Atezolizumab Has Some Benefits in Urothelial Carcinoma, But OS Not Improved
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Atezolizumab does not improve overall survival (OS) compared with chemotherapy among patients with metastatic urothelial carcinoma that overexpresses PD-L1 (IC2/3) and is platinum-refractory, according to a study published in The Lancet.
For the open label IMvigor211 phase 3 study, researchers randomly assigned 931 patients with metastatic urothelial carcinoma who failed platinum-based chemotherapy to receive atezolizumab 1200 mg or physician's choice of IV chemotherapy (vinflunine 320 mg/m2, paclitaxel 175 mg/m2, or docetaxel 75 mg/m2) every 3 weeks. Tumor imaging was performed at baseline and every 9 weeks thereafter. Median follow-up was 17.3 months.
Median OS was not significantly different between the 2 study arms: 11.1 months in the atezolizumab arm vs 10.6 months in chemotherapy arm (stratified hazard ratio [HR], 0.87; 95% CI, 0.63-1.21; P =.41). This finding stopped any further investigation and rendered any additional analysis as exploratory in nature.
Objective response rates were 23% and 22% in the atezolizumab arm and the chemotherapy arm, respectively, but the duration of response was longer in the experimental arm (median 15.9 months [95% CI, 10.4-not evaluable]) compared with the chemotherapy arm (median 8.3 months [95% CI, 5.6-13.2]) (HR, 0.57; 95% CI, 0.26-1.26).
The safety profile was more favorable in the experimental arm: approximately 20% of patients receiving atezolizumab reported grade 3 to 4 adverse events compared with 43% of patients receiving chemotherapy. In addition, fewer patients in the atezolizumab arm discontinued therapy due to adverse events (7% vs 18% in the chemotherapy arm).
Although atezolizumab was associated with fewer adverse events, there was no positive impact on survival outcomes.
Powles T, Duran I, van der Heijden MS, et al. Atezolizumab versus chemotherapy in patients with platinum-treated locally advanced or metastatic urothelial carcinoma (IMvigor211): a multicentre, open-label, phase 3 randomised controlled trial [published online December 18, 2017]. Lancet. doi: 10.1016/S0140-6736(17)33297-X