Validation of BIAS and IBCG criteria for predicting high-grade recurrence in low-grade NMIBC eligible for active surveillance

Purpose: We evaluated the performance of two scoring systems-the Bladder Cancer Italian Active Surveillance (BIAS) criteria and the International Bladder Cancer Group (IBCG) score-for predicting high-grade (HG) disease at recurrence in patients with primary low-grade (LG) non-muscle-invasive bladder cancer eligible for active surveillance (AS). Methods: We retrospectively included patients with primary LG-NMIBC (2013-2022), eligible for AS according to BIAS criteria at time of diagnosis. All subsequent recurrences were managed with TURBT, allowing histopathological confirmation of tumor grade across 383 recurrences. Clinical data necessary to assess IBCG criteria and adherence to BIAS protocol were systematically collected at each recurrence, and their diagnostic performance in predicting HG progression was evaluated using C-statistics. Multivariable logistic regression was used to assess which individual BIAS and IBCG criteria were most predictive of progression. Results: At a median (IQR) follow-up of 55 (18-83) months, HG progression occurred in 45/383 (12%) of recurrences. BIAS criteria were met in 59% (226/383) of recurrences, of which 5.3% showed upgrading to HG. Conversely, only 16% (62/383) of recurrences had 0 IBCG risk factors, of which 8 (13%) upgraded. BIAS showed higher discriminative ability than IBCG (C-statistics 0.68 vs. 0.47, p<0.001) and higher negative predictive value (95% vs. 87%). Conclusion: In patients with primary LG-NMIBC initially eligible for AS, adherence to BIAS criteria at recurrence identifies a subgroup with a lower prevalence of HG disease at immediate TURBT and may help inform shared decision-making regarding surveillance versus immediate intervention.