Neoadjuvant Atezolizumab Boosts Survival Rates in Patients With MIBC

New data from a phase II trial presented at the 2024 American Society of Clinical Oncology Genitourinary Cancers Symposium demonstrated the beneficial effects of neoadjuvant atezolizumab for patients with muscle-invasive bladder cancer (MIBC).

As patients with MIBC who are ineligible for treatment with cisplatin-based chemotherapy have no current standard of care options, Vadim Koshkin, MD, and colleagues tested dose escalation of neoadjuvant atezolizumab prior to radical cystectomy (RC).

The single-arm trial recruited 22 patients with cisplatin-ineligible MIBC who were eligible for RC. Each patient was administered either 1 (n=6), 2 (n=6), or 3 (n=11) cycles of atezolizumab at 1200 mg intravenously every 3 weeks.

The primary endpoint was pathologic complete response (PCR), while secondary endpoints included rate of pathologic downstaging (≤T1N0), 2-year recurrence-free survival (RFS), overall survival (OS), and biomarker assessments of pre- and post-treatment biopsies.

Given reasons for cisplatin ineligibility in the patient cohort included renal impairment (37%), hearing loss (27%), or neuropathy (9%), while the remainder declined cisplatin (27%). Upon enrollment in the trial, cT2/T3/T4 rates were 77%, 14%, and 9%, respectively, while 9% were cLN+.

PCR occurred in 14% of patients (3/22) who had received either 1 or 2 cycles of atezolizumab. Pathologic downstaging occurred in 23% of patients (5/22) at all 3 dose levels. Adjuvant atezolizumab was administered to 8 patients, while 4 patients received adjuvant therapy with cisplatin (n=3) or nivolumab (n=1) outside of the study.

Median RFS and OS were not reached after a median follow-up of 51.4 months. The 2-year RFS and OS rates were 77% and 90%. In 13 patients with available paired pre- and post-treatment samples, there was a significant increase in T-cell numbers after atezolizumab treatment. All T-cell populations were significantly more abundant in tumor tissue than in adjacent normal tissue post-treatment.

For cisplatin-ineligible patients with MIBC, treatment with neoadjuvant atezolizumab can provide durable long-term survival rates, comparable to previous data with immunotherapy-based treatment regimens.