Veterinary Cancer Group has been a leader in radiation therapy since 2007. Both Dr. Jarred Lyons, located in our Culver City and Woodland Hills offices, and Dr. David Bommarito, located in Tustin, are board-certified practitioners of this form of cancer treatment in pets. Radiation therapy uses a beam of energy focused at the tumor region to gradually eliminate cancer cells, and is often used in conjunction with surgery and/or chemotherapy.
Veterinary Cancer Group utilizes state-of-the-art, on-site Varian Trilogy Linear Accelerators to provide a variety of options for radiation treatment, including Definitive Radiation Therapy, Palliative Radiation Therapy, Image-Guided Radiation Therapy (IGRT), Stereotactic Radiotherapy (SRT), Intensity-Modulated Radiation Therapy (IMRT), and Strontium-90 Plesiotherapy. Veterinary Cancer Group’s linear accelerators feature cone beam CT scanners and other on-board imaging, allowing clinicians to rapidly and confidently visualize the tumors they are treating. The Varian Trilogy shortens patient treatment times, minimizes damage to healthy tissues, and provides a more comfortable, less stressful experience for the patient.
Stereotactic Radiation Therapy
Dr. Lyons and Dr. Bommarito were among the first veterinary radiation oncologists to treat animals with stereotactic radiation therapy. Stereotactic radiation therapy, also known as SRT, uses focused radiation beams to target well-defined tumors with unprecedented precision. SRS (stereotactic radiosurgery) is used to treat the brain and spine, and SBRT (stereotactic body radiation therapy) is used to treat structures other than the brain and spine. Because of the accuracy of the treatment, normal surrounding tissue is mostly spared, minimizing damage to healthy areas and decreasing side effects. SRT is used to treat tumors that would otherwise be considered inoperable or untreatable through traditional radiation therapy. It can be used to treat brain, nasal, and prostate tumors, mast cell tumors, osteosarcomas, and any tumors located near vital organs, which would otherwise be difficult to treat.
The entire radiation dose can be delivered in two or three sessions lasting less than 15 minutes each, greatly reducing the number of times a patient must undergo anesthesia. Treatment is usually completed within one week, resulting in 85-90% fewer treatments than is required with traditional radiation therapy, while providing increased efficiency and convenience.
Image-Guided Radiation Therapy
Image-guided radiation therapy (IGRT) is one of the most important innovations in cancer treatment. The slightest body movement, such as breathing, can cause the targeted tumor to move. IGRT allows for precise location mapping, tracking and treatment delivery.
Strontium-90 Plesiotherapy uses a dime-sized radioactive probe to deliver low energy beta radiation therapy to superficial tumors of the skin, eyelids, and ears, many of which are difficult to remove surgically. Side effects are rare because the radiation only travels to a depth of about 4 mm, thus avoiding underlying structures.
Some patients treated with Strontium-90 radiation therapy develop an ulceration which forms a scab and heals over time. These side effects rarely bother the patient.
Treatment is usually completed in one or two 5-10 minute sessions.
Palliative Radiation Therapy
Palliative radiation therapy is given to reduce the pain and swelling that accompanies some tumors. The goal of palliative therapy is not to cure the patient’s disease, but to improve the patient’s quality of life.
Not every patient benefits from this treatment, but those who do often experience improvements lasting two to four months or longer, and pain control may start within days of the first radiation dose. When symptoms of the cancer return, palliative therapy may be repeated for most patients who responded to the first course of therapy.
Definitive Radiation Therapy
Definitive radiation therapy is recommended for tumors that cannot be surgically removed without great risk or complications for the patient. Because the radiation passes through normal tissue surrounding the tumor, multiple small doses of radiation are given to maximize the damage to the abnormal cancerous tissue while minimizing the damage to the surrounding normal tissue. Conventional radiation therapy is mainly utilized for tumors that have tiny tendrils of cells extending from the tumor that are not possible to see with the human eye (microscopic disease) or with imaging. Cancers that are commonly treated with radiation alone include tumors inside the nasal passage, perineum and brain, and some soft tissue sarcomas. Depending on the location of the tumor, a CT or MRI and a computerized three-dimensional treatment plan may be used to plan the radiation treatment. Definitive radiation therapy is administered with the goal of achieving long-term control or cure of the disease. Treatment typically lasts three to four weeks and is often delivered on a Monday through Friday schedule.
Intensity-Modulated Radiation Therapy
Like conventional radiation therapy, IMRT uses multiple doses of small increments of high-energy x-rays to target a tumor, and is also usually given on a daily Monday through Friday schedule over a period of 3 weeks to 1 month. Like SRS and SBRT, IMRT is another complex and precise method of delivering radiation therapy that relies on detailed imaging and computerized three-dimensional treatment planning to obtain the accuracy needed to minimize radiation side effects.
Due to its precision, IMRT spares the surrounding normal tissue and is beneficial for tumors in the nasal cavity or regions where radiosensitive structures need to be avoided. The radiation oncologist determines if IMRT would be more beneficial than conventional radiation therapy or stereotactic radiation therapy.
What to Expect
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.