Robot-assisted extended rectal anterior resection for peritoneal dissemination of hepatocellular carcinoma invading rectum after atezolizumab plus bevacizumab combined therapy.

The prognosis for patients with hepatocellular carcinoma (HCC) with extrahepatic metastasis remains poor. In recent years, the combination therapy of atezolizumab plus bevacizumab (ATZ/BEV) has demonstrated remarkable antitumor efficacy against HCC. Conversion surgery following chemotherapy emerges as a promising strategy for initially unresectable HCC. A 74-year-old man was referred to our department with disseminated HCC in the rectovesical pouch. He underwent hepatic subsegmental resection for primary HCC with abdominal wall invasion on the background of chronic hepatitis B 7 years ago. Intrahepatic recurrence was emerged 5 and 2 years ago, which was successfully managed with transarterial chemoembolization and radiofrequency ablation, respectively. Subsequently, 4 cm peritoneal dissemination appeared in the rectovesical pouch, invading the rectum, right pelvic neural plexus, and right seminal vesicle. ATZ/BEV therapy was initiated, but bevacizumab had to be discontinued due to fistula formation between the rectum and the tumor after two courses, and atezolizumab monotherapy was continued. After 1 year of ATZ/BEV combined therapy followed by atezolizumab monotherapy, the disseminated tumor, though still visible, exhibited a significant reduction, with no new intra- or extrahepatic lesions. To confirm the absence of other disseminated lesions, a diagnostic laparoscopy was performed. Subsequently, robot-assisted extended rectal anterior resection with the right seminal vesicle and right pelvic neural plexus, and permanent colostomy (Hartmann's procedure) were performed. Histopathological examination revealed disseminated HCC with a 4 mm resection margin to achieve R0 resection. We present a case of disseminated HCC successfully undergoing curative surgery through robot-assisted extended rectal anterior resection following ATZ/BEV combined therapy. Supplementary Information: The online version contains supplementary material available at 10.1007/s13691-024-00688-0.