognostic accuracy of American Joint Committee on Cancer 8th edition (AJCC-8) in patients diagnosed as stage II or stage III CC with curable potential. Methods: 49898 patients with CC, extracted from the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2021, were grouped into the training set, and 33161 patients from another SEER dataset between 2010 to 2015 grouped into the validation set. CC was staged by the 6th or 7th edition of the AJCC Cancer Staging system and then restaged by AJCC-8. Using a Cox proportional hazard regression model, the effects of other covariates were adjusted, and two revised Tumor-Node-Metastasis (TNM) staging systems were proposed according to the current Tumor and Node (TN) category based on cancer-specific survival (CSS). Results: SEER CC analyses showed that the right colon was a protective factor for CSS in stage II CC, but this protective role is reverse in Stage III CC. T4 was a high-risk factor with the highest hazard ratio (HR) (HR, 5.129;95% CI, 4.041–6.511;p < 0.01). Patients with T4N0M0 cancers had worse CSS than those with T3N0M0 cancers, similar to T2N2bM0 cancers. The CSS of T4bN1M0 was worse than that of T3N2bM0, but similar to that of T4N2M0. The CSS of T1-2N1M0 was similar to that of T3N0M0. The revised TNM staging showed distinctly better discrimination for T4 lesions. Conclusions: This study supports the complexity of the significance of tumour location and calls for consideration of the shift of T1-2N1M0 disease from IIIA to IIA or II and T4 lesions to stage III.