While radiation therapy might seem like an unrealistic option for managing horses with cancer, Janean Fidel, DVM, MS, Dipl. ACVR, Dipl. ACVIM, from Washington State University's College of Veterinary Medicine suggests the opposite. She attests that radiation therapy is a viable option for numerous equine tumors, including melanomas and sarcoids.

"Even though cancer is not as common in horses as dogs or cats, it does still occur and just like in small animals, radiation therapy is a valuable tool in the treatment of our equine oncology patients," emphasizes Fidel.

At the American College of Veterinary Internal Medicine (ACVIM) Forum, held June 4-7, Fidel reviewed the biology of radiation therapy and highlighted that the goal of this modality is to deliver the highest possible dose of radiation to the tumor while sparing the normal surrounding tissue--a challenging task at best.


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According to Fidel, "Tumors located on extremities or head are much easier to position, but any body part that fits under the beam can be treated."

One important caveat presented by Fidel was that only tumors that have not or are do not have a tendency to metastasize should be considered.

Three different forms of radiation therapy are available, each associated with pros and cons. These are brachytherapy (short distance radiation therapy), pleisotherapy or very short distance radiation therapy, and therapy at a distance, also called teletherapy, or external beam therapy.

Six American facilities currently provide radiation therapy services (one or more of the above described types) for horses including Auburn University in Alabama, the University of Missouri-Columbia's College of Veterinary Medicine, Ohio State University College of Veterinary Medicine, Texas A&M, the University of California Davis, and Washington State University. Contact information for each of these schools is provided in Fidel's ACVIM 2008 Forum abstract titled, "Radiation Therapy in Horses: Something to Consider."

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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