Clinical Validation of the Intermediate-risk Non-muscle-invasive Bladder Cancer Scoring System and Substratification Model Proposed by the International Bladder Cancer Group: A Multicenter Young Academic Urologists Urothelial Working Group Collaboration.

Background and objective: Intermediate-risk (IR) non-muscle-invasive bladder cancer (NMIBC) encompasses a broad spectrum of disease, with heterogeneous outcomes in terms of disease recurrence and progression. The International Bladder Cancer Group (IBCG) recently proposed an updated scoring model for IR substratification that is based on five key risk factors. Our aim was to provide a clinical validation of the IBCG scoring system and substratification model for IR NMIBC.

Methods: This was an international multicenter retrospective study. Patients diagnosed with IR NMIBC between 2012 and 2022 and treated with transurethral resection of the bladder and adjuvant intravesical chemotherapy were included. According to the presence or absence of risk factors, patients with IR NMIBC were further categorized in IR-low (no risk factors), IR-intermediate (1-2 risk factors), and IR-high (≥3 risk factors) groups. The 1-yr and 3-yr rates for recurrence-free survival (RFS) and progression-free survival (PFS) were evaluated for each subgroup. Cox regression analyses were used to compare oncological outcomes between the groups.

Key findings and limitations: Of the 677 patients with IR NMIBC included in the study, 231 (34%), 364 (54%), and 82 (12%) were categorized in the IR-low, IR-intermediate, and IR-high groups, respectively. There were significant differences in RFS and PFS rates between these groups.

Conclusions and clinical implications: We provide the first clinical validation of the IBCG scoring system and model for substratification of IR NMIBC.

Patient summary: Our study demonstrates that patients with intermediate-risk non-muscle-invasive bladder cancer can be correctly classified into three distinct subgroups according to their risk of both disease recurrence and progression. Our results support use of this scoring system in clinical practice.