Selective internal radiation therapy（SIRT）の現状と製品概要

Current status and products overview of SIRT

selective internal radiation therapy（SIRT）は，yttrium-90（⁹⁰Y）やholmium-166（¹⁶⁶Ho）などの放射性マイクロスフィアを肝動脈に投与し，肝腫瘍に対して内部から局所的に高線量の放射線を照射する選択的治療法である。本治療法は，肝細胞癌および大腸癌肝転移症例において，肝動脈化学塞栓療法（transcatheter arterial chemoembolization：TACE）や化学療法の代替あるいは補完的選択肢として，近年その有用性が注目されている。

Selective internal radiation therapy（SIRT）is an advanced treatment for liver tumors that utilizes radioactive microspheres, such as yttrium-90, delivered via the hepatic artery. Its effectiveness has been demonstrated in patients with hepatocellular carcinoma and liver metastases from colorectal cancer. Although SIRT has been in clinical use in many countries since the 2000s, its introduction in Japan was significantly delayed due to regulatory barriers under the Medical Care Act and the Radioisotope（RI）Act. However, recent legal reforms in 2025 have enabled the clinical development of SIRT in Japan, including the use of Tc-99m MAA for pre-treatment lung shunt assessment. Accurate evaluation of the lung shunt fraction and tumor absorbed dose is essential to ensure the safety and efficacy of SIRT. With these regulatory improvements and Japan’s advanced catheter technology, SIRT is expected to become an important treatment option for patients with liver cancer.