Two cases of hepatocellular carcinoma successfully treated by carbon ion radiotherapy after atezolizumab plus bevacizumab treatment

We herein report two cases of huge hepatocellular carcinoma (HCC) that were successfully treated by carbon ion radiotherapy after atezolizumab plus bevacizumab treatment. Case 1, an 84-year-old man, was diagnosed with HCC (maximum diameter: 11 cm) with portal invasion and presented HCC rupture. After obtaining hemostasis with transcatheter embolization, three cycles of atezolizumab-bevacizumab therapy were administered, and marked shrinkage of the HCC was confirmed. However, he developed jaundice, liver damage and cerebral subcortical hemorrhage. Thus, atezolizumab-bevacizumab therapy was discontinued. Total bilirubin, transaminase levels, and physical activity improved well with prednisolone, an antihypertensive agent, and rehabilitation. Thus, treatment with carbon ion radiotherapy (CIRT) was added, and the treatment effect at 4 months after CIRT was judged as a complete response (CR) according to the modified response evaluation criteria in solid tumors (mRECIST). Case 2, a 68-year-old man, was diagnosed with HCC (maximum diameter: 14 cm). Hepatic resection was difficult because the residual liver volume after treatment would be insufficient. Five cycles of atezolizumab-bevacizumab therapy were performed, and marked shrinkage of the HCC to a maximum diameter of 9 cm was confirmed. The treatment was converted to CIRT, and atezolizumab-bevacizumab therapy resumed one month after CIRT. The treatment effect at 3 months after CIRT was judged as CR according to mRECIST. Although conversion therapy after atezolizumab-bevacizumab therapy, including surgery and radiofrequency ablation, have been reported, CIRT may be a promising new tool for conversion therapy for HCC.