The University of Georgia College of Veterinary Medicine

Oncology (Cancer) Service

Radiation Therapy (RT)

The goal of the oncology service at the University of Georgia College of Veterinary Medicine is to provide your cat or dog with the most effective cancer treatment options and to maintain the best quality of life possible.

We currently do not offer radiation therapy at the Teaching Hospital.

Download the Radiation Therapy Client/Patient Handout [PDF]

Indications for Definitive Radiation Therapy in Dogs and Cats

Depending on the type of cancer that your pet has been diagnosed with, definitive radiation therapy may be recommended either alone or in combination with other therapies (such as surgery and chemotherapy). The following list highlights some of the more common cancers that are treated with radiation therapy. For further details regarding radiation therapy, please refer to the additional information provided.

Acanthomatous epulis
Anal sac adenocarcinoma
Brain and spinal tumors
Injection site sarcomas (feline)
Mast cell tumor
Nasal tumors
Oral malignant melanoma
Salivary carcinomas
Skin carcinomas
Soft tissue sarcomas (canine)
Thyroid carcinoma

Types of RT

Pets are treated with cobalt radiation therapy. In this photo, a beam of radiation is aimed at the tumor. Dr. Royce Roberts (right) positions a patient for radiation therapy while technician Tim Jarrett (left) monitors anesthesia. The treatment is not painful, but anesthesia is required to keep the patient properly positioned for the treatment. Each treatment takes approximately 15-20 minutes.

The radiation damages DNA in the tumor's cells. The tumor cells do not die instantly, but over a period of days to months. During therapy, radiation patients must lie perfectly still. In veterinary patients, this means that they must be anesthetized. Anesthesia of radiation therapy patients at UGA is supervised by a veterinary anesthesiologist.

Prior to beginning radiation therapy, your pet will undergo diagnostic tests to determine the extent of the cancer. This important information is used to plan the best overall course of therapy for your pet and to plan the delivery of the radiation to maximize efficacy while minimizing toxicity. Radiation therapy will not begin on the same day as your initial appointment at the teaching hospital.

Radiation Therapy Treatment Schedule

Most patients are treated with a definitive protocol to achieve the best possible control of the tumor. Definitive radiation protocols typically involve daily treatments, Monday through Friday, for three to four weeks, depending on the type of tumor. The oncologist will be happy to discuss the optimal treatment plan for your pet.

Some patients are treated with a palliative protocol to relieve pain or discomfort. These patients are treated weekly for one week or once, then one week later, and then 2 weeks after the second treatment (a total of 3 treatments on a day 0, 7, 21 schedule).

Potential adverse side effects

Dogs and cats do not experience the fatigue experienced by human radiation patients. For patients treated with definitive radiation therapy, acute side effects generally start during the second half of therapy and get worse for 1 or 2 weeks after therapy is completed.

Cats generally experience mild acute side effects compared to dogs. These effects will heal by about 1 month after finishing radiation therapy and depend on the area being radiated. The clinician caring for your pet will tell you which of the following effects you should expect. This page does not describe every possible complication of radiation therapy. Please ask the oncologist if you have questions about other possible complications.

Skin: Similar to sunburn, skin will turn pink and then red. Skin can peel and ooze, then will scab over and heal. If a foot is radiated, the surface of the pads will peel off and radiated toenails may fall off. In areas where the skin rubs (like armpit or groin) or on feet, this may be uncomfortable. As the skin heals, it will be itchy. We will use anti-inflammatory drugs, antibiotics, and pain medications as needed to keep your pet comfortable and help this area to heal. We may recommend an ointment to help healing. It is extremely important that your pet does not scratch or chew the treatment area as this can result in permanent damage. We will provide an Elizabethan collar (E-collar) to prevent injury to the radiated skin.

