Radiation Oncology

Veterinary radiation oncology is a medical specialty that involves the concise use of external beam radiation to treat cancer either for long-term control, or to reduce pain and other symptoms caused by cancer.

 

Radiation Therapy

In veterinary medicine, radiation therapy was first attempted at the beginning of the twentieth century. During the past 50 years, major advances have been made. The use of histopathology, MRI, and CT scans has resulted in a more specific understanding of tumor behavior based on tumor type and location. Newer radiation equipment and new technology such as intensity modulated radiation therapy (IMRT) has allowed radiation delivery to be tailored to the individual patient’s tumor with more and more accuracy. This has increased the effectiveness and decreased the side effects and risks of radiation therapy.

Stereotactic Radiation (SRT) & Intensity Modulated Radiation Therapy (IMRT)

Stereotactic radiation (SRT) and Intensity Modulated Radiation Therapy (IMRT) are becoming more readily available for family pets and other exotic animals. In the past, traditional radiation therapy to treat cancer in pets would usually result in significant side effects and many owners would decide not to pursue treatment after learning of the short term and long term ramifications. Favorably, IMRT and SRT are changing the way that we are able to treat cancer in pets, and they have great potential to improve both your pet’s quality and quantity of life.

Our hospital is equipped with state-of-the-art instrumentation, including the Varian Halcyon Linear Accelerator capable of delivering stereotactic radiation therapy. Stereotactic radiation delivers precisely focused radiation beams to treat tumors while sparing normal tissues. Stereotactic radiation uses advanced 3D imaging to target high doses of radiation to the affected area with minimal impact on the surrounding healthy tissue. Stereotactic radiosurgery is often used to treat tumors of the brain and spinal cord, providing a beneficial therapeutic option for non-surgical tumors. Stereotactic Body Radiation Therapy (SBRT) is used to treat all other regions outside the brain and spinal cord and is typically completed in as few as 3-5 treatments.

Half-Body Radiation

Most dogs with lymphoma will go into remission after only a few chemotherapy treatments and they will often stay in remission for months. During this time, aside from having to come to see the oncologist for treatment, their quality of life is often very good. Once they go into remission, owners often report that they are running, playing, or just living their normal life as if they never had cancer. Unfortunately, almost all of these pets will eventually come out of remission and succumb to their disease. In the past twenty years there has been little to no improvement in the remission and survival times with chemotherapy alone. With this protocol, dogs are first treated with chemotherapy to get them into remission and this is followed by two treatments of half body radiation. They can get some changes to their hair coat and some intestinal upset, but otherwise they are typically fine. Most dogs will then go on to complete a shortened chemotherapy protocol. Initial results suggest that by combining radiation therapy with chemotherapy in this way, dogs remain in remission longer and continue living longer with lymphoma.

Unfortunately, at this time, we are not offering half-body radiation therapy at The VCC. However, we will gladly provide the names of radiation centers nearby capable of such protocols.

Radiation Oncology FAQs

Service FAQs

Radiation therapy can be used alone or in combination with surgery and/or chemotherapy to damage the tumor cells or provide long-term control of the tumor. In the majority of pets, we are focusing on localized tumors and regional disease control in cancer patients that have no evidence of spread to distant sites in the body (e.g. lungs or liver). In other cases, radiation therapy can be used for its palliative effects (relieving pain or other signs of disease). Even if the tumor cannot be destroyed completely, radiation may result in rapid pain relief and may shrink the tumor or slow down tumor growth. This often will improve the quality of life of the pet.

Tumors that are commonly treated with radiation include oral tumors, nasal tumors, brain tumors, nasal tumors, mast cell tumors, soft tissue sarcomas, bone tumors and many more. However, radiation can be used to treat almost any localized tumor and it is sometimes used to treat widespread cancers. Many times, radiation will be used postoperatively if the tumor cannot be removed completely. This is commonly done for soft tissue sarcomas, mast cell tumors, and other superficial tumors. Also, radiation can often be an effective treatment for tumors when surgery either is not possible because of potential risks during the surgery or concerns for postoperative complications. For example, tumors in certain locations in the brain may best be treated with radiation alone.

If your pet is a candidate for radiation and you decide to go ahead with treatment, your oncologist/radiation oncologist will discuss the number of treatments your pet will need and the potential side effects that you should expect. A planning CT scan will be needed prior to radiation, even if your pet has had an MRI or CT scan already. This scan is done with your pet in a positioning device that will be used for each future treatment. The CT scan is then used to develop a radiation plan that is customized to the tumor’s shape and location, to treat your pet successfully with as few side effects as possible.

For each treatment, your pet will need to be placed under general anesthesia to make sure that he or she stays perfectly still for the treatment. Although there is always a risk any time a pet is placed under anesthesia, the anesthesia for radiation is typically very short and short-acting drugs are used, so potential complications are rare.

