Radio-iodine treatment for thyroid cancer

Thyroid cancer (hyperthyroidism or over-active thyroid gland) is quite common in middle-aged cats. If your cat has been diagnosed with cancer of the thyroid gland there may well be an effective treatment for your pet. The disease can often be successfully treated by surgery but a form of radiotherapy (radio-iodine treatment) is another option and this has fewer complications and a higher success rate than surgery or other forms of treatment.

Radiotherapy uses radiation to damage and destroy cancer cells. The radiation can be administered in a number of ways. However the radiation is given, when it contacts cells it causes permanent damage. In some types of cancer radioactive implants can also be placed in the cancer itself, for treatment of others a beam of radiation is delivered from outside of the body. Cats with cancer of the thyroid gland can be treated with radioactive injections (radio-iodine therapy).

In the treatment of thyroid cancer a radioactive injection is given under the skin. The radioactive material enters the blood and is transported around the body – radiation is concentrated in the cancer cells of the thyroid glands whilst the rest of the body receives a lower dose. The aim with radiotherapy is to give a high dose of radiation to the cancer cells (doing maximum damage) whilst minimising 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 centre to get treatment so your vet will not recommend the procedure unless they think it is likely to help in the treatment of your cat. There are many ways of tackling cancer – surgery, drugs (chemotherapy), radiotherapy or often a combination of these. Each type of cancer is best treated in a particular way and if your vet 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 vet.

Thyroid cancer is quite common in middle-aged cats. It can often be successfully treated by surgery but this requires a general anaesthetic. Radio-iodine treatment has fewer complications and a higher success rate than surgery or other forms of treatment.

In people the aim of cancer treatment is to kill all cancer cells and cure disease – doses of chemotherapy 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 side effects. Your pet should remain well throughout the course of treatment.

Radio-iodine treatment is generally the safest method of treating thyroid tumours in cats. However, it is not suitable for cats with other diseases that require regular monitoring and therapy as cats have to remain in isolation during the treatment. People looking after cats receiving radio-iodine therapy cannot handle them while they are radioactive.

In most cats the treatment destroys all the cancer and the disease does not come back. However in a few cats the disease might come back months or years after treatment.

If your pet is having a radioactive injection or implant they will be giving off radiation for the time the radiation is active. Although the dose of radiation is unlikely to be harmful to a healthy person there are long term risks associated with radiation exposure so pets are kept in special areas of the hospital for the duration of treatment. Cats will usually be kept in isolation for 4 weeks, and may have to stay in hospital for longer than this. They will only be released from hospital when it is safe to do so – so you do not need to adopt any special precautions once they come home.

There should be no particular problems once your pet comes home – if you are concerned about any aspect of their health contact your vet for advice. If your pet is receiving medication for other conditions check with your vet that you should continue these throughout the radiotherapy course.

Signs should start to resolve within 2 weeks of injection but a full response may take up to 3 months. Most cats only need one course of treatment but sometimes a second injection is needed.

Cancer of the thyroid gland is relatively common in cats but can usually be easily controlled. It is important that treatment starts early before other damage has occurred in the body.