Radiation-induced liver disease: current understanding and future perspectives

Although radiotherapy (RT) is used for the treatment of cancers, including liver cancer, radiation-induced liver disease (RILD) has emerged as a major limitation of RT. Radiation-induced toxicities in nontumorous liver tissues are associated with the development of numerous symptoms that may limit the course of therapy or have serious chronic side effects, including late fibrosis. Although the clinical characteristics of RILD patients have been relatively well described, the understanding of RILD pathogenesis has been hampered by a lack of reliable animal models for RILD. Despite efforts to develop suitable experimental animal models for RILD, current animal models rarely present hepatic veno-occlusive disease, the pathological hallmark of human RILD patients, resulting in highly variable results in RILD-related studies. Therefore, we introduce the concept and clinical characteristics of RILD and propose a feasible explanation for RILD pathogenesis. In addition, currently available animal models of RILD are reviewed, focusing on similarities with human RILD and clues to understanding the mechanisms of RILD progression. Based on these findings from RILD research, we present potential therapeutic strategies for RILD and prospects for future RILD studies. Therefore, this review helps broaden our understanding for developing effective treatment strategies for RILD. Radiation-induced liver disease (RILD) remains poorly understood and treated because of the lack of suitable animal models. There are no effective treatments for liver cancer patients who experience this life-threatening complication of radiotherapy, partly because the precise mechanisms of disease development remain largely unknown. In a review article, Jieun Kim and Youngmi Jung from Pusan National University, South Korea, describe the insights into RILD pathology that have come from clinical observations and patient-derived tissue samples. The researchers describe existing mouse, rat, rabbit, dog and monkey models for RILD, but these animals rarely develop obstructed small veins in the liver, the hallmark symptom of the human disease. Animal models that more closely mirror human RILD, the authors argue, should reveal new insights into disease mechanisms and provide a pre-clinical platform for drug screening.