Tissue tolerance of normal and surgically manipulated canine liver to intraoperative radiation therapy (IORT)

Purpose : The purpose of the study is to obtain dose guidelines for the delivery of intraoperative radiotherapy to the liver of patients with colorectal liver metastases. Following partial resection of the liver, a single high dose of 10, 20, 25, and 30 Gy intraoperative radiotherapy was applied to both the resection plane as well as a nonsurgically manipulated part of the liver of 25 beagles. The temporal sequence of histological and ultrastructural changes of these irradiated parts of the liver tissue was investigated. Methods and Materials : The feasibility of delivering single large dose of intraoperative electron beam radiotherapy to the normal and partially hepatectomized liver was experimentally investigated in a canine study. Results : There were no postoperative complications, no morbidity or mortality with a minimal follow-up of 1 year. Autopsy performed 3 months following irradiation showed only mild histopathological changes. One year following intraoperative radiotherapy more distinct histopathological changes consisting of capsular thickening, diffuse parenchymal fibrosis and subcapsular hepatocellular atrophy were found. The liver function remained intact. Conclusion : This study demonstrated that intraoperative radiotherapy to part of the liver in the canine model can be safely applied and doses up to 30 Gy are well tolerated.