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For release after 9 a.m. CST, Tuesday, Dec. 1, 1998

NEW RADIATION THERAPY TECHNIQUE MAY IMPROVE PROSTATE CANCER SURVIVAL, REDUCE TREATMENT SIDE EFFECTS

CHICAGO -- Prostate cancer patients are benefitting from a new radiation therapy technique that decreases side effects and may lead to higher cure rates, according to research being presented here today at the 84thScientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).

In the technique, called Intensity Modulated Radiation Therapy (IMRT), the patient is immobilized and a sophisticated computer program is used to specifically pinpoint the cancer for radiation treatment without affecting the surrounding healthy tissue of the bladder and rectum. "We couldn't do this five years ago because the computer speeds weren't fast enough, but I think this will be standard practice in radiation oncology within 10 years," said E. Brian Butler, M.D., chief of radiation oncology, Baylor College of Medicine, Houston. "We've seen a significant decrease in early side effects, or toxicity, such as irritation of the bladder (burning upon urination) and irritation of the bowel (diarrhea)."

Baylor treats 50 patients daily with IMRT. The procedure is currently available at about 32 hospitals nationwide.
In the Baylor study, 50 patients were treated with IMRT. The toxicity of the procedure was compared with 30 patients treated with conventional radiation therapy techniques. Grade 2 genitourinary toxicity -- burning upon urination serious enough to require medication -- was experienced by 15 (30 percent) of the IMRT patients, compared to 13 (43 percent) of patients treated with conventional radiation therapy. Grade 2 gastrointestinal toxicity -- diarrhea serious enough to require medication -- was a problem in seven (14 percent) of the IMRT patients versus 18 (60 percent) of the conventional radiation therapy patients.

For the procedure, the patient lies in a partial box and the air is drawn out of a vacuum bag that envelopes the patient to immobilize him. The patient is imaged by computed tomography (CT) to reconstruct the bladder, rectum and prostate gland in three dimensions. The radiation therapist then directs the computer to avoid depositing radiation in the bladder and rectum and only to deliver radiation to the prostate gland. Patients are typically treated five times a week for seven weeks.

"The key is keeping the patient immobile so we can hit target areas exactly," said Dr. Butler. "Now that we can do that, we've increased radiation dosages, which should increase cure rates. However, cure rates are measured by PSA (prostate specific antigen) levels, which reach their lowest point 18 months after treatment, so we don't have results yet."

Other forms of targeted radiation therapy include stereotactic body radiosurgery and proton beam therapy. Like IMRT, stereotactic body radiosurgery includes taking extra steps to immobilize the patient, and planning therapy with a computer, but the approach is technically different. Stereotactic body radiosurgery involves using the box in which the patient lies as an external frame of reference to plan therapy. Proton beam therapy involves treating cancer with beams from protons -- elementary particles found in the nuclei of all atoms -- rather than X- rays, which are beams of electromagnetic radiation.

Prostate cancer kills more than 39,000 men a year, making it the second most common cancer killer of American men behind lung cancer, according to the American Cancer Society. The Society estimates as many as 1 million American men have been diagnosed with the disease.

Co-authors of a paper on the feasibility of IMRT being presented by Dr. Butler are: Mark Augspurger, M.D.; Bin S. Teh, M.D.; Walter H. Grant, Ph.D.; John McGary, Ph.D.; James R. Herman; and Shiao Y. Woo, M.D.

The RSNA is an association of 30,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 820 Jorie Blvd., Oak Brook, Illinois 60523-2251.

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Copies of 1998 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Nov. 30.