Analyzing Efficacy, Safety of Atezolizumab, Radiotherapy for Patients With MIBC

In patients with bladder cancer, combined-modality treatment (CMT) often serves as a possible bladder-preserving option for those who are ineligible for radical cystectomy. Radiotherapy (RT) in combination with anti–PD-1 or PD-1 therapies has shown promise in improving efficacy with acceptable toxicity levels.

Research from Ovidio Fernandez Calvo, MD, and colleagues presented at the 2024 American Society of Clinical Oncology Annual Meeting sought to determine the efficacy and safety of atezolizumab plus external beam RT (EBRT) for patients with muscle invasive bladder cancer (MIBC) as a bladder preservation therapy.

In the open, phase 2 trial, patients received 6 doses of atezolizumab 1200 mg starting on day 1 of EBRT treatment as well as 60 Gy of RT in 30 fractions across 6 weeks at 2 Gy per day. The study’s primary end point was pathological complete response (pCR).

Among the 39 evaluable patients, 23 (71.9%) underwent transurethral resection. Of the 26 patients with pathological assessment upon safety visit, all reached pCR, while none received cystectomy.

Across all participants, 37 (94.9%) patients reported adverse events (AEs), with the most common being asthenia (n=21) and diarrhea (n=17). Twenty-three (59.0%) patients experienced grade 1 AEs, while 13 (33.3%) reported grade 3 AEs.

Researchers reported that 24 (61.5%) patients sustained AEs associated with EBRT, with 1 reporting a serious AE (SAE). Twenty-one (53.8%) patients demonstrated AEs connected with atezolizumab, and 3 (7.7%) experienced at least 1 SAE.

“Interim results suggest that atezolizumab combined with EBRT seems to be effective in achieving pCR in a vulnerable elderly population with multiple comorbidities,” investigators wrote. “The safety profile appears manageable. The final analysis of this study will provide valuable insights into the effect of atezolizumab with EBRT on clinical outcomes, such as survival, in addition to updated safety data.”