Advanced and emerging radiation therapy approaches for intrahepatic cholangiocarcinoma

Radiotherapy (RT) is an integral component of the multidisciplinary care for intrahepatic cholangiocarcinoma (iCCA). Over the past decades, RT techniques have been developed with the aim of enhancing tumor control and minimizing toxicity. The most recent technological advancements include proton beam therapy (PBT) and magnetic resonance-guided radiotherapy (MRgRT). PBT is notable for its unique physical characteristics that allow for greater sparing of surrounding normal organs, especially the liver, from low to moderate doses of radiation. MRgRT provides advantages in other aspects, including superior tumor visualization before treatment, on-board treatment plan adaptation, and tumor tracking during treatment. These features allow for precise dose delivery and safe dose escalation, especially for patients with tumors close to luminal GI structures. In this review article, the rationale, clinical outcomes, clinical applications, challenges, and future directions of PBT and MRgRT are discussed. Additionally, the potential combination of novel therapeutics with RT in iCCA is explored.