A linear accelerator dedicated to treating cancers of large and small animals has recently been brought into service at the UC Davis School of Veterinary Medicine's Center for Companion Animal Health.
The first case involved a golden retriever with a mast cell tumor over her pelvis that was treated with electron therapy in January. That same week, a cat with a fibrosarcoma started treatment with photons, and a rabbit started with electron therapy. More than 30 patients have been treated on the new machine in its first three months of use. In late March, an equine patient began therapy for a squamous cell carcinoma that could not be completely removed by surgery.
Niels Pedersen, director of the Center for Companion Animal Health, explains that the radiation therapy unit will enhance oncology therapy as a stand-alone treatment or in combination with drugs and/or surgery. Dr. Pedersen states, "This new radiation therapy suite and equipment will allow us to now combine all three in the best possible ways and put us on a par with the very best cancer therapy programs, human or animal, anywhere." A linear accelerator is able to create either electrons or photons that are precisely directed at a tumor in order to kill it while sparing the surrounding normal tissue. The linear accelerator, a Varian 2100C designed for humans, cost just over $400,000 to purchase and adapt for veterinary use. The unit represents a major upgrade to equipment that the veterinary school had been using since 1997. Dr. Pedersen adds, "Another $200,000 in upgrades on the way...will greatly accelerate the speed with which animals can be treated."
The unit can deliver two different energies of photons and five different energies of electrons. Photons are ideal for deep-seated tumors while electrons are good for more superficial tumors.
Another advantage to electron therapy, according to Dr. Michael Kent, one of two radiation oncologists at UC Davis, is "We are now safely able to treat tumors over the abdomen and chest because with electrons we can largely control the depth of penetration and spare the underlying normal tissue." The Center for Companion Animal Health is the only veterinary facility in the state able to offer electron therapy.
Along with the linear accelerator, state-of-the-art software now enables clinicians to create "3-D" treatment planning. Dr. Kent reports, "We have integrated our CT scanner with the linear accelerator's treatment planning system, which allows us to very accurately pinpoint the areas that we want to treat and plan how to deliver high doses of radiation to a tumor while avoiding vital normal structures."
The cancer therapy team also uses a laser positioning system and patient positioning devices such as vacuum bags and thermoplast molds to ensure accuracy. Custom lead-alloy blocks made for each patient also protect normal tissue.
The radiation therapy department is part of the new 36,000-square-foot Center for Companion Animal Health, which houses an integrated team of medical oncologists, radiation oncologists, surgical oncologists and imaging specialists.