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New brain cancer treatment tested (3-7-00)

Brain cancer patients now have access to an innovative treatment that places a high dose of radiation directly into the tissue most likely to contain residual cancer cells following tumor removal.

Clinical trials are beginning at The University of Texas Health Science Center at San Antonio, one of five medical centers to test the GliaSiteTM Radiation Therapy System (RTS) developed by Proxima Therapeutics. The studies are being conducted under the guidance of the National Cancer Institute’s "New Approaches to Brain Tumor Therapy" (NABTT) program.

"The procedure may improve the therapeutic outcome for adults with malignant brain tumors," said Pamela New, M.D., assistant professor of medicine, the Health Science Center’s lead investigator on the project. "By participating in this multicenter clinical study, as an NABTT member, we continue our mission to conduct clinical evaluations of promising new treatment strategies for central nervous system malignancies."

The device is a reservoir implanted during surgery to remove a brain tumor. Soon after surgery, the reservoir is filled with liquid radiation that will disable stray cancer cells. The device is removed within three days to a week, and treatment is complete.

The procedure has the potential to improve quality of life for patients. Advantages over traditional therapies may include:

  • delivery of site-specific, internal radiation that limits exposure to healthy brain tissue;
  • the opportunity to avoid side effects associated with chemotherapy; and
  • cost that is 25 percent to 50 percent less than conventional therapies.

The American Cancer Society estimates that about 18,000 U.S. patients are diagnosed each year with malignant brain tumors, and nearly all experience tumor recurrence after initial treatment. Most tumors recur within a short period of time and more than 80 percent are located within two centimeters of the original cancer site.

Treatment depends on numerous factors, including the type, location and size of the tumor, as well as the patient’s age and general health. Surgery, followed by external beam radiation, is the traditional treatment for malignant brain tumors. Radiation therapy destroys tumor tissue that cannot be surgically removed or is used after surgery to kill remaining cancer cells.

With conventional external beam therapy, the radiation travels from the outside in, passing through healthy brain tissue first. While radiation is proven to suppress tumor recurrence, a second course of external beam treatment is rarely an option due to the unacceptable risk to healthy tissue. Treatment for recurrent tumors has been limited.

The experimental treatment combines a balloon catheter with a liquid radiation medication developed to treat patients with malignant brain tumors. During surgery, a neurosurgeon positions the balloon portion of the GliaSite catheter into the cavity created after the malignant brain tumor is removed. The other end of the catheter extends to the outside of the skull and is concealed underneath the skin at the top of the head.

When the patient recovers from surgery, the liquid solution is injected into the catheter and fills the balloon. After delivering a specified dose of radiation for three to seven days, the solution is withdrawn and the balloon catheter is removed during a brief surgical procedure.

Studies have demonstrated that survival for patients with recurrent malignant brain tumors is approximately three months without therapeutic measures, five months with surgery alone, eight months with surgery and chemotherapy, and 15 months with surgery and internal radiation.

"While it is possible to deliver additional radiation via seed implants—a process known as brachytherapy—the complexity and complications associated with this procedure have limited physicians’ use of the therapy," Dr. New said. "The GliaSite RTS is designed to overcome these obstacles so that the value of internal radiation can be made widely available to malignant brain tumor patients."

Up to 40 patients will participate in the GliaSite RTS clinical trials. All must have a recurrent, malignant brain tumor and a history of prior treatment including surgery, radiation therapy and possibly chemotherapy. The study is expected to be complete by year’s end, and Proxima is seeking U.S. Food and Drug Administration approval to market the device.

The five U.S. academic medical facilities participating in the GliaSite RTS clinical study are members of the National Cancer Institute-funded NABTT Brain Tumor Consortium. The four other institutions are the Johns Hopkins University School of Medicine (Baltimore), the Wake Forest University School of Medicine (Winston-Salem, N.C.), the Emory University School of Medicine (Atlanta) and Henry Ford Hospital (Detroit).

Contact: Myong Covert