Experts Detail How Advanced Imaging Technologies Are Changing The Field Of Radiation Oncology.

Business Editors/Health/Medical Writers

SALT LAKE CITY--(BUSINESS WIRE)--Oct. 22, 2003

Advances in Imaging Enable Ultra-Precise Modalities Like

Image-Guided Radiation Therapy (IGRT) And Intensity

Modulated Radiation Therapy (IMRT)

New specialized imaging techniques and intensity-modulated radiotherapy (IMRT) are enabling doctors to improve radiation treatments for many cancer patients, including children. A trio of prominent physicians described their promising observations at an "Emerging Technologies" symposium sponsored yesterday by Varian Medical Systems (NYSE:VAR) in connection with the annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO).

The physicians, Ben Slotman, M.D., Ph.D., of VU University Medical Center in Amsterdam, Suzanne Wolden, M.D., of Memorial Sloan-Kettering Cancer Center in New York, and Clifford Chao, M.D. of M.D. Anderson Cancer Center in Houston, presented information from their clinical experience with respiration-synchronized CT scanning, treating pediatric patients with IMRT, and combining PET and CT scanning for radiotherapy treatment planning.

Four-Dimensional CT Scanning

"A recent adaptation of CT scanning appears to offer a breakthrough in situations where respiration-induced tumor motion is a problem," said Dr. Slotman. The technique, referred to as "four-dimensional CT scanning," enables physicians to precisely locate a tumor at any point in the patient's breathing cycle. The information from four-dimensional CT scanning can be used to closely target a tumor during treatments in order to spare more healthy tissue.

"We can utilize the phase of respiration where the greatest separation between the tumor and a critical organ is observed," Dr. Slotman said.

According to Dr. Slotman, this technique could be applied to lung and other challenging tumors in the upper abdomen that shift as much as several centimeters with the movement of the patient's diaphragm. Normally, radiation oncologists must compensate for motion by irradiating a large margin of healthy tissue around the tumor. This limits the amount of radiation that can be delivered to the tumor, making it more difficult to eradicate the cancer.

In four-dimensional CT scanning, information about a patient's breathing pattern is captured during the acquisition of CT images . A computer system sorts, or "bins," the images based on the phase of the respiratory cycle during which they were acquired. Using these grouped images, the system can reconstruct volumetric CT images that correspond with a specific phase of the patient's respiratory cycle. Physicians can then select the best moment during the breathing cycle to activate a narrowed and more finely focused radiation beam. Since smaller amounts of normal tissue are irradiated, higher doses to the tumor, aiming at higher cure rates, can be delivered.

Combining PET and CT Images for Treatment Planning

Dr. Chao discussed the power of combining positron emission tomography (PET) and CT images during treatment planning, to generate more precise radiation delivery strategies that are carefully customized to address the specific geometric and metabolic characteristics of every tumor. "PET can provide the pathological and physiological characteristics of tumors, while CT can only show the anatomical presence of a mass," he said. "But a mass may or may not be a tumor. Even if it is a tumor, it may or may not be aggressive enough to warrant aggressive therapy."

CT scans provide anatomical data, while PET images highlight the most metabolically active parts of a tumor. By using both, doctors can see the extent of the tumor more clearly, and determine which areas are growing the fastest. This enables them to develop more precise treatment plans. According to Dr. Chao, using PET image data in addition to CT images for treatment planning has repeatedly caused him to make different treatment prescription decisions than he would have made using CT image data alone.

"Having the PET images helps with diagnosis, and it helps with treatment planning," he pointed out. "In diagnosis, we know immediately where the tumors are, and how big, and how active. Later, PET images help us design the treatment more appropriately."

Treating Pediatric Cancer With IMRT

The long-term quality of life for children who survive childhood cancer can be significantly improved thanks to image-guided modalities like IMRT, according to Dr. Wolden, who said IMRT has made a difference to children who were treated for cancer at Memorial Sloan Kettering Cancer Center.

"Many pediatric cancers require radiation therapy, but this can cause significant long-term complications," she said. For example, a pediatric brain tumor called medulloblastoma can be treated with radiation. Using IMRT can prevent severe hearing loss, which has been a common complication of treatment. With IMRT, the dose to the inner ear is minimized, and hearing can be preserved in most patients, she said.

Dr. Wolden also pointed out that IMRT treatments for tumors growing near critical bones could minimize damage so that children can grow normally. "Many who were treated for cancer in the past ended up with some cosmetic deformity, a shortened limb or some other kind of disfigurement, because radiation stopped the bone growth. With IMRT, we can often keep the dose to the bone within acceptable limits and prevent this."

In some cases, she added, IMRT can preserve vision or hormone function, or can spare normal organs like the heart, lung, and kidneys. "Pediatric tumors occur all over the body," she said. "With IMRT, all of these important normal tissues can be preserved."

"It's exciting, to see what advances in imaging are making possible in the field of radiation oncology," said Richard M. Levy, President and CEO of Varian Medical Systems, Inc., sponsor of the symposium at which these presentations were made. "At Varian, we are committed to helping clinicians learn about the latest techniques in image-guided radiation therapy. It's going to help a lot of future cancer patients, and we're proud to be part of the solution."

About Varian Medical Systems:

Varian Medical Systems, Inc., (NYSE:VAR) of Palo Alto, California is the world's leading manufacturer of integrated cancer therapy systems. The company is also a premier supplier of X-ray tubes and flat-panel digital subsystems for imaging in medical, scientific, and industrial applications. Varian Medical Systems employs approximately 2,850 people who are located at manufacturing sites in North America and Europe and in its 50 sales and support offices around the world. For more information, visit www.varian.com.