Modifications of the AJCC 8th edition staging system for intrahepatic cholangiocarcinoma and proposal for a new staging system by incorporating serum tumor markers

Abstract Background Several studies have noted that the discriminatory ability and stratification performance of the AJCC 8th edition staging system is not entirely satisfactory. We aimed to improve the American Joint Committee on Cancer (AJCC) 8th edition staging system for intrahepatic cholangiocarcinoma (ICC). Methods A multicentric database from three Chinese mainland centers (n = 1601 patients) was used to modify the 8th edition staging system. This modified TNM (mTNM) staging system was then validated using the SEER database (n = 761 patients). A new TNM staging system, by incorporating serum tumor markers (TNMIS) into the mTNM staging system was then proposed. Results The 8th edition staging system did not provide an adequate stratification of prognosis in the Chinese multicentric cohort. The mTNM staging system offered a better discriminatory capacity in the multicentric cohort than the original 8th edition. External validation in the SEER cohort showed that the mTNM staging system also had a good stratification performance. After further incorporating a serum marker stage into the mTNM staging, the TNMIS staging system was able to stratify prognosis even better. Conclusion The proposed mTNM staging system resulted in better stratification performance and the TNMIS staging system provided even more accurate prognostic classification than the conventional TNM system.