Targeted Radiation To Liver Tumors Spares Tissue, Improves Quality Of Life

Selective Internal Radiation Therapy (SIRT) targets a very high radiation dose to tumors within the liver, regardless of their cell of origin, number, size or location. The procedure uses biocompatible radioactive microspheres (SIR-Spheres®) that contain yttrium-90 and emit high energy beta radiation.

"The liver doesn't tolerate external beam radiation in sufficient doses to affect tumor without damaging the remaining good liver," said Dr. C. Wright Pinson, H. William Scott Jr. Professor of Surgery and chair of the department. "These spheres emit radiation for a short distance, less than a centimeter. If you can cluster radiation right around the tumor, the radiation exposure at the tumor site compared to normal liver is favorable."

The spheres are implanted using a catheter placed in the artery feeding the liver and travel via the blood stream, where the spheres are targeted to the tumors within the liver. The spheres are trapped in the small blood vessels of the tumor (doctors do not have to identify the number or location of tumors, since the spheres target the cancerous growth in the liver) where they destroy the tumor without affecting most of the normal liver tissue.

In the procedure, an interventional radiologist selectively catheterizes the arteries feeding the tumor and monitors the catheter during administration of the dose. A nuclear medicine scan is done before the spheres are administered to assure that the catheter is correctly positioned and that the tumors will be properly targeted.

The patient stays overnight and is discharged the next day. "The early reports describe enhanced survival rate," said Pinson, who expects as many as 50 patients could be offered the therapy within the next year at VUMC.

A randomized trial in patients with colorectal liver metastases conducted by Sirtex, the manufacturer, showed the median survival rate doubled from 12.8 months with chemotherapy alone to 27.1 months with SIRT and chemotherapy. SIRT is another means of attack in the battle against liver cancer. "This is not a cure. It's a prolongation of life and an improvement of survival and quality of life," said Dr. Bill Martin, associate professor of Radiology and Radiological Sciences at Vanderbilt. However, unlike many cancer therapies, side effects are minimal.

"For the patient, it's a one-time deal and they feel relatively fine afterwards. We don't do too many procedures like that."

Many patients experience a post-procedural fever that starts immediately after implantation of the spheres and can last from a few days to a week. The fever is usually nocturnal and is likely related to the embolic effect of the microspheres and the acute radiation effects on the tumor. Some patients experience significant abdominal pain immediately after the procedure and may need pain relief with narcotic analgesia, but the pain generally subsides within an hour. Some patients will experience nausea that may require anti-emetic medication. The therapy has been used to treat hundreds of patients with liver cancer in Australia, New Zealand, Hong Kong, Singapore and Thailand. and more recently in the United States in a variety of clinical trials and in general practice.