UF develops radiation-targeting system to treat tumors but spare healthy tissue

July 6, 2001

GAINESVILLE, Fla. – University of Florida scientists have developed new technology to more precisely target radiation beams at cancerous tumors of the body’s internal organs, an advance they hope will improve cure rates and result in fewer side effects.

The new system, now being sold commercially, employs sophisticated three-dimensional imaging and optic guidance techniques to ensure that radiation therapy is directed only at tumors – greatly minimizing any spillover into surrounding healthy tissues.

Conventional radiotherapy beams used to target tumors located anywhere but the head – such as in the prostate, breast or lung – typically include an extra margin to account for the uncertainty of a tumor’s location. This uncertainty exists primarily because Internal organs aren’t fixed in place; they can shift around slightly in relationship to a patient’s skin.

Through the new system, technicians can view up-to-the-minute 3-D ultrasound images of a tumor and receive step-by-step computer guidance in positioning the patient on the treatment table. Thus, because there is no longer uncertainty about the tumor’s position, the radiation of surrounding normal tissue can be minimized.

“There’s an assumption that the more normal tissue you can exclude from receiving radiation, the less likely you are to have complications,” said Frank J. Bova, a physicist at the Evelyn F. and William L. McKnight Brain Institute of UF who is one of the system’s inventors.

“Since we have better positioning and can avoid normal tissue, we’re also going to be trying to determine if we can improve cure rates by increasing the dose of radiation given to certain tumors and do it without getting increased side effects,” said Bova, the A.E. and B.W. Einstein professor of neurosurgery, who also is affiliated with the UF Shands Cancer Center.

UF, which has licensed the technology to Zmed Inc., has applied for a patent on the system. The California- and Massachusetts-based company is selling the product under the trade name SonArray. The U.S. Food and Drug Administration approved SonArray for marketing last year.

A clinical trial funded by a $525,000 grant from the National Cancer Institute is comparing SonArray with conventional radiation targeting in patients with prostate cancer, the No. 2 cause of cancer deaths in men in the United States. The American Cancer Society estimates there will be about 198,100 new cases of prostate cancer this year and that more than 31,000 men will die of the disease.

In the randomized trial, just beginning at the University of Iowa and Saint Barnabas Health System’s Community Medical Center in Toms River, N.J., 120 patients will be assigned to receive daily treatment for several weeks using SonArray or conventional targeting measures.

In the conventional treatment group, the tumor and a surrounding margin of 1 to 2 centimeters will be irradiated, said Dr. John Buatti a former UF faculty member who is now the University of Iowa’s director of radiation oncology. In the SonArray group, the surrounding margin will be smaller – from .2 to 1 centimeter. Both groups will receive the same radiation dose.

The groups will be evaluated to determine whether the new system reduces the incidence of adverse effects that often accompany radiation to the prostate, such as problems with bladder, bowel and sexual functioning. Dr. Joseph Lattanzi, of New Jersey, is the principal investigator for the clinical trial.

In most cancer centers today, radiation oncologists design a patient’s radiation therapy using noninvasive computed tomography (or CT) images taken in the days or hours leading up to treatment. The patient’s body is marked on the skin to indicate where the radiation should be directed. In some centers, the patient also is positioned to lie in a body mold as an extra measure to try to make sure the tumor is in the location indicated by the earlier CT scans.

“Skin marks can help you get close, but they still may be a centimeter or two off-target,” Bova said. “We know that the relationship between external skin marks and internal organs is not fixed.”

In the UF system, the treatment also is planned using CT scans, but at the actual time of therapy, the tumor’s location is again identified through a three-dimensional ultrasound scan.

“We also use a laser optic guidance system that enables us to now the exact position of the tumor in the treatment room based upon the ultrasound images.

We are able to determine where every pixel in the room is,” said Bova, who together with other UF researchers holds five patents on radiation therapy techniques.

The SonArray system was developed over the past four years at UF’s McKnight Brain Institute. A joint program between the McKnight Brain Institute and UF’s College of Veterinary Medicine for treating animals has enabled the scientists to extensively test the system while providing state-of-the-art therapy.

Earlier this year, the University of Iowa began using SonArray in one-day, high-dose radiation therapy to treat people who have tumors in certain tissues, including lung, liver and bone. Buatti said that the University of Iowa was the first in the world to perform ultrasound-guided radiosurgery on a tumor located in a place other than the head.

In addition to Bova and Buatti, other key contributors to the development of the SonArray system include Sanford Meeks, of Iowa and Dr. William A. Friedman, and Lionel G. Bouchet of UF.