In the past several decades, radiation therapy in veterinary medicine has become a routine part of the management of companion animals with cancer.

Radiation therapy is a local treatment and is indicated in two main settings, definitive for long term control, or palliative for pain relief and improved quality of life.

6 Mv Linear AcceleratorThe goal of definitive radiation therapy is eradication of all viable tumour cells within the patient. Its intent is to cure the patient of the tumour whenever possible and even if not possible to prolong survival as long as possible. It often involves the combination of oncologic surgery, radiation therapy and chemotherapy. Patients with unresectable tumours, metastatic disease or significant underlying problems may not be candidates for definitive radiation therapy and would be better managed with a palliative course of therapy.

Palliative radiation is playing a larger role in veterinary oncology as owners are seeking to improve quality of life, decrease pain and minimize hospitalisation rather than achieving a cure and prolonging survival. Most palliative protocols use lower total doses and a higher dose per fraction to accomplish the goals listed above. Owners must understand that this approach means not only that tumour control may be short term compared to definitive therapy, but also the risk for late effects are increased in the event the patient lives longer than expected.

Because each cancer is different and each case particular, we offer our patients a range of treatment protocols adapted to their specific situation. Quality assurance is critical in radiation oncology and VRCC radiotherapy service has followed the most recent advances in term of treatment scheme, treatment planning, dose calculation and patient positioning. For head and neck, spinal, thoracic and pelvic tumours, computer assisted planning allows three-dimensional visualization of the dose within the entire patient and give our radiation oncologists the opportunity to treat most cases with an increased accuracy and safety for our patients.

Historically, radiation therapy has been delivered to patients when complete excision is not possible or if surgery would result in functional or cosmetic compromise. It is becoming clear however, that there are situations where radiation therapy can be given before or during surgery. Therefore, consultation with a radiation oncology is indicated at the time of diagnosis prior to definitive therapy, especially in situations where a complete excision is unlikely.

Evaluation of patients after radiation may be as important as the treatment itself to identify and manage local recurrences and treatment related sequela. It is imperative to document the response to therapy over time and note the maximal response. Not all tumours will completely regress but failure to shrink is not indicative of treatment failure.

Rechecks are also extremely important to identify radiation-induced late effects so intervention can be implemented if possible. Although many late effects can only be managed with surgical excision, it is always best to deal with these early in their development before surgical excision is not possible.