Atezolizumab in Metastatic Urothelial Carcinoma Outside Clinical Trials: Focus on Efficacy, Safety, and Response to Subsequent Therapies.

Background: Little is known about the outcomes, safety, and response to subsequent therapies of patients with metastatic urothelial carcinoma (mUC) treated with atezolizumab outside clinical trials.

Objectives: The objectives of the study include to report the clinical efficacy and safety of atezolizumab, and the response to future therapies in clinical practice outside clinical trials.

Patient And Methods: This is a retrospective, single-center study including consecutive patients with confirmed mUC who received at least one dose of atezolizumab 1200 mg every 3 weeks between May 2016 and April 2017.

Results: Seventy-nine patients, median age 72 years (range 29-93), 71% men and 76% ECOG PS 0-1, were identified. Most patients (79%) had primary cancer in the bladder, 62% had prior surgery, and 75% received at least one prior line of treatment (34 patients had prior cisplatin-based chemotherapy). Best response included 18% partial response, 29% stable disease, and 53% progressive disease. Patients were on atezolizumab for a median of 2.7 months (95%CI, 1.8-3.6) and median PFS was 3.2 months (95%CI, 1.6-4.8). A total of 33 (42%) patients had significant (any cause) AEs, including grade 4 hyperbilirubinemia in two patients; no toxic deaths were reported. At time of data analysis, only 18% of patients received at least one subsequent line of treatment for a median of 1.8 months (95%CI, 0.0-5.0) while 42% were referred to palliative care/hospice or died.

Conclusions: Patients with mUC who progressed on atezolizumab were unlikely to receive subsequent systemic treatments and the benefit of those treatments appeared limited in our cohort. The findings may impact timing and designs of clinical trials in mUC.