Aristotelis Bamias, MD, PhD, of the National and Kapodistrian University of Athens, and colleagues reported on their final overall survival analysis of the phase III IMvigor130 study during the 2023 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancers Symposium (Abstract LBA441). “Atezolizumab monotherapy continued to show better tolerability versus chemotherapy with no new safety concerns,” they noted. “These exploratory data support the benefit-risk ratio of atezolizumab monotherapy versus chemotherapy for first-line cisplatin-ineligible PD-L1–high metastatic urothelial carcinoma.”

The investigators focused on patients with previously untreated, PD-L1–high, locally advanced or metastatic urothelial carcinoma. Participants were randomly assigned to receive atezolizumab monotherapy (n = 360) or placebo plus platinum chemotherapy (n = 359).

Data cutoff occurred 49 months after the last patient was randomly assigned. Although there was no apparent overall survival benefit among the intent-to-treat population, the cisplatin-ineligible, PD-L1–high subgroup demonstrated a hazard ratio of 0.56. Similar rates of overall survival at 24 months were reported in both treatment groups (32% vs. 34%). Despite participants on chemotherapy achieving a better objective response rate than those on atezolizumab (44% vs. 24%), the duration of response was short-lived (8.1 vs. 29.6 months).

Among the cisplatin-ineligible population, however, the objective response rate was slightly improved among patients on atezolizumab (40%) compared with those on chemotherapy (33%); the median duration of response was not evaluable and 6.2 months, respectively.

Most patients treated with chemotherapy had grade 3 to 4 treatment-related adverse events (80%), whereas 16% of individuals receiving atezolizumab alone reported similar events. Of note, grade 3 to 4 adverse events of special interest affected 10% and 4% of patients in the atezolizumab and chemotherapy groups, respectively.