Short- and long-term histopathological changes in the canine liver following single high-dose intraoperative radiation therapy (IORT)

Purpose: The histopathological changes in the canine liver following single high-dose intraoperative radiation therapy (IORT) were investigated in order to establish the tolerance of liver tissue to IORT, thus providing a framework for clinical IORT treatment of patients with metastatic disease to the liver. Materials and methods: Following partial resection of the liver, IORT in doses of 10, 20, 25, or 30Gy was applied to the resection plane and a non-surgically manipulated part of the liver of 25 beagles. Results: There were no postoperative complications, and no morbidity or mortality during a maximal follow-up of 5 years. Dogs were killed at 3 months, and 1, 2, 3 and 5 years following IORT. Light microscopic examination revealed capsular thickening, severe parenchymal fibrosis, liver cell atrophy, and bile duct proliferation at the irradiated area 1-2 years following IORT. At 3-5 years, however, only mild parenchymal changes were found that consisted of slight periportal fibrosis, an incidental portal-central fibrous septum and vascular changes with endothelial proliferation and focal arteriolar hyalinosis. Conclusions: This study demonstrated that following partial hepatic resection, IORT to the liver in the canine model can be applied safely, without short- or long-term treatment morbidity. Although doses up to 30Gy resulted in severe local tissue damage 1-2 years following IORT, these changes were largely reversible due to hepatic regeneration.