External validation of the 8th American Joint Committee on Cancer staging system for gall bladder carcinoma

Abstract

Background: To validate the changes within the American Joint Committee on Cancer (AJCC) 8th staging system for gall bladder carcinoma compared to AJCC 7th staging system. Methods: Surveillance, Epidemiology and End Results (SEER) database [2004–2014] was queried. Kaplan-Meier survival analyses and Log-rank testing were assessed according to both AJCC 7th and 8th staging systems. Likewise, Cox cancer-specific hazard ratio was evaluated according to both staging systems. Results: Overall survival was assessed according to the two staging systems; and P values for overall trend (log/rank test) were significant (P<0.001) for both scenarios. Cox regression cancer-specific hazard adjusted for age, gender, histology, gender and surgery was evaluated according to the two staging systems. According to AJCC 7th staging system, the following pair wise hazard ratio comparisons were significant (II vs. IIIA; IIIB vs. IVA; IVA vs. IVB). According to AJCC 8th staging system, the following pair wise hazard ratio comparisons were significant (II vs. IIIA; IVA vs. IVB). C-statistic was assessed using death from gall bladder carcinoma as the dependent variable; and the findings for the two staging systems were as follows: AJCC 7th staging system: 0.684 (SE: 0.008; 95% CI: 0.667–0.701); AJCC 8th staging system: 0.682 (SE: 0.009; 95% CI: 0.665–0.698). Conclusions: There is a comparable discriminatory performance for AJCC 8th staging system compared to AJCC 7th staging system. Change form location-based to number-based N category assessment does not improve the overall prognostic performance of the staging system.