Comparative Effectiveness of Immune Checkpoint Inhibitors in Patients with Platinum Refractory Advanced Urothelial Carcinoma

Purpose: Five programmed cell death protein 1 or its ligand (L1) inhibitors are approved for treatment of platinum refractory, locally advanced/unresectable or metastatic urothelial carcinoma. However, their comparative effectiveness is unknown. We compared time to initiation of third therapy or death, and overall survival with different programmed cell death protein 1/L1 inhibitors in patients with platinum refractory metastatic urothelial carcinoma. Materials and methods: Patient-level data were extracted from a real-world de-identified database. Comparative effectiveness was inferred via Cox proportional hazards model, weighted by matching weights. Each patient's propensity for each treatment was modeled via random forest, based on potential drivers of treatment selection. A propensity score for each therapy was used to calculate a matching weight, targeting the same estimand as 1:1 matching of treatment groups with balance among potential confounders. Eligibility criteria included diagnosis of metastatic urothelial carcinoma, receipt of first line treatment with a platinum based chemotherapy, followed by initiation of single agent programmed cell death protein 1/L1 inhibitor after disease progression from August 1, 2016 through May 1, 2019. Results: Overall, 609 patients were eligible for analysis. Median time to initiation of third therapy or death with atezolizumab, nivolumab and pembrolizumab was 4.2, 5.3 and 4.5 months, respectively, and median overall survival was 6.4, 8.0 and 8.3 months, respectively. Matching weighted analyses did not show strong evidence of differences among programmed cell death protein 1/L1 inhibitors in terms of time to initiation of third therapy or death and overall survival. Conclusions: In this large real-world cohort, effectiveness in terms of time to initiation of third therapy or death and overall survival with programmed cell death protein 1/L1 inhibitors in patients with platinum refractory locally advanced/unresectable or metastatic urothelial carcinoma was similar.