Abstract
PURPOSE: The evolving treatment landscape of muscle-invasive bladder cancer (MIBC) increasingly warrants novel trial design to evaluate perioperative strategies aimed at bladder preservation. To establish standardized outcome measures for evaluating organ preservation strategies in MIBC, the International Bladder Cancer Group (IBCG) and the Global Society of Rare Genitourinary Tumors (GSRGT) assembled an international, multidisciplinary consensus panel. METHODS: The IBCG and GSRGT gathered global bladder cancer experts and patient advocates to establish a framework for risk-adapted bladder-sparing treatment approaches for MIBC. Working groups reviewed the literature and developed draft recommendations, which were discussed at a live meeting in December 2024 in Milan. This was followed by voting by the members using a modified Delphi process. Recommendations achieving ≥75% agreement during the meeting were further refined and presented. RESULTS: Clinical complete response (cCR) definition should encompass the absence of high-grade malignancy on pathology and malignant cells on urine cytology and no evidence of local or metastatic disease on cross-sectional imaging. Although cCR remains immature as a primary or coprimary end point in registrational trials, it could serve as a suitable end point in early-phase studies and risk-adapted investigations. Event-free survival (EFS) remains the preferred primary end point as it could reliably capture the durability of clinically meaningful benefit after omittance of surgical consolidation or chemoradiation. Given the composite nature of EFS, events should be prespecified, evaluated in an intention-to-treat approach, and meticulously collected. Continuous assessment of individual patient preferences should begin at the outset of perioperative therapy discussions, with informed decision making prioritized throughout. CONCLUSION: The consensus definition of cCR and the framework presented in this study can serve as a foundation for thorough testing of risk-adapted bladder-sparing treatment paradigms for MIBC.