First clinical implementation of histotripsy for liver tumors in Japan

Histotripsy is a nonthermal therapy that mechanically disrupts and liquefies tumor tissue by generating focused microbubbles using extracorporeal ultrasound. Following U.S. Food and Drug Administration approval for the treatment of liver tumors in 2023, its clinical use has rapidly expanded. Here, we report the first clinical implementation of histotripsy in Japan, focusing on its safety and feasibility. The first treatment was performed for a 1.8-cm postoperative recurrent hepatocellular carcinoma in segment 8, followed by a second treatment for a 2.5- cm recurrent colorectal liver metastasis in segment 2 after multiple resections of intra- and extra-hepatic metastases. Histotripsy treatment times were 22 and 40 min, respectively. Target tumor coverage was confirmed by intraoperative ultrasonography, and reduced tumor enhancement was confirmed by contrast-enhanced computed tomography performed the day after treatment. The patients were discharged on postoperative days 1 and 2, respectively. No major complications occurred during follow-up to postoperative days 14 and 19, respectively, although both patients experienced mild treatment-related pain and one developed fever. These initial experiences suggest feasibility of implementing histotripsy for liver tumors in Japan.