BACKGROUND: A reclassification of the International Union Against Cancer (UICC) staging system for adrenocortical carcinoma (ACC) patients has recently been proposed by the European Network for the Study of Adrenal Tumors (ENSAT) to better discriminate between cancer-specific mortality (CSM) risk strata. We formally tested the validity of the modified staging system in a large North American population-based cohort. METHODS: Kaplan-Meier survival curves depicted CSM rates in the overall population and after stratification according to the 2004 UICC or the 2008 ENSAT-staging system. Cox regression models addressing CSM tested the prognostic value of respectively the UICC or the ENSAT-staging system. Harrell's concordance index quantified the accuracy of the standard versus the modified staging system. RESULTS: In the overall population (n=573), the CSM-free survival rates at 1, 3, and 5 years were, respectively, 62.9%, 47.0%, and 38.1%. No statistically significant differences in survival were recorded between 2004 UICC stages II and III patients (p=0.1). Conversely, a statistically significant difference was observed between 2008 ENSAT stage II and stage III patients (p
