Hepatic metastases--a physiological approach to treatment.

Hepatic metastases derived from primary malignancy of the gastrointestinal tract have a grave prognosis, with median survival rates varying from 3 to 11 months. Surgery for isolated metastases and intrahepatic artery chemotherapy are the most effective treatment options currently available. We have explored the potential use of radioactive microspheres delivered into the liver by the hepatic artery as a form of internally irradiating metastatic liver cancer. Microspheres containing radioactive Yttrium injected into the hepatic artery concentrate in the metastases rather than normal liver parenchyma, due to the fact that the blood supply of metastases is derived preferentially from the hepatic artery. Using a rabbit tumour model, radioactive microspheres delivered into the hepatic artery have been shown to lodge preferentially in tumour tissue. The therapeutic application of this phenomenon is that metastases may receive many times the radiation dose delivered to normal liver parenchyma when radioactive microspheres are delivered into the hepatic artery. This would mean that a mean dose of 30 Gy delivered to normal liver tissue would result in greater than 150 Gy being delivered to tumour tissue. Current results in experiments suggest that this form of treatment may have considerable potential for prolonging survival of patients with hepatic metastases.