Radiation Therapy

Point of Excellence: State-of-the-art radiation therapy.

Our treatment goal is to deliver the optimal doses of radiation necessary to kill cancer cells without damaging healthy tissue. The key to doing this is our new Linear Accelerator, the first veterinary unit in Canada with Intensity-Modulated Radiation Therapy capabilities. This technology allows us to create highly complex, 3 dimensional shapes that conform to the tumour outline and to finely control and modulate the intensity of the radiation beam and deliver different doses of radiation to different areas within the treatment field. Click for more information about IMRT (PDF)

Radiation therapy is primarily designed to achieve control in localized area. It is often used in conjunction with surgery to try to cure cases where surgery alone is either not possible or where it would result in significant disfigurement or loss of function. Many tumours with locally aggressive behavior can be controlled or even cured with surgery and radiation therapy.

Radiation therapy may often be used as an adjunct to treating cancers with a systemic behavior as well. For some tumours, using radiation to achieve local control with adjuvant chemotherapy to prevent or delay systemic metastasis can be a very successful strategy.

Point of Excellence: Precision Targeting

The linear accelerator at WVCC will be the only veterinary unit in Canada, and one of only a very few units in all of North Amercia to have IMRT capabilities. This means we have the ability to create highly complex shapes that conform to the tumour outline, to more precisely target treatment while sparing normal tissue. The IMRT collimator, also known as a dynamic multi-leaf collimator (dMLC) works by linking a 3-dimensional radiation planning workstation to a collimator that is computer controlled. Rather than just moving in an x-y direction, its multiple leaves can move independently of each other allowing the computer and linear accelerator to create highly complex shapes that conform to the tumour outline, while sparing normal tissue.

Additionally, the dMLC constantly moves during dose delivery, allowing small segments of a field to receive relatively more (or less) radiation. This allows very fine control of the dose delivered to normal tissue, while maximizing the dose delivered to tumour. These small changes in field shape decrease the intensity of the radiation beam (hence the term intensity modulate) ? allowing different areas within the treatment field to receive different doses of radiation.

Finally, radiation therapy may be used in a palliative setting. For some cancers, significant pain relief and return to function can be achieved with just one or 2 doses of radiation. For patients with bone lesions, radiation therapy may be the most effective method of pain relief available. Most radiation therapy protocols are 18-21 fractions given over 4-7 weeks. Veterinary patients must be anesthetized for each treatment.

Most of the side effects of radiation therapy are mild and self limiting. Severe radiation toxicity is an uncommon thing in veterinary medicine, especially in patients treated with advanced field shaping techniques. The normal tissue in the field is always dose limiting - you must consider the normal tissue within a radiation field when setting up the treatment fields. The ability to spare normal tissues while targeting the tumour is the most important aspect of current radiation therapy practice and research. Sometimes, cancers must be treated to sub-optimal doses because of the normal tissue within the treatment field. Newer dose delivery techniques, such as Intensity Modulated Radiation Therapy (IMRT) allow more aggressive treatment of tumours while substantially sparing normal tissues.