Study Overview
Objective. To evaluate the efficacy of maintenance avelumab in patients with advanced urothelial carcinoma who had received first-line platinum-based chemotherapy.
Design. International, open-label, randomized, phase 3 trial.
Intervention. Patients were randomized in a 1:1 ratio to receive either maintenance therapy with avelumab 10 mg/kg plus best supportive care (BSC) or BSC alone, per local practice. Randomization was stratified according to best response to first-line chemotherapy and metastatic site (visceral vs nonvisceral). Treatment was continued until progression, unacceptable toxicities, or patient withdrawal occurred.
Setting and participants. A total of 700 patients were enrolled at 197 sites (350 in the avelumab group and 350 in the BSC group). All patients had histologically confirmed unresectable or metastatic urothelial carcinoma. Patients received 4 to 6 cycles of chemotherapy with either gemcitabine plus cisplatin or carboplatin and had no evidence of progression after completion. Patients had a treatment-free interval of 4 to 10 weeks prior to starting maintenance therapy. Patients who received neoadjuvant or adjuvant platinum-based therapy within the prior 12 months were excluded.
Main outcome measures. The primary endpoint was overall survival (OS) assessed in both the overall population and PD-L1–positive population. Secondary endpoints included progression-free survival (PFS), objective response, time to response, duration of response, and disease control. PD-L1 expression was determined via the Ventana PD-L1 assay (SP263), and patients were classified as PD-L1 positive if they met 1 of the following: (1) at least 25% of tumor cells were positive for PD-L1; (2) at least 25% of immune cells were positive for PD-L1 if more than 1% of the tumor area contained immune cells; and (3) 100% of immune cells stained for PD-L1 if no more than 1% of the tumor area contained immune cells.
Results. The baseline characteristics were well balanced between the groups. A total of 51.1% of patients had PD-L1–positive tumors (57.6% in the avelumab group and 56.3% in the control group). At the time of analysis, 24% of patients in the avelumab group were still receiving therapy compared with only 7% in the BSC group. The most common reason for discontinuation of therapy was disease progression; 43.7% of patients in the control group received anti-PD-1 or anti-PD-L1 therapy at progression. The median follow-up was 19 months. OS at 1 year was 71.3% in the avelumab group and 58.4% in the control group. The median OS was 21.4 months in the avelumab group compared with 14.3 months in the control group (hazard ratio [HR] for death, 0.69; confidence interval [CI], 0.56-0.86, P = 0.001). In the PD-L1–positive population, OS was also significantly longer in the avelumab group (NE vs 17.1 months, HR, 0.56; CI, 0.40-0.79; P < 0.001). In the PD-L1–negative population, median OS was 18.8 months in the avelumab group versus 13.7 months in the control group (HR, 0.85). PFS was longer in the avelumab group than in the control group, with a median PFS of 3.7 months versus 2 months, respectively. The median PFS was 5.7 months in the avelumab group and 2.1 months in the control group in the PD-L1–positive population.
Adverse events (AEs) of any grade occurred in 98% of patients in the avelumab group and 77% in the control group. Grade 3 or higher AEs occurred in 47.4% of patients in the avelumab group. AEs led to discontinuation in 11.9% of patients in the avelumab group. Two patients died in the avelumab group as a result of toxicity (urinary tract infection with sepsis and ischemic stroke). Immune-related adverse events occurred in 29.4% of patients in the avelumab group. Of those, 7% were grade 3 in nature, and there were no grade 4 or 5 immune-related AEs. The most commonly seen immune-related AEs were thyroid disorders.