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 ord er to establish the tolerance of liver tissue to IORT, thus providing a fra mework for clinical IORT treatment of patients with metastatic disease to t he liver. Materials and methods: Following partial resection of the liver, IORT in do ses of 10, 20, 25, or 30Gy was applied to the resection plane and a non-sur gically manipulated part of the liver of 25 beagles. Results: There were no postoperative complications, and no morbidity or mor tality during a maximal follow-up of 5 years. Dogs were killed at. 3 months , and 1, 2, 3 and 5 years folloning IORT. Light microscopic examination rev ealed capsular thickening, severe parenchymal fibrosis, liver cell atrophy, and bile duct proliferation at the irradiated area 1-2 years following IOR T. At 3-5 years, however, only mild parenchymal changes were found that:con sisted of slight periportal fibrosis, an incidental portal-central fibrous septum and vascular changes with endothelial proliferation and focal arteri olar hyalinosis. Conclusions: This study demonstrated that following partial hepatic resecti on, IORT to the liver in the canine model can be applied safely, without sh ort- or long-term treatment morbidity. Although doses up to 30Gy resulted i n severe local tissue damage 1-2 years following IORT, these changes were l argely reversible due to hepatic regeneration.