IMbrave150: Efficacy and Safety of Atezolizumab plus Bevacizumab versus Sorafenib in Patients with Barcelona Clinic Liver Cancer Stage B Unresectable Hepatocellular Carcinoma: An Exploratory Analysis of the Phase III Study.

Introduction: The phase III IMbrave150 study established atezolizumab + bevacizumab as standard of care in patients with unresectable hepatocellular carcinoma (HCC). This exploratory analysis reports efficacy and safety results in patients with baseline Barcelona Clinic Liver Cancer (BCLC) stage B disease. Methods: Patients with systemic treatment-naive unresectable HCC and Child-Pugh class A liver function were randomized 2:1 to receive 1,200 mg of atezolizumab plus 15 mg/kg of bevacizumab or 400 mg of sorafenib. Co-primary endpoints were overall survival (OS) and progression-free survival (PFS) per independent review facility (IRF)-assessed Response Evaluation Criteria in Solid Tumours (RECIST) version 1.1 in the BCLC stage B subgroup. Patients in this analysis had BCLC stage B disease at baseline per electronic case report form. Secondary efficacy endpoints included the objective response rate (ORR) and change in the sum of longest diameters (SLD) of target lesions from baseline per IRF RECIST 1.1 and modified RECIST (mRECIST) for HCC. Results: Of 501 enrolled patients, 74 (15%) had BCLC stage B disease at baseline (atezolizumab + bevacizumab, n = 49; sorafenib, n = 24). For this group, median follow-up was 19.7 months. A trend toward improved OS and PFS per IRF RECIST 1.1 was observed with atezolizumab + bevacizumab versus sorafenib (OS: hazard ratio [HR]: 0.63; 95% confidence interval [CI]: 0.29, 1.34; PFS: HR: 0.64; 95% CI: 0.36, 1.12). ORRs per IRF RECIST 1.1 and HCC mRECIST were 43% and 50% with atezolizumab + bevacizumab and 26% and 30% with sorafenib, respectively. Percentage change in SLD of target lesions from baseline per IRF RECIST 1.1 and HCC mRECIST showed durable responses with atezolizumab + bevacizumab treatment. Safety data were consistent with known profiles of atezolizumab and bevacizumab, as seen in the overall study population. Discussion/Conclusion: Efficacy benefits were observed with atezolizumab + bevacizumab in patients with baseline BCLC stage B disease, consistent with the intention-to-treat population.