Radiation Therapy

How Radiation Therapy Works

Radiation therapy uses ionizing radiation to damage the DNA in tumor cells, resulting in tumor cell death.

The most common type of radiation therapy is external beam radiation therapy, also known as teletherapy. Teletherapy is delivered by a radiation-producing machine like a linear accelerator, or from a machine housing a radioactive source, such as a cobalt machine. The patient is precisely positioned on a table, also called a couch, near the machine. Radiation travels from the machine to the patient, where the radiation dose is delivered to the tumor, impacting normal tissues as little as possible. While the patient remains in the exact same position, the machine revolves around the patient so that radiation is delivered from many different angles.

Each treatment takes just a few minutes and does not cause any discomfort.

Radiation usually is administered with the goal of achieving long-term tumor control. This is referred to as radiation therapy with curative intent. Depending on the part of the body bearing the tumor, most veterinary patients treated with curative intent protocols are treated over a three to four week period. A small "fraction" of radiation is delivered each day. Sometimes there can be side effects, known as acute effects, from this type of treatment, depending on the location. New technology is helping minimize acute effects.

Palliative Radiation Therapy

Sometimes radiation is administered to relieve the patient of pain and/or improve regional function and hygiene. This is referred to as palliative radiation therapy. Palliative protocols are commonly used when the patient has advanced cancer with tumor spread to other locations, or some other critical condition that would limit life expectancy. These protocols vary and may involve weekly treatments or treatments given over the course of a few days.

Palliative radiation therapy usually relieves pain and may even cause tumors to shrink a bit. Palliative therapy rarely causes acute effects. Unfortunately, the duration of patient response is far shorter than patients treated with more aggressive (curative) protocols.