Effectiveness of First-line Immune Checkpoint Blockade Versus Carboplatin-based Chemotherapy for Metastatic Urothelial Cancer

Background: Limited data compare first-line carboplatin-based chemotherapy and immune checkpoint blockade in cisplatin-ineligible metastatic urothelial carcinoma (mUC) patients. The primary evidence guiding treatment decisions was a recent Food and Drug Administration/European Medicines Agency safety alert based on emerging data from two ongoing phase III trials, reporting shorter survival in programmed death-ligand 1 (PD-L1)-negative patients receiving immunotherapy. Final results from these trials are unknown. Objective: To compare survival in cisplatin-ineligible mUC patients receiving first-line immunotherapy versus those receiving carboplatin-based chemotherapy. Design, setting, and participants: We conducted a retrospective cohort study of 2017 mUC patients receiving first-line carboplatin-based chemotherapy (n = 1530) or immunotherapy (n = 487) from January 1, 2011 to May 18, 2018 using the Flatiron Health electronic health record–derived database. Outcome measurements and statistical analysis: The primary outcomes were overall survival (OS), comparing 12- and 36-mo OS, and hazard ratios before and after 12 mo. Propensity score–based inverse probability of treatment weighting (IPTW) was used to address confounding in Kaplan-Meier and Cox regression model estimates of comparative effectiveness. Results and limitations: IPTW-adjusted OS rates in the immunotherapy group were lower at 12 mo (39.6% [95% confidence interval {CI} 34.0–45.3%] vs 46.1% [95% CI 43.4–48.8%]) but higher at 36 mo (28.3% [95% CI 21.8–34.7%] vs 13.3% [95% CI 11.1–15.5%]) relative to the chemotherapy group. Immunotherapy treatment demonstrated inferior OS during the first 12 mo relative to carboplatin-based chemotherapy (IPTW-adjusted hazard ratio [HR] 1.37, 95% CI 1.15–1.62), but superior OS beyond 12 mo (IPTW-adjusted HR 0.50, 95% CI 0.30–0.85). Limitations include retrospective design and potential unmeasured confounding. Conclusions: In the setting of mUC, clinicians and patients should carefully consider how to balance the short-term benefit of chemotherapy against the long-term benefit of immunotherapy. Patient summary: To determine the optimal first-line therapy for metastatic bladder cancer patients who are unfit for cisplatin, we compared carboplatin-based chemotherapy versus immunotherapy using real-world data. Survival in the 1st year of treatment was lower with immunotherapy relative to chemotherapy, but for patients surviving beyond the 1st year, immunotherapy was superior.