Reducing complexity in International Bladder Cancer Group intermediate-risk non-muscle-invasive bladder cancer stratification: a three-factor approach

Objectives: To evaluate whether a simplified risk model preserves the prognostic performance of the International Bladder Cancer Group (IBCG) five-factor risk stratification model in intermediate-risk (IR) non-muscle-invasive bladder cancer (NMIBC). Patients and Methods: We performed a multicentre retrospective analysis of 2822 patients with IR NMIBC treated with transurethral resection of bladder tumour and intravesical therapy between 2005 and 2025. Multivariable Cox regression identified independent predictors of recurrence and progression. A simplified risk model was constructed using significant variables and compared with the full IBCG model using recurrence and progression rates, area under the curve analysis, and likelihood ratio testing. Results: A total of 2822 patients with IR NMIBC were included. When classified using the full IBCG model, 1143 (41%) were in the IR-low, 1535 (54%) IR-intermediate, and 144 (5%) IR-high-risk groups. On multivariable analysis, only multifocality, early recurrence, and failure of intravesical therapy independently predicted oncological outcomes. Using these factors, patients were stratified as IR-low (no factors), IR-intermediate (one factor), or IR-high (two or more factors). Under the simplified model, 1535 (54%) patients were classified as IR-low, 906 (32%) as IR-intermediate, and 381 (14%) as IR-high. The 3-year recurrence and progression rates increased stepwise across simplified risk groups. Discriminative performance of the simplified model was comparable to the full model across all metrics, with no meaningful loss of discrimination. Conclusion: Three variables captured the most prognostic signal in this cohort without loss of discrimination compared with the full model. This simplified model is an internally validated refinement, with planned external validation to confirm generalisability and to ensure that simplified thresholds do not alter the clinically important IR-high subgroup used in care and trials.