Validation of non‐muscle‐invasive bladder cancer risk stratification updated in the 2021 European Association of Urology guidelines

Abstract Objective The objective of this study is to validate the predictive ability of the 2021 European Association of Urology (EAU) risk model compared to that of existing risk models, including the 2019 EAU model and risk scoring tables of the European Organization for Research and Treatment of Cancer, Club Urologico Espanol de Tratamiento Oncologico, and Japanese Nishinihon Uro‐oncology Extensive Collaboration Group. Patients and methods This retrospective multi‐institutional database study included two cohorts—3024 patients receiving intravesical bacillus Calmette–Guerin (BCG) treatment (BCG cohort) and 789 patients not receiving BCG treatment (non‐BCG cohort). The Kaplan–Meier estimate and log‐rank test were used to visualize and compare oncological survival outcomes after transurethral surgery among the risk groups. Harrell's concordance index (C‐index) was used to evaluate the predictive ability of the models. Results We observed a risk shift from the 2019 EAU risk grouping to the 2021 EAU risk grouping in a substantial number of patients. For progression, the C‐index of the 2021 EAU model was significantly higher than that of the 2019 EAU model in both the BCG (0.617 vs. 0.572; P = 0.011) and non‐BCG (0.718 vs. 0.560; P