The radiation oncologist determines the number of treatments after considering the tumor type and location. Each treatment requires that your pet stay completely still for 10-20 minutes, so a short-acting general anesthetic is given each time. Blood tests, x-rays (radiographs) and careful monitoring minimizes the risk associated with anesthesia.
Stereotactic radiation therapy offers the shortest treatment schedule. The entire radiation dose can be delivered in 2 or 3 sessions lasting less than 15 minutes each, greatly reducing the number of times a patient must undergo anesthesia and treatment is usually completed within one week. Definitive radiation treatments are given over 5 consecutive days or twice a week over 3-4 weeks. When radiation is given palliatively to control pain, treatments are given once every 3-4 weeks, or over five consecutive days.
What to expect following radiation treatment
After every treatment, patients return home with their families and can experience their normal routines. Once all treatments are finished, follow up visits with the oncologist will be scheduled for one week post-treatment and then three months post-treatment. This is recommended because the effects of radiation can occur over the following days, weeks, or even months, and it’s important for the oncologist to monitor the recovery process. Some tumors will just stop growing, while others will eventually disappear.
As with any type of cancer therapy, certain side effects can occur with radiation therapy. Since radiation therapy is limited to one region of the body, side effects are also restricted to that area. With stereotactic radiation therapy or palliative radiation therapy, side effects rarely occur, but are more common with conventional radiation and IMRT. If side effects occur, most begin after 10 to 12 treatments and heal approximately 2 to 5 weeks after therapy ends. If acute side effects occur, we keep our patients as comfortable as possible with pain medications and anti-inflammatories. If radiation includes the mouth or nose, ulceration of the moist tissue of the mouth can occur (called mucositis). Oral rinses, soft foods, and topical numbing agents can reduce discomfort. Since radiation can temporarily decrease taste and smell, warmed “smelly” foods such as pureed meat baby foods and fishy cat foods can increase appetite. The skin covering a tumor treated with radiation therapy may become dry and flaky or moist and red, somewhat like severe sunburn. The radiation oncologist can recommend safe ointments and gels to prevent irritation. If one or both eyes are near the radiation field (common for nasal and brain tumors), tear production may decrease, and your pet may require eye drops during and after therapy. Radiation therapy can also cause long-term side effects. Hair loss, which is limited to the treatment area, may be permanent. Any hair that returns will typically be a different color. Other delayed effects from radiation can occur in bone, spinal cord, and brain tissue, as well as the lens and retina of the eye. These changes may not occur for months or even years following the radiation treatments. Because these effects can be permanent, a radiation oncologist must carefully supervise the dose and method of radiation for your pet.
Radiation therapy can slow or prevent local recurrence of many types of cancer.