A case of hepatocellular carcinoma with "pseudoprogression" followed by complete response to atezolizumab plus bevacizumab.

Atezolizumab plus bevacizumab (Atezo + Bev) is the first immunotherapy for hepatocellular carcinoma (HCC), and in the current guidelines, it is positioned as the first-line chemotherapy for unresectable cases. Herein, we report a case of HCC with pseudoprogression followed by a complete response to Atezo + Bev. A 56 year-old man was diagnosed with intermediate-stage HCC, as defined by the Barcelona Clinic Liver Cancer system stage B. Computed tomography (CT) revealed multiple lesions in the liver without any extrahepatic lesions. First, he was treated with transcatheter arterial chemoembolization (TACE); however, multiple residual lesions were observed on CT scan 2 months after TACE. Therefore, treatment with Atezo + Bev was initiated 4 months after TACE. After the third administration of Atezo + Bev, a CT scan showed progressive disease in intrahepatic lesions, along with increased serum levels of tumor markers. Although TACE was planned again, Atezo + Bev was continued while the patient was waiting for hospitalization. After the fifth administration of Atezo + Bev, serum levels of tumor markers decreased to the normal range. Magnetic resonance imaging showed prominently reduced tumor size. Therefore, Atezo + Bev was continued, and after the eighth administration, the CT scan showed the disappearance of all the liver lesions, indicating a complete response. In immunotherapy, the therapeutic response can sometimes be obtained in an atypical pattern due to either an increase in tumor burden or the appearance of new lesions, called "pseudoprogression," which is rare in HCC.