Petrylak DP, et al. - Given atezolizumab (anti–programmed death ligand 1) has demonstrated safety and activity in advanced and metastatic urothelial carcinoma, its long-term clinical outcomes in patients with metastatic urothelial carcinoma were investigated herein. With good tolerability, atezolizumab afforded durable clinical benefit to a heavily pretreated metastatic urothelial carcinoma population.

• In an expansion cohort of an ongoing, open-label, phase 1 study, patients were enrolled.
• Median follow-up of 37.8 months (range, >0.7 to 44.4 months) was carried out.
• At US and European academic medical centers, enrollment occurred between March 2013 and August 2015.
• Patients who had measurable disease per Response Evaluation Criteria in Solid Tumors version 1.1, Eastern Cooperative Oncology Group performance status 0 to 1, and a representative tumor sample, were considered as eligible.
• Evaluation of programmed death ligand 1 expression on immune cells was carried out (VENTANA SP142 assay).
• Study participants were administered atezolizumab, intravenously every 3 weeks until unacceptable toxic effects, protocol nonadherence, or loss of clinical benefit.
• Safety was primary outcome, and secondary outcomes included objective response rate, duration of response, and progression-free survival.
• In key baseline subgroups, response and overall survival were assessed.

• Data showed that 95 patients were evaluable (72 [76%] male; median age, 66 years [range, 36-89 years]).
• Atezolizumab was administered to 45 (47%), as third-line therapy or greater.
• A grade 3 to 4 treatment-related adverse event, mostly within the first treatment year, was noted in 9 patients (9%); no serious related adverse events were observed thereafter.
• A related event led 1 patient (1%) to discontinue treatment.
• Treatment-related deaths did not occur.
• In 26% (95% CI, 18%-36%) of patients, occurrence of responses was noted.
• Data showed that median duration of response was 22.1 months (range, 2.8 to >41.0 months), and median progression-free survival was 2.7 months (95% CI, 1.4-4.3 months).
• In addition, median overall survival of 10.1 months (95% CI, 7.3-17.0 months) was documented; 3-year OS rate was 27% (95% CI, 17%-36%).
• Researchers observed that response occurred in 40% (95% CI, 26%-55%; n = 40) and 11% (95% CI, 4%-25%; n = 44) of patients with programmed death ligand 1 expression of at least 5% tumor-infiltrating immune cells (IC2/3) or less than 5% (IC0/1), respectively.
• They also noted that median overall survival in patients with IC2/3 and IC0/1 was 14.6 months (95% CI, 9.0 months to not estimable) and 7.6 months (95% CI, 4.7 to 13.9 months), respectively.