Radiotherapy in Veterinary Medicine

There are three different kinds of radiation : alpha-radiation, electron radiation (beta) and gamma emissions. Which kind of radiation is used depends on the disease being treated.

Radiotherapy treatments in veterinary medicine are used only in combination with surgery or chemotherapy. Radiotherapy is useful when the tumour cannot be totally destroyed and the prognosis of chemotherapy is poor. Radiotherapy can take place before surgery to minimize the tumour, thus making it easier to remove; or after surgery to destroy those parts of the tumour that could not be removed during surgery. In combination with chemotherapy, radiotherapy can increase the animal`s chance of survival.

The most frequently conducted form of radiotherapy is local radiation, however, there is also the possibility of systemic radiation (radiation of the entire body). An example here is the treatment of thyroid cancer. Cats are given the iodine 131 isotope (radiated iodine), then the injected iodine accumulates in the thyroid and there radiates the thyroid tumour. The treatment is either curative , meaning it heals the animal, or is palliative, in which case the tumour is reduced and the quality of live is improved.

Which diseases are treated with radiotherapy? Radiotherapy is used to cure tumour diseases and chronic joint diseases. During cancer treatments, radiotherapy is most often used for large neoplasms , or those in critical areas such as the brain, and which can not be removed by surgery. It is the therapy of choice for most brain tumours, nasal tumours, and other neoplasms of the head, neck, the thyroid, the nasal cavity and the skin. It is also the only option for cancer of the vertebral column and pelvic canal. Radiotherapy is also used to treat tumours in the mediastinum and soft tissues of the skin and subcutis either before or after surgery. The tumours that are most sensitive to radiation are specific forms of lymph node cancer and the Sticker-sarcoma (type of cancer occurring on the external genitals of dogs).

Gonarthrosis and arthrosis of the cubital joint can be treated with radiotherapy as well.

What treatments are used? The most frequently used radiation therapy is external beam radiotherapy (or percutaneous radiation therapy). For this, a strong radiation source produces a beam of high-energy radiation that is directed onto the cancerous tissue. Another radiation method is „ brachytherapy “ die Brachytherapie (also called internal radiation), which uses much smaller radiation sources applied onto or close to the tumour, or that implants radiocative material within. Thus, the radiation source is within the body of the animal.

The third method is „biologically targeted radiotherapy“ (or nuclear oncology), where radiopharmaceuticals are very precisely directed to the tumour cells via specific cellular mechanisms. Today, its application is limited to only a few cancer types.

How do the animals tolerate radiotherapy? The most successful and least harmful types of radiotherapy are those directed towards the body surface and oral cavity.

However, acute risks include:

Fur loss (in the area that receives treatment) Dermatitis (resembling sunburn) Development of non-healing wounds Pathological fracture (in rare cases) New tumours at the irradiated site (in very rare cases). Where is veterinary radiotherapy conducted ? In Germany, only four facilities conduct radiotherapy for animals and very few radiologists now actively practice in both the fields of imaging and therapy of animal diseases.

Depending on the disease, three to ten appointments may be necessary. Animals cannot receive daily irradiations since anaesthesia is necessary to keep the animals immobile. The radiation itself only takes a couple of minutes. Therefore, patients are treated about three times a week for a couple of weeks. About 50 % of animals are successfully treated after three to four weeks. The treatment stays successful for up to one year; of course, depending on the cancer type and stage, and the age of the animals.

EXERCISE: 1. What are the acute risks for animals after radiotherapy?

a) Dermatitis b) Headache c) Pathological fracture d) Conjunctivitis

2. Radiotherapy in veterinary medicine is used for

a) Thyroid cancer b) Brain tumour c) Cancer of the pelvic canal d) Neoplasms e) Skin cancer

3. Which of these methods uses an external radiation source?

a) Percutaneous radiation therapy b) Brachytherapy c) Biologically targeted radiotherapy

You’ll find the answer on the next page.

BIBLIOGRAPHY 1. http://dict.leo.org 2. Santoro A.: Handbook of Veterinary Medicine, Callisto Reference, 2016. 3. www.dict.cc 4. www.webster-dictionary.org

Carmen Lobitz ist freie Trainerin, Lehrerin und MTA. Sie gründete 1998 in Berlin lobitz seminare, die unter anderem Englischseminare für Health Professionals anbieten. Kontakt: mail@lobitz-seminare.de www.lobitz-seminare.de

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Lösung für Exercise: 1. A + C 2. A–E 3. A

Radiotherapy in Veterinary Medicine

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