Novel concept of "sequential particle radiotherapy" with atezolizumab plus bevacizumab for hepatocellular carcinoma with portal vein tumor thrombus.

Owing to the high objective response rate of atezolizumab plus bevacizumab (Atez/Bev) for hepatocellular carcinoma (HCC), the concept of sequential conversion to local treatment has recently become mainstream. The conversion concept is mainly applied to Barcelona Clinic for Liver Cancer (BCLC) stage B cases, and radiotherapy is rarely considered as a conversion local treatment. We herein report three patients who were treated with the novel concept of "sequential particle radiotherapy," consisting of Atez/Bev therapy followed by particle radiotherapy (PRT) for HCC with advanced portal vein tumor thrombus (Vp3/4 PVTT). All patients achieved partial response radiologically and were switched to PRT. All patients were recurrence free at 1 year after the introduction of Atez/Bev therapy without any additional treatment. This upcoming combination strategy includes the advocacy of sequential concepts for BCLC stage C cases and the introduction of PRT as a local treatment after Atez/Bev.