Radiation therapy (sometimes called radiotherapy, x-ray therapy, or irradiation) is the treatment of disease using penetrating beams of high energy waves or streams of particles called radiation. It is similar to x-rays, but is delivered in doses many times higher than those of x-rays.
The radiation used for cancer treatment in dogs comes from special machines that your local veterinarian may not have. You may need to be referred to a specialized oncology practice for this type of treatment. Radiation therapy equipment aims specific amounts of the radiation at tumors
or areas of the body where there is cancer. Many tumors thought untreatable in the past are responsive to radiation therapy.
Radiation in high doses kills cells or keeps them from growing and dividing. Because cancer cells grow and divide more rapidly than most of the
normal cells around them, radiation therapy can successfully treat many kinds of cancer. The more cells multiply, the more sensitive they are to
radiation. Normal cells are also affected by radiation but, unlike cancer cells, most of them recover from the effects of radiation.
To protect normal cells, veterinarians carefully limit the doses of radiation and spread the treatment out over time. They also shield as much normal
tissue as possible while they aim the radiation at the site of the cancer.
There are two approaches for using radiation therapy in dogs; curative and palliative. In order to attempt to cure certain cancers, an intensive
protocol will be ordered which usually requires outpatient radiation treatments for 16 to 20 days Palliative radiation therapy is a less intense
protocol, and can be described as comfort care. The intent of palliative therapy is to provide relief from cancer symptoms and maintain a good
quality of life in dogs whose long-term cancer control is not possible. Palliative radiation therapy can be used to control pain, bleeding, and loss of
Radiation therapy is an effective treatment for many types of cancers in almost any part of the body and can be utilized alone or in combination with
chemotherapy and surgery. Radiation treatment, like surgery, is a local treatment in that it affects the cancer cells only in a specific area of the
body. Some of these cancers will respond to radiation therapy and provide the animal a good quality of life. Radiation therapy is commonly used as an adjunct to treating
many types of inoperable cancers, such as lymphosarcoma, mast cell tumors, carcinomas (skin cancer), and sarcomas (cancer of bone, muscle, or connective tissue).
Radiation therapy is often used with surgery to treat cancer. Veterinarians may use radiation before surgery to shrink a tumor. This makes it easier to remove the cancerous
tissue and may allow the surgeon to perform less radical surgery.
Radiation therapy may be used after surgery to stop the growth of cancer cells that may remain. Your veterinarian may choose to use radiation therapy and surgery at the
same time. This procedure, known as intraoperative radiation.
Radiation therapy treatments are performed while the dog is under general anesthesia, using a machine that directs a beam of high-energy rays at the tumor. The treatments
take only a few minutes and are normally done on an outpatient basis. Radiation therapy is not painful. Most dogs do quite well with this type of treatment.
The brief high doses of radiation that damage or destroy cancer cells can also injure or kill normal cells. These effects of radiation on normal cells cause treatment side
effects. These side effects may include a sunburn-type skin reaction, hair loss, inflamed mucus membranes, and diarrhea. Not all dogs develop side effects, but if they do,
they generally subside within 2-3 weeks.