Efficacy and Safety of Bladder Preservation Therapy in Combination with Atezolizumab and Radiation Therapy (BPT-ART) for Invasive Bladder Cancer: Interim Analysis from a Multicenter, Open-label, Prospective Phase 2 Trial

To evaluate the safety and pathologic complete response (pCR) rate of radiation therapy with atezolizumab as bladder-preserving therapy for invasive bladder cancer. A multicenter, phase 2 study was conducted with patients with clinically T2-3 or very-high-risk T1 bladder cancer who were poor candidates for or refused radical cystectomy. The interim analysis of pCR is reported as a key secondary endpoint ahead of the progression-free survival rate primary endpoint. Radiation therapy (41.4 Gy to the small pelvic field and 16.2 Gy to the whole bladder) was given in addition to 1200 mg intravenous atezolizumab every 3 weeks. After 24 treatment weeks, response was assessed after transurethral resection, and tumor programmed cell death ligand-1 (PD-L1) expression was assessed using tumor-infiltrating immune cell scores. Forty-five patients enrolled from January 2019 to May 2021 were analyzed. The most common clinical T stage was T2 (73.3%), followed by T1 (15.6%) and T3 (11.1%). Most tumors were solitary (77.8%), small (