Radiotherapy

Pets today are healthier and, in general, living longer than ever before. However the increasing numbers of aging pets mean that they are at increasing risk of developing cancer later in life. It can be very frightening when you hear that your pet has cancer but veterinary care has advanced rapidly over recent years and there may well be an effective treatment for your pet.

Radiotherapy uses radiation (like a powerful type of X-rays) to damage and destroy cancer cells. The radiation can be administered in a number of ways but when it contacts cells it causes permanent damage. Most commonly radiation is delivered from an external source for a short period of time on a regular basis (external beam therapy). Radiation delivered in high doses can do damage very rapidly so a short exposure to the radiation beam will damage the cells which die off over the next few days.

The aim with radiotherapy is to give a high dose of radiation to the cancer cells (doing maximum damage) whilst minimizing the dose to the rest of the body.

It is quite expensive to have radiotherapy and you will probably have to travel to a specialist center to get treatment so your veterinarian will not recommend the procedure unless they think it is likely to help in the treatment of your pet. Cancers can be treated using surgery, drugs (chemotherapy), radiotherapy or often a combination of these. Each type of cancer is best treated in a particular way and if your veterinarian has recommended one form of treatment it is likely that this is the best option for your pet. However, if you are concerned about the treatment then discuss your worries with your veterinarian.

Radiotherapy is usually given as a course of treatments. It is very important that all treatments in the course are given at the right time so make sure before agreeing to treatment that you can take your pet for every session. The damage to cancer cells caused by radiotherapy builds up over time so each treatment kills off cells missed by the previous one. The time between each treatment in the course allows the normal healthy tissues to recover and grow. So the course maximizes the damage to cancer cells whilst reducing the risk of side effects.

Many owners are worried by the idea of radiotherapy for their pet because they have heard of the side-effects suffered by human cancer patients. In people the aim of cancer treatment is to kill all cancer cells and cure disease doses of radiotherapy are therefore high and side-effects such as vomiting and hairloss are relatively common. Although it does sometimes cure cancer, the aim of cancer treatment in pets is to prolong a good quality of life (rather than necessarily trying to cure the cancer). This means that treatment sessions are designed to have the maximum beneficial effect without causing severe side effects. Your pet should remain well throughout the course of treatment.

If your pet is having external beam radiotherapy the radiation does not stay in their body so they are able to come home between treatments. However, it is very important that the treatment is delivered at regular intervals and so if the treatment interval is short (eg alternate days) your veterinarian may recommend that they stay in hospital so that you do not have to keep travelling back and forward.

It is essential that your pet remains still throughout the whole treatment as this must be directed at a very specific area of the body. Severe damage can be caused if the radiation beam strikes the wrong tissue during the procedure.

Modern anesthetics are very safe and your pet will probably recover more rapidly from an anesthetic than any form of sedation. As radiotherapy is usually performed at specialist centers it is likely that your pet’s anesthetic will be monitored by a veterinarian with a special interest in anesthesia and the anesthetic will be very safe. You will usually be able to take your pet home as soon as they have recovered from the anesthetic unless they are receiving further treatment.

As your pet will be having an anesthetic your veterinarian will ask you not to feed your pet the evening before the day of the treatment. Occasionally drugs are given before treatment to increase the effect of the radiation on cancer cells if your veterinarian gives you specific instructions make sure you follow them carefully.

There is a small risk associated with repeated anesthetics, but your pet’s health will be closely monitored and modern anesthetics are very safe.

Radiotherapy is a very powerful treatment and the aim is to give a dose that will destroy most of the cancer cells whilst allowing the normal tissue to recover between treatments. Some cells are very sensitive to the effects of radiation so when treatment is planned your veterinarian will try to avoid particularly sensitive areas (such as the eye). After treatment the area of skin around the tumor may become red or sore looking. Your veterinarian will prescribe tablets if they are concerned about your pet, but if you are worried make sure you voice your concerns at your next visit. Long term problems are usually changes at the site of the treatment such as bald patches or white hair regrowing (where it should be colored).

If your pet has had an anesthetic they should be fully recovered by the time you get home. Offer a light meal at tea time but do not be alarmed if your pet does not want to eat until the following day. Often a course of radiotherapy is given after a cancer has been removed if your pet has stitches keep a close eye on these as the radiation treatment may delay healing and the wound could open up.

If your pet is receiving medication for other conditions check with your veterinarian that you should continue these throughout the radiotherapy course.