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Types of Cancer > OncoLink Vet > Veterinary Oncology > Treatment Options

Radiation Therapy Information

Clinical Oncology Service
Affiliation: Veterinary Hospital of the University of Pennsylvania (VHUP)
Last Modified: November 17, 2008

How does radiation therapy work?

Radiation, when used at energies that are a thousand times the energies used to produce a chest X-ray, can kill cells. Both normal and cancer cells are affected, but radiation treatment is intended and designed to maximize tumor effect and minimize normal tissue effect. Maximizing tumor effect is one reason that radiation treatments are given as a series of many small doses, rather than a few large doses.

What are the benefits of radiation therapy and when is it used?

Radiation therapy is used to treat localized disease. It can be used in the management of cancers that cannot be treated successfully by surgery or chemotherapy alone. Typically, it is employed following surgery when there are tumor cells remaining after excision, either because of the biology of that cancer and the nature of its growth, or because complete surgical removal would involve a very extensive procedure involving vital structures. In some instances, radiation therapy may be employed before surgery or chemotherapy in an attempt to shrink a tumor down to a more manageable size. Radiation therapy can offer, in some instances, permanent control of a tumor.

Even when a cure is not possible, radiation therapy can still bring some relief. Shrinking a large tumor with radiation therapy may improve a pet's quality of life by reducing pressure, bleeding, or pain. This is called palliative treatment.

Are there risks involved?

There are some risks involved with any type of cancer treatment. In addition to cancer cells, some normal cells will also be killed by the radiation. Some side effects may be apparent because of normal cells being killed (e.g. "radiation dermatitis"). Usually these side effects are outweighed by the benefits of killing cancer cells.

In addition, radiation therapy requires the animal to be perfectly still during treatment. Thus, anesthesia is necessary for each treatment. There is always a very slight risk associated with anesthesia.