Radiotherapy in Cats

Radiotherapy is a means of treating certain cancers in the cat. The aim is to damage and kill the cancer cells that make up a tumor, while preserving healthy tissue. Not all cancers are amenable to radiotherapy because of their type or location. Indeed, not all patients are candidates for radiotherapy since each treatment requires a full general anesthetic. 

In addition, there are relatively few specialist centers with the necessary equipment and expertise to offer radiotherapy, which can mean a considerable journey in order to reach an appropriate specialist. This may mean it's not practical to undertake a course of radiotherapy since regular weekly visits are usually required. 

The patient is carefully screened for suitability to undergo the repeated anesthetics necessary for radiation treatment. Protocols differ but the cat may need repeat sessions on a weekly basis for several weeks, or therapy on alternate days. For the latter it may be best for the cat to be hospitalized for the duration of treatment in order to avoid the rigors of travel. 

It is crucial the cat stays absolutely still during treatment, as movement could lead to irradiation and damage to healthy tissue. The cat will be anesthetized and monitored remotely using equipment that reads out in the adjacent viewing room. 

The first session likely involves a fresh CT scan (even if the cat has had a previous scan as part of the diagnostic work up) so that the exact tumor margins can be assessed and the radiotherapy beam focussed in exactly the correct place. 

Fur will the shaved and the skin marked up with a permanent marker to facilitate positioning of the radiation beam. The duration of each exposure will depend on the type, size, and location of the tumor. 

After each irradiation, the patient wakes up and is allowed home, usually the same day (for those not boarding at the hospital).

Radiotherapy is rarely the first option for treating a tumor. Where, possible complete surgical removal  or chemotherapy is prefered. However, for tumors that are not suitable for surgery, radiotherapy offers a highly effective, and life-extending treatment. 

Radiotherapy is not used in the same way in cats as in people. In the latter, much higher doses of radiation are used with the aim of curing in the patient. However, much lower doses are used in cats, with the aim of extending good quality life (rather than a cure) with a minimal amount of distress to the patient.

Radiotherapy is very good at what it does, which is: 

• Destroying tumors at inaccessible sites
• Shrinking down tumor size
• Pain relief
• Part of a wider spectrum of treatments which may include chemotherapy or surgery

Lower doses of radiation are used in cats, which means less discomfort post-treatment. Once awake from the anesthetic the cat may experience a short period of discomfort but this soon passes. Indeed, radiation is sometimes used for pain relief as it also damages the nerve supply to the tumor. 

In the longer term, the fur in the irradiated area may grow back white. Also, the irradiated skin may be lesion resilient in the future and more prone to infection or damage, but this is easily managed with appropriate antibiotic cover. 

Not only is the actual procedure expensive but there will be associated costs such as for travel and accommodation for those who live some distance from the referral center. 

A consultation with a veterinary oncologist can be around $250 - $300. A repeat CT scan is needed, at around $630 - $2,000. The cost of a remotely monitored anesthetic will vary according to the length of each treatment. The most sophisticated anesthetic agents are used, and typically anesthesia comes in at $140 or more. Finally, comes the cost of the actual radiation treatment itself. The cost will vary widely depending on whether the aim is to kill the cancer or provide palliative care, but is likely to be thousands of dollars. 

Radiotherapy is a relatively new science for the treatment of cats. It offers the potential to extend life in what might otherwise be hopeless cases, but unfortunately the therapy is costly and not widely available. 

Before you commit to a course of radiotherapy it is important to weigh up the character of your cat and how they will cope with travel and repeated anesthetics. For example, if they hate travelling and spend the next two months making long journeys on a weekly basis, and radiotherapy only extends life by four months, then you have to weigh up if this is truly beneficial to the cat or not. 

Radiotherapy is often used when surgery is not an option. By being vigilant and checking your cat weekly for lumps, you are more likely to detect tumors at a stage when they are still amenable to surgical removal. 

Most cancers in cats occur spontaneously, and so prevention of cancer is a goal yet to be achieved.