Purpose: Traditional external beam radiation therapy for primary and metastatic liver tumors has necessitated complex treatment planning due to the low tolerance of normal hepatic tissue to radiation. While tumoricidal doses of radiation range between 100 -120 Gy, radiation doses from external beam therapy to normal parenchyma above 35 Gy substantially increase the risk of radiation hepatitis, characterized by elevation in alkaline phosphatase, hepatomegaly, jaundice and ascites. This is the first known description of a new and unique approach (“radiation segmentectomy”) using intra-arterially infused 90Y glass microspheres (TheraSphere®) to deliver tumoricidal doses ranging from 163 to 4993 Gy with minimal radiation exposure to normal tissue.

Materials & Methods: 18 patients (9 females), with a median age of 65 years (41-80) underwent TheraSphere®  treatment for unresectable hepatoma (n=12) or metastatic liver disease (n=6). Patients presented with good performance status (ECOG 0-1) and normal liver function tests at baseline. All patients received selective infusion of 90Y microspheres to segments within the right (n=13), left (n=4) or both (n=1) lobes. Selective pre-treatment angiographic evaluations followed by a Tc-99m MAA scan, predicted 90Y microsphere distribution. The median segmental mass treated was 231.8 gm (108-1236); median activity of 90Y infused was 1.4 GBq (0.8-3), median absorbed tumor dose was 925.9 Gy (163-4993); median dose to normal segmental parenchyma was 14.1 Gy (0.2-124). Clinical follow-up and laboratory values were obtained at 30-day intervals for up to 120 days.

Results: All patients received treatment on an outpatient basis and were discharged <6 hours after catheterization. Other than complaints of fatigue for 7-10 days following treatment, there were no clinical adverse effects. Liver function tests remained within normal limits for all patients for a median follow-up of 60 days (20-200). No patient exhibited signs or symptoms of radiation hepatitis during the follow-up period.

Conclusion: Tumoricidal radiation doses approaching 5000 Gy can be achieved to portions of the liver with virtually no adverse clinical events. Radiation segmentectomy employing selective and non-embolic infusion of 90Y microspheres to targeted hepatic segments appears safe with minimal toxicity in a patient population whose disease is refractory to other forms of treatment. This approach permits the safe delivery of extremely high-doses of radiation that cannot be achieved using traditional external beam therapy.