Radioactive microspheres help knock out liver tumors

For once, clogged arteries are a good thing.Physicians treating deadly liver tumors are finding success by injecting patients with radioactive microspheres that get trapped in the web of small blood vessels feeding a tumor and zap the cancerous cells. “The liver doesn’t tolerate external beam radiation in sufficient doses to affect tumor without damaging the remaining good liver,” said one physician researcher working on the treatment. “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.” From the Vanderbilt University Medical Center : New radiation therapy offers promising results at VUMC
Vanderbilt University Medical Center is the only institution in Tennessee, and one of only eight centers in the United States, offering a new radiation treatment for inoperable liver tumors.

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 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. Once trapped within the tumor, the spheres destroy the tumor, without affecting most of the normal liver tissue.

Several departments within the Medical Center collaborated to offer this innovative procedure at Vanderbilt. Pinson and Dr. Dominique Delbeke, professor of Radiology and Radiological Sciences and director of Nuclear Medicine and PET, first learned of the procedure at the International Hepatopancreatobiliary Association meeting in Japan in May, and then spearheaded bringing the procedure to Vanderbilt. Dr. R.S. Stubbs from the Wakefield Gastroenterology Center in New Zealand was presenting a lecture on SIRT, and Delbeke and Pinson invited him to come to VUMC to speak about the therapy. Stubbs presented here in September to members of Radiology, Radiation Oncology, Medical Oncology, Nuclear Medicine, and Hepatobiliary Surgery. Pinson’s first patient was then given the therapy in October.

Nuclear medicine specialist Dr. Bill Martin, associate professor of Radiology and Radiological Sciences, quickly began working on the regulations. Martin worked with Vanderbilt’s Radiation Safety department and the state of Tennessee to get SIRT included in VUMC’s nuclear license ? protocols and pricing had to be approved to get patients pre-certified.

“Bill Martin gets a big pat on the back for pushing this through. He managed to get all of this done quickly,” said Pinson.

After the paperwork was complete, the procedure had to be planned for Pinson’s patient ? a woman with metastatic colorectal cancer. After the radio-pharmacy prepared the dose, Dr. Steven Meranze, associate professor of Radiology and Radiological Sciences and director of Interventional Radiology, selectively catheterized the arteries feeding the tumor and monitored the catheter during Martin’s 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 procedure was a success and the patient went home 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.

Martin said 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,” Martin said.

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 things where we do a one-time deal and they feel fine the next day.”

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.

VUMC has now offered the therapy to three patients. Another one is expected soon.

“For decades, we’ve been trying to give targeted therapy to tumors,” Martin said. “We’re never completely successful. We’ve thought of lots of way to do it ? radiation, chemotherapy, radio-labeled antibodies that go directly to the tumor. The only truly directed procedure is surgery/ablation.

“Lots of people are looking at different ways to target a tumor without delivering toxicity to non-tumor tissues. It’s not easy. The thought with SIRT is the delivery of very high doses of radiation to hepatic tumors without significant toxicity to normal tissues.”

Meranze sees the implementation of SIRT as part of a multi-disciplinary approach to offering new treatments to patients with liver and other GI tract cancers.

“This puts Vanderbilt ahead of the curve,” Meranze said. “We are now on their (Sirtex) Web site as a place that performs the procedure. The question is: where does this fit in the treatment algorithm for patients with either primary or metastatic disease?”

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.

Other medical centers offering SIRT include Good Samaritan Regional Medical Center, Phoenix, Ariz.; Beaumont Hospital, Royal Oak, Mich.; Wake Forest University School of Medicine, Winston-Salem, N.C.; Greenebaum Cancer Center, University of Maryland, Baltimore, Md.; University of Pittsburgh Medical Center, Liver Cancer Center, Pittsburgh, Pa.; MD Anderson, Houston, Texas; and Fox Chase Cancer Center, Philadelphia, Pa.

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