Application of the International Bladder Cancer Group prediction model for recurrence-free survival on a national cohort of primary intermediate risk non-muscle invasive bladder cancer

The International Bladder Cancer Group (IBCG) has proposed a prognostic model for intermediate risk (IR) non-muscle invasive bladder cancer (NMIBC) for clinical decision-making. We applied the IBCG IR model in a population-based Swedish setting in patients with primary IR NMIBC diagnosed 2013-2014 in BladderBaSe 2.0. Patients were stratified into low-risk (unifocal and tumour size < 3 cm) and intermediate-risk (multiple and/or tumour size ≥ 3 cm) for estimation of 1- and 3-year recurrence-free survival (RFS). Among 710 patients with IR NMIBC, 329 (46%) and 381 (54%) were categorized as low- and intermediate-risk, respectively. Probabilities of disease recurrence or death at 1 and 3 years in low-risk patients were 19% (95% confidence interval [CI]: 15-23) and 41% (95% CI: 35-46), versus 27% (95% CI: 22-31) and 45% (95% CI: 40-50) in the intermediate-risk group. In a sensitivity analysis including only patients receiving serial adjuvant instillations (n = 152) the corresponding probabilities at 1 and 3 years were 19% (95% CI: 10-28) and 33% (95% CI: 22-43) versus 15% (95% CI: 7-23) and 31% (95% CI: 20-41), respectively. Thus, no clinically meaningful difference in recurrence-free survival was observed between International Bladder Cancer Group low- and intermediate-risk groups in this population-based primary non-muscle invasive bladder cancer setting.