Protocol of the RACB study: a multicenter, single-arm, prospective study to evaluate the efficacy of resection of initially unresectable hepatocellular carcinoma with atezolizumab combined with bevacizumab

BACKGROUND: Although the standard therapy for advanced-stage hepatocellular carcinoma (HCC) is systemic chemotherapy, the combination of atezolizumab and bevacizumab (atezo + bev) with a high objective response rate may lead to conversion to resection in patients with initially unresectable HCC. This study aims to evaluate the efficacy of atezo + bev in achieving conversion surgery and prolonged progression-free survival (PFS) for initially unresectable HCC. METHODS: The RACB study is a prospective, single-arm, multicenter, phase II trial evaluating the efficacy of combination therapy with atezo + bev for conversion surgery in patients with technically and/or oncologically unresectable HCC. The main eligibility criteria are as follows: (1) unresectable HCC without a history of systemic chemotherapy, (2) at least one target lesion based on RECIST ver. 1.1, and (3) a Child‒Pugh score of 5–6. The definition of unresectable tumors in this study includes macroscopic vascular invasion and/or extrahepatic metastasis and massive distribution of intrahepatic tumors. Patients will be treated with atezolizumab (1200 mg/body weight) and bevacizumab (15 mg/kg) every 3 weeks. If the patient is considered resectable on radiological assessment 12 weeks after initial chemotherapy, the patient will be treated with atezolizumab monotherapy 3 weeks after combination chemotherapy followed by surgery 3 weeks after atezolizumab monotherapy. If the patient is considered unresectable, the patient will continue with atezo + bev and undergo a radiological assessment every 9 weeks until resectable or until disease progression. The primary endpoint is PFS, and the secondary endpoints are the overall response rate, overall survival, resection rate, curative resection rate, on-protocol resection rate, and ICG retention rate at 15 min after atezo + bev therapy. The assessments of safety and quality of life during the treatment course will also be evaluated. The number of patients has been set at 50 based on the threshold and the expected PFS rate at 6 months after enrollment of 40% and 60%, respectively, with a one-sided alpha error of 0.05 and power of 0.80. The enrollment and follow-up periods will be 2 and 1.5 years, respectively. DISCUSSION: This study will elucidate the efficacy of conversion surgery with atezo + bev for initially unresectable HCC. In addition, the conversion rate, safety and quality of life during the treatment course will also be demonstrated. TRIAL REGISTRATION: This study is registered in the Japan Registry of Clinical Trials (jRCTs051210148, January 7, 2022).