PULLMAN, Wash. — A novel two-year-old marriage between the Washington State University College of Veterinary Medicine and the University of Washington School of Medicine is helping provide the pinpoint accuracy necessary to successfully treat head and neck tumors in dogs.
There’s no model when it comes to studying these tumors, nor any room for the slightest error in treatment.
Each clinical case presents very different challenges for WSU College of Veterinary Medicine cancer specialists as they probe through an anatomic minefield to take dead aim at a target that might range from one to eight centimeters in size.
The chief objective of the state-of-the-art therapy is to blast the target with radiation. But an equally high priority is to avoid damaging surrounding tissue or organs.
“This project shows what science can do when we work together,” says Pat Gavin, WSU veterinary professor and radiation oncologist. “This is literally cutting-edge technology linking human and veterinary medicine. What we’re doing for these dogs needing treatment is ahead of human medicine, but we’ll both benefit in the long run.
“We do applied research to help validate the new approach to allow this treatment to be used in humans eventually.”
Brain tumors appear in dogs with a frequency of 14.5 per 100,000 and have no breed boundaries. WSU researchers recently reviewed the records of 97 dogs with brain tumors that were presented for evaluation. Thirty-six breeds were represented.
At WSU, veterinarians have two means of treating patients. Radiosurgery, where radiation beams are directed at a small tumor sometimes only one centimeter or less in diameter. Treatment can range from one-three visits.
The other, more challenging, technique is called Intensity Modulated Radiation Therapy. It allows scientists to target a larger tumor (up to 20 centimeters, although most are six-10 centimeters) without damaging nearby tissues or the spinal column.
“But each case presents a different scenario,” says Dr. Gavin. “We have the state-of-the-art equipment here, and with cooperation from Dr. Mark Phillips and Dr. George Larramore of the Department of Radiation Oncology at the University of Washington, we are able to usually accomplish our goals.”
All cases begin with dogs suffering tumors referred to WSU by their hometown practitioners or by the owners themselves. From there, they undergo magnetic resonance imaging (MRI) and CT scans, which pinpoint the location, size and configuration of the tumor. From these, Drs. Gavin and Hege Kippenes diagnose the findings, establish dosage levels and a treatment approach. This information and the images are sent to Drs. Phillips and Larramore via the Internet. Their job is to devise an intricate battle plan based on a Prism 3D computer planning system. Prism 3D is a computer program that runs the linear accelerator — a high-energy radiation-producing machine — for each case. It enables the WSU team to irradiate the tumors, chiefly of the nasal and oral cavities, without damaging nearby tissue or the spine.
Dr. Kippenes says the objective is to deliver 100 percent radiation to the tumor and less than 50 percent to any of the surrounding tissue.
The $1.7 million state-of-the-art linear accelerator at WSU controls and directs numerous revolving radiation beams at the tumor. The challenge remains for scientists to establish identical patient positioning for each treatment, which can number as many as 18-21, spread out over three-five weeks.
To help assure accurate positioning, Dr. Gavin developed an individualized dental mold which is placed in the dog’s mouth to steady it after it is gently positioned in its own specially contoured bean-bag-type vacuum-body air cast directly beneath the linear accelerator.
While this is true science, it’s also an intricate work of art.
Rather than fully anesthetizing the patient every treatment, it is lightly anesthetized with anesthetic gas delivered by a cone-shaped mask. “The beauty of this,” says Dr. Gavin, “is that when the treatment is completed, the animal will recover in two minutes and walk out of the treatment on its own.” Typical treatments last five-10 minutes. The short-active anesthetic gas avoids organ toxicity associated with other anesthetic agents.
“We’re the only veterinary institution in the country with this equipment,” says Dr. Gavin. “But the success of this particular treatment isn’t just the result of machinery. Our team approach involving both human and animal surgeons, internists, anesthesiologists and radiologists is aimed at developing the best treatment plans for each patient.
The WSU hospital treats three to four cases monthly, while veterinary cancer specialists in the Portland and Seattle areas have four- to six-week waiting lists for patients.
Owners are grateful that once a dog is presented for its first diagnostic visit, it can be put in a relatively fast track for treatment, meaning it can often be returned in a week for its initial radiation therapy.
Treatment cost can range from $3,000-$3,500, plus travel and lodging — a mere shadow of what similar treatment would cost in a human. Some owners choose to stay in Pullman for the three-plus weeks, while others return home and phone for daily updates. Many stay at the Lucas House, a Ronald McDonald-type facility near town, which allows pets.