Applicability of the European Association of Urology 2021 Prognostic Model for Non–muscle-invasive Bladder Cancer in a Swedish Population-based Cohort

The European Association of Urology (EAU) 2021 prognostic model for non–muscle-invasive bladder cancer (NMIBC) is based on the World Health Organization (WHO) 1973 and/or WHO 2004/2022 grading systems for patients who did not receive bacillus Calmette-Guérin (BCG) instillations and is widely used to assess the risk of progression. The estimated risk of progression affects the type of adjuvant intravesical instillation (chemotherapy or BCG), with primary radical cystectomy recommended for patients with the highest risk of progression. We applied the EAU 2021 prognostic model in a population-based setting for 3392 patients with primary NMIBC diagnosed in 2013–2014 according to the BladderBaSe 2.0 database. We assessed the model calibration by comparing the 5-yr progression probability observed in our cohort with the predicted progression probability assigned for the risk groups in the original EAU study, and evaluated the discrimination according to Harrell's C index. At 5-yr follow-up, 394 patients had experienced disease progression. The progression probability observed was 4.9% (95% confidence interval [CI] 3.5–6.3%), 8.6% (95% CI 6.9–10%), 25% (95% CI 22–28%), and 23% (95% CI 14–30%) for the low-, intermediate-, high-, and very high-risk groups, respectively. The discrimination at 5 yr was 0.72 (95% CI 0.69–0.78) for the overall cohort and 0.74 (95% CI 0.70–0.80) in the group excluding the 811 patients who received BCG instillations. Showing moderate predictive ability, the EAU 2021 prognostic model has clinical utility in population-based settings despite underestimation of the observed progression risk in the low- and high-risk groups in the current study. Patient summary: We looked at how well a model predicted the risk of progression of non–muscle-invasive bladder cancer using results for a group of Swedish patients. Approximately one in four patients in the high-risk category progress to more advanced disease within 5 yr. Doctors and patients need to consider the probability of progression in the high-risk category when making shared decisions on which treatment is best for an individual patient.