Mouth: The lining of the mouth, gums, and tongue will become reddened and can peel. You might notice drooling and some difficulty eating. Most dogs will eat despite radiation toxicity to the mouth, but may do better with soft foods (canned food or dry food soaked in water) or even a gruel of canned food and water. It is important to change food over a few days to avoid diarrhea. We will discuss necessary diet changes with you during the course of treatment. We will use three anti-inflammatory drugs, antibiotics, and pain medications as need to keep your pet comfortable and help this area to heal. We may recommend a special mouthwash.

Eye: During radiation therapy, the eye and conjunctiva (pink tissue around the eye) will become reddened. It is possible for the surface of the eye (cornea) to be injured. This is painful and you might notice squinting. Please notify us if you notice any changes in the eye or squinting. We will use eye medications as needed to keep your pet comfortable and help the eye to heal. It is imperative that your pet wears an E-collar to prevent serious damage to the eye. Radiation therapy injures the tear glands and can result in decreased tear production. A radiated eye may require life-long medication.

Weight loss: Food must be withheld after midnight the night before radiation therapy because of anesthesia. This is not a problem for most dogs, but for cats that tend to eat their food slowly through the day or at night, this may result in weight loss. We will monitor your pet’s weight during treatment and discuss methods of maintaining body weight as needed. This may include feeding more often, feeding more palatable foods, hand feeding, and the use of appetite stimulants.

Late side effects generally do not occur until at least 6 months to one year after radiation therapy. These effects are more serious because they do not heal. With the exception of palliative radiation therapy (where we do not expect a patient to live long enough to experience these effects), our protocols are designed to reduce the risk of serious late side effects to less than 5%.

Skin: Late side effects involving the skin are common. These are changes in the skin that will not affect your pet’s quality of life. The skin in the radiation field will change in texture (feel more like scar tissue) and darken (hyperpigmentation). The amount of hair regrowth varies from patient to patient. Some patients do not grow hair in the radiation field, some grow patches of hair, and some grow all of the hair back. What hair grows in the treatment field will be white. The radiation field can develop sunburn if not protected from sunlight. The field should be kept out of the sun, or blocked using sunblock for babies or protective clothing. If you should notice any changes in your pet’s radiation field (a lump, swelling, or redness), please call us.

Eye: A radiated eye will commonly be left with decreased tear production requiring life-long medication. Over time a cataract will develop. Very rarely, blindness due to retinal damage or severe injury necessitating removal of an eye can occur. All radiated eyes are monitored closely during and after radiation therapy. Should you ever notice that your pet’s eye is red or squinty, please call us.

Mouth: The mouth will generally heal and return to normal. Rarely a patient may develop necrosis (death) or infection of bone in the jaw.

Bone: Rarely, bone underlying a radiation site may develop necrosis.

Second Tumors: It is uncommon, but possible, for patients to develop second tumors in the radiation field. This happens in less than 5% of radiation patients and usually occurs at 5 or more years after radiation therapy.

Follow-up Visits for Radiation Patients

Radiation patients are rechecked at about 2–4 weeks after radiation therapy to evaluate and treat acute side effects. After that visit, radiation patients are rechecked at 2-3 months after radiation therapy and then every 3 months. These visits allow the oncologists to evaluate your pet for recurrence of tumor and for radiation side effects. This schedule may be altered based on tumor type or if any concerns should arise.

Download the Radiation Therapy Client/Patient Handout [PDF]

Information for Referring Veterinarians

Go to the hospital referral page for general instructions about how to make a referral, and to download the general referral form.

The Oncology consultation form [PDF] may be downloaded here.

Funds for Cancer Research and Treatment

Trot for the Cure

Join us each year as we - along with a couple hundred of our closest two- and four-legged friends - walk and trot toward a cure with this fundraiser for cancer research in Charleston, S.C.

UGA CaRES for Pets Fund (Cancer Research, Education and Service) / Nicky Fund for cancer research and treatment brochure [PDF]

Doggie Dash: The College of Veterinary Medicine Canine Club holds an annual fundraiser to support research on cancer in companion animals.

This page was last updated January 13, 2009.