Whenever radiation therapy is planned for a pet with cancer, quality of life and freedom from any discomfort is a priority. Like surgery, radiation is a regional treatment. It is usually given to the tumor site and one to six centimeters of 'normal' surrounding tissue, depending on the extent of microscopic disease. In order to minimize the adverse effects of radiation therapy and to enhance the control of the cancer, small dosages of radiation are administered over several weeks. During each treatment, your pet will be placed under a light level of anesthesia and a machine will be used to precisely direct the radiation therapy beams over several minutes. The radiation oncologist will determine the appropriate dosage and number of treatments to ensure the best outcome possible. When radiation is used with the intent of eliminating or controlling the cancer for a long period of time, 9 to 30 treatments are administered over 3 to 6 weeks. Each treatment takes only a few minutes to administer and the actual radiation is not painful.
In the course of radiation treatment of your pets cancer, some surrounding normal tissue will be affected. The radiation-induced effects to normal tissues usually do not begin until the end of the therapy period and they continue for several weeks after the treatments have ended. These are called the acute side effects. They usually resolve within a few weeks to a month after radiation has been completed. Other adverse effects associated with radiation therapy may occur many months or years after radiation is complete. These are called late radiation effects. We will work with you to ensure that your pet is as comfortable as possible during this two to four-week period when adverse effects are noted. While the adverse effects of radiation therapy are difficult to predict, a few of the most common possible effects are listed below. Our new equipment will dramatically decrease the acute effects for some types of cancers.
Potential Side Effects:
Radiation reactions that may appear toward the end of radiation therapy include loss of hair and a sunburn-like effect to the skin that may become itchy, dry or moist. Oral or injectable medication to reduce itching or discomfort may be helpful, whereas applying oily ointments usually reduces the rate of healing. Most pets develop a change in the color of the skin and hair in the area being treated and, occasionally, hair will fall out and not re-grow in that area. Other changes to the skin that are much less common include formation of a non-healing wound and the formation of thickened scar tissue in the area being treated.
If your pet is being treated for a tumor in or around the mouth, injury to this area can result in a sunburn-like effect to the tongue and the tissues lining the mouth. This can result in loss of appetite, altered tongue function and tenderness to the lining of the mouth. Fortunately, our new equipment should be particularly useful in decreasing acute efects for tumors in the nasal and oral cavities. If your pet has lost a significant amount of weight before or during treatment, you may be asked to consider assisted tube feeding. Assisted tube feeding is the placement of a small tube into the esophagus (esophagostomy tube), stomach (gastrostomy tube) or intestine (jejunostomy tube) to allow the non-painful administration of food, water and medicine which will bypass the mouth when it is hurting. The key is to begin this assisted tube feeding before significant weight loss is observed. During radiation therapy, you may want to gently rinse your pets mouth out with a cool green tea solution. Some recommend mixing Maalox with water to coat the mouth. Your veterinarian may recommend some additional therapies if your pet stops producing enough saliva.
Large Intestine and Rectum
Occasionally, the large intestine (colon) and rectum (area just inside the anal opening underneath the tail) are affected when tumors in that area of the body are being treated. Most pets have only mild, transient side effects that can include loose stool (bowel movement) that may contain blood, and perhaps some discomfort passing stool. A special diet, stool softeners and, in some cases, medicated enemas may be beneficial. Whenever the anus and the area around it are injured by radiation therapy, the area should be gently cleansed using soap and water, and dried thoroughly.
The eye is often unavoidably in the treatment field when tumors of the facial skin, sinuses or nasal cavity are treated. While most pets do not show any adverse effects associated with damage to the eye itself, side effects can include cataract formation months to years after therapy is finished, damage to the retina (which is in the back of the eye), decreased tear production, and irritation to the tissues around the eye. Occasionally, an ulcer of the cornea (the outer layer of the eye) may be noted. In some cases, medicines may be needed to treat these conditions.