Proposal Of A New T-stage Classification System For Ampullary Carcinoma Based On Tumor Size

Aim:Tumor size is regarded as a prognostic factor in currently available TNM classification staging systems for most solid tumors except for ampullary carcinoma(AC).The aim of this study was to propose a new T-stage classification system for AC to reflect the impact of tumor size on the prognostic outcome.Methods:A total of 1080 AC patients who underwent radical surgery between 2004 and 2015 were identified from the Surveillance,Epidemiology,and End Results(SEER)database.Based on the results obtained from analysis of various clinicopathologic factors,a new T-stage classification system was proposed.Results:Of the 1080 patients,618 were men and 462 were women,with a median tumor size of 2.3(0.1-12)cm.Using the 7th Edition of the AJCC Cancer Staging Manual,we noticed significant differences in overall survival(OS)between T2-T3 tumors(P<0.001)and T3-T4 tumors(P=0.002),but failed to observe significant differences between T1-T2 tumors(P=0.498)in our pair-wise comparison.Using the newly developed T-stage classification system,we were able to differentiate significant differences in OS between T1-T2 tumors(P=0.032),T2-T3 tumors(P<0.001)and T3-T4 tumor(P=0.003)in all pair-wise comparisons.The cindex for the new staging system was 0.653(95%CI,0.629-0.677),which was marginally better than 0.636 of the 7th Edition of the AJCC Cancer Staging System(95%CI,0.612-0.660).Conclusion:The new T-stage classification system described herein can better differentiate prognostic outcomes after radical resection in AC patients by incorporating tumor size and depth of tumor infiltration.