Impact of Prior Chemotherapy on Response to Second-line Pembrolizumab in Urothelial Cancer: Exploratory Analysis of the Phase 3 KEYNOTE-045 Trial.

BACKGROUND AND OBJECTIVE: Until recently, the standard first-line treatment for advanced urothelial carcinoma (UC) was platinum-based combination chemotherapy followed by avelumab maintenance therapy for patients without progressive disease (PD). For patients with advanced UC who experience PD or recurrence, standard-of-care treatment is pembrolizumab monotherapy based on the phase 3 KEYNOTE-045 study. This post hoc analysis of the KEYNOTE-045 study evaluated the efficacy of pembrolizumab compared with chemotherapy by the best response to prior platinum-based chemotherapy.

METHODS: Patients with advanced UC that progressed or recurred after first-line platinum-based chemotherapy were randomly assigned 1:1 to receive either pembrolizumab 200 mg every 3 wk (Q3W) for ≤2 yr or investigator's choice of chemotherapy (paclitaxel [175 mg/m2 ], docetaxel [75 mg/m2 ], or vinflunine [320 mg/m2 ], each Q3W). Endpoints included overall survival (OS) from the initiation of the last treatment prior to death, objective response rate (ORR), and duration of response (DOR) as per Response Evaluation Criteria in Solid Tumors version 1.1 from the date of the first response.

KEY FINDINGS AND LIMITATIONS: An objective response to pembrolizumab was observed in all groups in terms of a prior response to first-line platinum-based chemotherapy. Median OS, ORR, and median DOR were numerically greater with pembrolizumab than with chemotherapy across subgroups. Patients with PD as the best response to prior platinum-based chemotherapy had the poorest OS outcomes. Limitations include a lack of formal hypothesis testing.

CONCLUSIONS AND CLINICAL IMPLICATIONS: When compared with chemotherapy, prolonged OS and durable responses to second-line pembrolizumab were observed independently of the response to or type of prior platinum-based chemotherapy. These findings further support pembrolizumab as second-line treatment for advanced UC.