Dosimetry of iodine-131 ethiodol in the treatment of hepatoma.

The in vivo distribution and kinetics of [131I]Ethiodol injected through the hepatic artery have been measured on a group of four patients with hepatocellular carcinoma. The [131I]Ethiodol was distributed predominantly in the liver (70-90%) and lungs (10-20%) and was selectively concentrated and retained in the patients with massive and multinodular hepatomas with approximately 10% of the administered activity localizing in tumor. The radioactivity in the blood 2 hr postinjection was less than 0.1% and was never higher than 0.9% of the administered activity. The radioactivity cleared from normal liver tissue with an effective half-life of approximately 4 days while the clearance time from the tumor was 20-25% longer. Activity in the lungs initially increased and then cleared with a 5-day effective half-life. Based on these measurements, the estimated dose per mCi of [131I]Ethiodol administered is 31 rad to the liver, 22 rad to the lungs, 1.9 rad to the total body and 239 rad to a 4-cm diameter tumor. These results suggest that [131I]Ethiodol has the potential to deliver curative radiation doses to hepatomas with acceptable radiation burdens to normal tissues.