Radiotherapy Radiotherapy

Although originally employed as a method of treatment in veterinary patients as early as 1906 by Dr R. Eberlein in the Berlin veterinary school, radiotherapy is still only available at some of the veterinary schools, and a few other institutions in the UK. For this reason no details about recommended radiation dose rates will be given as it is still a specialist field and should only be performed in experienced referral centres.

Whatever the method of delivery of the radiation (by irradiation from a beam of orthovoltage X-ray or cobalt-60 gamma rays; by the surgical implantation of radioactive implants (cobalt or caesium needles); by the use of strontium probes; or by the parenteral administration of a radioactive substance such as radioiodine) the clinical challenge of using radiotherapy is to deliver a therapeutic dose of radiation to the target site while minimising its delivery to normal tissues in order to avoid excessive damage to normal tissues.

Radiotherapy is indicated for tumours which are not amenable to surand it is most successful when applied to certain tissue types - notably rapidly dividing cells. Table 6.9 gives an outline of the sensitivity of different cell types to radiotherapy.

Side-effects of radiotherapy are listed in Table 6.10 and these should be minimised by restricting the area of exposure of normal tissue as much as possible.

During therapy these changes can lead to serious gastrointestinal disorders but fortunately the most radiation-sensitive tissues (e.g. epithelial surfaces) are also the most rapid to heal.

Neoplasms that can be successfully treated using radiotherapy include:
  • cutaneous squamous cell carcinoma
  • oral squamous cell carcinoma
  • localised lymphoma, e.g. mediastinal lymphoma
  • fibrosarcoma
  • solitary mast cell tumours (dogs - but not in cats in which mastocytoma is usually multifocal/systemic
  • thyroid adenoma (cats)