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For Release After 10 a.m. CST, Wednesday, Dec. 3, 1997

NEW PROTON BEAM THERAPY SIGNIFICANTLY IMPROVES CANCER CONTROL

CHICAGO -- Researchers reported today that a new cancer treatment called proton beam therapy significantly increased the long-term control of some cancers compared to conventional radiation therapy, and that plans for larger trials sponsored by the National Cancer Institute (NCI) are being developed.

Clinical results with proton beam therapy conducted at Massachusetts General Hospital (MGH), the Massachusetts Eye and Ear Infirmary, the Harvard Cyclotron Laboratory, and Loma Linda University, Calif., were discussed at the 83rd Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA). Patients with locally advanced and high-grade prostate cancers and patients with skull bone sarcomas and melanoma of the eye were treated in the studies. The technique also appears to be effective in treating lung cancer and macular degeneration, a noncancerous, age-related vision problem.

Standard radiation therapy uses photon (x-ray) beams -- beams of electromagnetic radiation. In the new technique, cancer is treated with beams from protons -- elementary particles found in the nuclei of all atoms.

"Higher radiation doses can be delivered to the tumor by proton beam methods because the physical characteristics of protons mean that for many anatomic situations there can be a higher concentration of dose in the target and lesser doses to adjacent normal tissues," said Herman D. Suit, M.D., D.Phil., chief, radiation oncology, Massachusetts General Hospital, and chair, radiation oncology, Harvard Medical School at MGH, Boston. Dr. Suit delivered the Annual Oration in Radiation Oncology at the RSNA meeting.

Proton Beam Therapy for Prostate and Lung Cancer

"Conventional radiation treatments for prostate cancer often cause damage to the nearby bladder or bowel. With proton beam therapy, we can treat prostate cancer aggressively while avoiding these adverse side effects," said Carl Rossi, M.D., assistant professor, department of radiation medicine, and chief, genitourinary radiation medicine service at Loma Linda University, where the therapy is being provided. "For example, fewer than one-half of 1 percent of the patients treated with proton beams experienced incontinence as a result of the treatment, compared to 40 percent of patients who undergo surgical removal of the prostate."

According to Dr. Rossi, nearly 1,800 patients with prostate cancer have been treated with proton beams at Loma Linda University. In a study of 645 men, proton beam therapy was shown to be as effective in controlling or curing cancer as surgical removal of the prostate, at the 4-year post- treatment mark.

In the study reported by Dr. Suit, 8-year local control of cancer was achieved in 84 percent of 57 patients with advanced and high-grade prostate cancer, compared to 19 percent of patients treated with conventional photon beam therapy.

Proton beam therapy also promises to be useful in controlling early stage lung cancer. In a study of 35 patients treated at Loma Linda, the 2-year, disease-free survival from the noninvasive proton beam therapy was 85 percent -- results comparable to surgical removal of the cancer, the researchers said.

Other Treatments

In studies reported by the Massachusetts researchers, local control was achieved in 92 percent of 180 patients treated for chondrosarcoma of the base of the skull -- a cancer derived from cartilage cells -- compared to approximately 50 percent of patients treated with standard radiation therapy. Proton beams achieved local control of cancer in 45 percent of 220 patients with chordoma of the base of the skull compared to 30 percent control with standard radiation. And, in 2,100 patients with uveal melanoma -- a cancer of the eye -- local control was achieved in 96 percent and survival at 5 years is 80 percent in patients treated with proton beams -- results equivalent to surgical removal of the eye, according to Dr. Suit.

At Loma Linda, patients with macular degeneration of the "wet" type -- a proliferation of tiny blood vessels beneath the retina of the eye that is the most common cause of all legal blindness in the United States -- also were treated with proton beams. The therapy controlled the condition in nearly 90 percent of patients.

Advantages of Proton Beam Therapy

"The penetration of protons in tissue is finite and energy dependent. By appropriate selection of the distribution of proton energies, a uniform radiation dose can be delivered across the tumor while at the same time delivering zero dose to the healthy tissue on the far side of the target," Dr. Suit said. "In contrast, the photon beams, used in standard radiation therapy, lose their energy as they pass through the body, so that the dose is maximum near the surface and decreases through the entire thickness of the body," he said. "The consequence is that there is less damage to healthy tissues with proton beams for many treatment sites and the patient is able to tolerate a higher dose for many tumor sites."

Clinical trials are currently in progress at MGH and Loma Linda for cancers of the base of the skull, prostate, nasal sinus, naso- and oro-pharynx, and for benign meningiomas. "A major interest of the clinical trials will be the use of proton beams in children with solid tumors, where there is a potential for major reduction in treatment-associated side effects in the surviving patients," Dr. Suit said.

Proton beams are produced by a cyclotron or a synchrotron, a circular particle accelerator in which charged particles are propelled by an alternating electrical field in a constant magnetic field. Photon beams most commonly are produced by linear accelerators, devices in which charged electrons are propelled in a straight line by successive impulses from a series of electric fields to produce photons.

Proton beam therapy has been under investigation at MGH for cancer patients since 1974 and since 1961 for benign intra-cranial tumors using a cyclotron designed for nuclear physics research. Other sites participating in proton therapy in the United States are the University of California at Davis and the University of Indiana at Bloomington. Trials also are being planned at centers in Europe, South Africa and Japan. The clinical trials have been sponsored by NCI.

"Although the use of proton beams will require new equipment for radiation oncology centers, the incremental cost to society would be relatively small," Dr. Suit said. "The majority of the costs associated with radiation therapy is for personnel, and these costs are virtually the same for proton and x-ray treatment.

"Further, the cost of management of cancer patients includes the cost of diagnostic evaluation such as imaging studies, pathology, surgery, chemotherapy and follow-up studies. These will be independent of the type of radiation treatment."

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 2021 Spring Road, Suite 600, Oak Brook, Illinois 60523-1860.

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Copies of 1997 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Dec. 1.