Experts Detail Progress in Treating Cancer Using Advanced Intensity Modulated Radiation Therapy -- IMRT.

Business Editors/Health & Medical Writers

PALO ALTO, Calif.--(BW HealthWire)--Jan. 10, 2000

Higher Doses of Radiation Possible with IMRT Improve

Local Tumor Control; Increased Precision Can Reduce

Complications, Improve Quality of Life

High-resolution Intensity Modulated Radiation Therapy (IMRT) enables physicians to improve outcomes in cancer patients by increasing radiation doses in tumors, while avoiding nearby healthy tissue and reducing complications and improving patient comfort. These were the findings from physicians from Memorial Sloan Kettering Cancer Center, Emory University, and McGill University who presented information from their clinical experience using the new radiotherapy technique for treating prostate, pancreatic, and head and neck tumors at a recent symposium sponsored by Varian Medical Systems, Inc. (NYSE: VAR).

The presentations were made to more than 500 radiation oncologists and allied professionals at the 1999 American Society for Therapeutic Radiology and Oncology (ASTRO) annual meeting. IMRT uses real-time computer control and advanced medical linear accelerators and accessories to focus higher, "biologically effective," radiation doses on tumors, while minimizing exposure to surrounding organs and tissue.

Michael Zelefsky, M.D., associate professor of radiation oncology at Memorial Sloan-Kettering Cancer Center, New York, described a study of 171 patients with early stage prostate cancer. The study compared patients receiving conventional three-dimensional conformal therapy (3D-CRT) to those getting high-resolution IMRT treatments. Both techniques are designed to better "shape" the radiation to the tumor volume. In each group, the beam shaping techniques were used for delivering a higher dose of radiation (81 Gray (Gy).

Zelefsky and his colleagues found improved local tumor control rates (from 55 to 94 percent) as measured by favorable biopsy in the 81 Gy patients compared with those receiving lower doses of radiation (64.8 - 72 Gy). Dr. Zelefsky also observed that when either of the two techniques were used, higher doses of radiation could be used without significant urinary side effects such as incontinence or rectal bleeding. However, Dr. Zelefsky found that IMRT was more effective than 3D-CRT for minimizing dose to the rectum and surrounding healthy tissue. Additionally, the risk of rectal bleeding two years after treatment was two percent for IMRT, compared with 10 percent for conventional 3D-CRT.

According to Dr. Zelefsky, previous studies have indicated that higher doses of radiation are necessary to treat early prostate cancer. IMRT should be considered for routine use with patients who have cancer confined to their prostate, he said.

Jerome Landry, M.D., of the Department of Radiation Oncology at the Emory University School of Medicine, Atlanta, described his use of IMRT for treating pancreatic carcinoma. Dr. Landry noted that while conventional radiotherapy can improve local disease control, it can also result in an increase in small intestine toxicity.

According to Dr. Landry, IMRT technology gives physicians a way to maximize the dose to the pancreatic tumor and minimize the dose to the small intestine. As a result, the radiation dose can be increased before surgery, which should ultimately result in a higher percentage of tumors being resected surgically.

Te Vuong, M.D., of the McGill University School of Medicine, Montreal, discussed her use of IMRT for the treatment of head and neck cancers. In her remarks, Dr. Vuong noted that IMRT allows for improved beam shaping , which targets more cancer-killing energy at the tumor and less at surrounding structures. Of particular note is sparing of the parotid gland and the attendant reduction of xerostomia or "dry mouth," a frequent complication associated with head and neck radiotherapy, Dr. Vuong noted.

"With IMRT, we are witnessing a revolution in the effectiveness of radiotherapy for controlling cancer and for reducing complications," said Richard M. Levy, Ph.D., president and CEO of Varian Medical Systems. "We are proud of our role in developing radiotherapy solutions that help make such treatments possible, and in providing a forum for these leading physicians to share their experiences with colleagues. Judging by the standing-room-only audience at this seminar, IMRT is clearly at the forefront of the minds of oncology professionals, and may rapidly become the standard of care for many cancer patients."

Varian Medical Systems, Inc., (NYSE:VAR) of Palo Alto, Calif., is the world's leading manufacturer of integrated cancer therapy systems, which are treating an estimated 100,000 patients per day. The company is also the premier supplier of X-ray tubes and flat-panel digital subsystems for imaging in medical, scientific and industrial applications. Varian Medical Systems employs 2,300 people who are located at manufacturing sites in North America and Europe and in its 34 sales and support offices around the world. In its most recent fiscal year ended October 1, 1999, Varian Medical Systems reported sales of $590 million. Additional information is available at www.varian.com/vms/.