New radiation therapy technique developed at UF now used in treating tumors in animals

October 4, 2001

GAINESVILLE, Fla.—Through a unique partnership between University of Florida veterinarians and scientists based at the Evelyn F. and William L. McKnight Brain Institute of UF, small animals with tumors are now able to receive some of the world’s most advanced radiation planning and treatment in a procedure thought to be the first of its type available anywhere.

With the new technique, pets can be treated in one session of high-dose, precisely targeted X-ray treatment, rather than through repeated sessions over a period of weeks.

“So far we’ve done a total of 22 animals, including both dogs and cats,” said Nola Lester, a clinical instructor in radiology with the UF College of Veterinary Medicine. “About 20 of those cases have been treated over the past two years, and most have been patients with brain tumors and other tumors in the head region.”

Known as stereotactic radiosurgery, the original method has evolved as the treatment of choice for humans with certain types of intracranial tumors since its inception more than a decade ago. In 1988, Frank J. Bova and Dr. William Friedman, initiated radiosurgery treatments using their patented system known as the LINAC Scalpel. This system assists with localizing, planning and treating intracranial tumors using a specially designed adaptation of a medical linear accelerator. Recently, Bova and Friedman have developed an additional method that uses a three-dimensional ultrasound guidance system to pinpoint tumor location and target radiation beams precisely to tumors in internal organs.

“Radiosurgery has been used to treat certain brain tumors and arteriovenous malformations in people for many years,” Lester said. “We have been able to transfer this technology to animals and are using it to benefit our cancer patients.”

“As far we know, there are no other veterinary facilities in the country, and probably the world, that are doing this procedure on animals,” Lester said. “We are extremely fortunate to be in such close proximity to the Brain Institute and to have people there who are willing to collaborate with us.”

Through precision targeting, stereotactic radiosurgery allows a higher dose of radiation to be given in one session than would be administered during more traditional radiation therapy – and often with better results, Lester said.

Six years ago when she was still a puppy, Cindy was rescued from abandonment and starvation. But that wasn’t the end of the Dunnellon dog’s troubles. When she developed a tumor two years later, salvation came from a pioneering form of radiation therapy developed at the University of Florida.

With one massive but precisely targeted dose of radiation directed at the life-threatening tumor above her eye, UF veterinarians ensured that the mixed-breed dog, owned by Dorothy Schweitzer, would again prevail over adversity.

Another advantage is that animal patients receive a single dose of anesthesia rather than several that would be administered over a period of time during traditional fractionalized therapy, in which several doses of less potent radiation are given in a more general region of the area surrounding the tumor.

“Pet owners having the procedure done here need to bring their pets to the UF Veterinary Medical Teaching Hospital one time, which can be a big advantage, particularly for those who would be traveling long distances,” Lester added.

The procedure is also being used at the veterinary teaching hospital to treat vaccine-associated fibrosarcomas in cats and osteosarcomas in dogs, she said.

“In people, a stereotactic head frame was built to aid radiologists in obtaining their up-to-the-minute computer images, but we found it just didn’t work well in dogs and cats,” she said. “So we adapted a method using a ‘bite plate’ – a dental mechanism – that works much more effectively in animals.”

Lester stressed that the procedure is at times extremely effective, and at times, less so.

“In some cases, we have seen fantastic results and the tumor completely disappears. In others, this is not the case. So we are still in the early stages of figuring out what responds well and what doesn’t.”

The procedure costs approximately $2,200, roughly the same as for traditional veterinary radiation therapy. Certain animals may be eligible for a $700 UF subsidy, in addition to free follow-up care and imaging.

Dorothy Schweitzer’s dog, Cindy, though successfully treated for her eye tumor, subsequently developed an unrelated mass in her spleen, which was surgically removed at UF.

“She is really the miracle dog because she is now considerably beyond the average survival time for both of the unrelated cancers she had,” said Tim Cutler, an ophthalmology resident at the UF veterinary college who was Cindy’s initial clinician.