Focal hepatic ablation using interstitial photon radiation energy

Background: Intratumoral ablative therapy is being used increasingly for th e treatment of primary and secondary hepatic malignancies. The interstitial point-source photon radiosurgery system (PRS) is a novel ablative techniqu e that uses radiation therapy similar in dosimetry to interstitial brachyth erapy. Study Design: To determine the feasibility, toxicity, and local tissue dest ructive capabilities of the PRS in the liver, preliminary studies in a nont umor-bearing canine model were examined. A 6-month survival study was condu cted. Each animal received three radiation treatments, in the right, centra l, and left hepatic regions. Three Low-dose treatments were delivered to ea ch of six animals (group A), generating a 2.0-cm-diameter radiated sphere w ith a dose of 20 Gy at the lesion edge. Three high-dose treatments were del ivered to each of six animals (group B), generating a 3.0-cm-diameter radia ted sphere with 20 Gy at the lesion edge. Results: The treatment reproducibly generated sharply demarcated hepatic ab lative Lesions proportional to the administered dose. Mean lesion diameter at 1 month was 1.6 +/- 0.2 cm in group A and 3.4 +/- 1.0 cm in group B. Les ion size was independent of intrahepatic location, including near vascular structures. PRS therapy, when applied to portal structures, resulted in hil ar damage. Hilar damage appeared to be associated with arteriolar thrombosi s and bile duct injury. Treatment of regions adjacent to large hepatic vein s and the IVC was not associated with vessel thrombosis or stricture. Conclusions: PRS ablation is a generally well-tolerated method that results in consistent, well-demarcated, symmetric lesions of complete necrosis wit h minimal adjacent parenchymal injury. Application of such an approach for the treatment of liver tumors is promising. (J Am Coll Surg 2000;192:164-17 4. (C) 2000 by the American College of Surgeons).