Side effects of radiation for your pet will depend upon the dose of radiation used to treat the tumor and also the type of radiation that is used. With definitive radiotherapy (a daily treatment protocol), the normal tissues around the tumor will often develop redness and irritation at the end of the treatment protocol or after treatments have been completed. Newer radiation technology allows us to minimize these side effects in most patients. However, pets who are likely to develop significant side effects will often require pain medications or anti-inflammatory medications. Your oncologist/radiation oncologist and your regular veterinarian will work as a team to keep your pet as comfortable as possible. These side effects are almost always temporary and the goal in these situations is to get your pet through the side effects and back to having a normal or improved quality of life after the treatment. Additionally, there can also be a low risk of a long-term, permanent side effect from radiation. Fortunately, these side effects are rare and your oncologist/radiation oncologist will discuss these with you before starting treatment.

Usually your pet will need to have food and water taken away prior to each treatment, but your pet’s doctor will discuss the specifics of the fasting schedule. If your pet gets groomed on a regular basis it may be a good idea to have them groomed prior to radiation. Once the radiation starts you may not be able to have your pet bathed or groomed because there will be marks on their skin that cannot be removed.

Following radiation therapy, side effects may occur for up to three weeks if your pet is among those who develop them. Your oncologist/radiation oncologist will work with you and your pet’s regular veterinarian to manage your pet’s comfort level and medications. A side effect recheck exam is typically recommended in one to two weeks to make sure that the healing process is going well. After side effects are healed, your pet also should have routine recheck exams to monitor for regrowth of the tumor or for potential late side effects from the radiation. A plan will be discussed to have these rechecks alternate between the VCC and with your pet's regular veterinarian.

Stereotactic radiation, also known as stereotactic radiosurgery, involves delivering a small number of large radiation doses to the tumor, in the hope of causing maximal tumor damage while limiting the dose to the normal tissues. Usually this is done in 1 to 3 treatments over a short period of time. With stereotactic radiation, a large number of beams are directed at your pet from all different angles and the shape of the radiation beam is changed during treatment to deliver radiation where it is needed most.

SRT can be used to treat a variety of tumors, including brain tumors, pituitary tumors, nasal tumors, and other tumors involving the head and neck. It also can be used to treat tumors of the spine and some parts of the abdomen or chest. It can be used for pets when daily visits and anesthesia may be too risky.

IMRT uses the same technology as SRT with a large number of beams to attack the tumor from all angles and each beam is shaped to precisely deliver the radiation where it needs to be directed. With IMRT, similar doses are used that have been used for conventional radiation in the past. However, IMRT allows the dose of radiation to be targeted at the tumor, with great precision, to avoid treatment of the normal tissues. This allows the same or higher doses of radiation to be delivered directly to the tumor, with fewer side effects for your pet.

IMRT can be used to effectively treat nasal tumors, brain tumors, pituitary tumors, anal sac carcinomas, and a number of other tumors. In any location where radiation side effects might be a problem, IMRT can be used to help minimize them.

If your pet with cancer has already had a CT scan or an MRI to diagnose the tumor, he or she may need a second CT scan for radiation planning. The first CT or MRI is useful to help determine where your pet’s tumor is, but the radiation planning CT is necessary for your pet to receive treatment. With newer radiation technology, as we tighten, or conform, the dose around the tumor, it is critical that your radiation oncologist know exactly where they are treating. Therefore a second CT scan is often necessary for this. Usually, your pet will be placed in a positioning device such as a bite block and/or vacuum bag, to make sure that they are positioned the exact same way for the CT scan and for each treatment. The CT scan requires a short anesthesia, but it is well worth it to make sure that your pet is receiving the most accurate delivery of their radiation dose.

One of the main benefits of IMRT and Stereotactic radiation is that they can minimize the side effects from radiation, making treatment much more tolerable for you and your pet. With traditional radiation treatments there are often significant side effects in the local area from damage caused by the radiation. With IMRT and SRT, the dose of radiation can be targeted very tightly around the tumor using a radiation plan that is customized for your pet. This minimizes the dose of radiation that is given to your pet’s normal tissues. In some areas, such as the head or pelvis, this is critical for avoiding severe side effects. For example, traditional conformal radiation for nasal tumors in dogs usually results in severe inflammation and burning in the mouth, around the eyes and the skin of the face.

There is also a risk of a severe, long-term complication in the eyes, the brain or the local bones. With IMRT and SRT, the dose of radiation to these structures can be minimized, limiting side effects to small areas. This means a better quality of life for your pet. With any type of radiation treatment, a brief anesthesia is usually required. Anesthesia is needed to make sure your pet stays perfectly still for each treatment. It is usually a short anesthesia, and your pet is monitored very closely while receiving it.

Even when radiation patients have anesthesia every day, the risk of significant complications is very low. Your radiation oncologist will evaluate your pet to make sure that he or she is likely to handle the anesthesia well and may recommend additional staging tests, such as radiographs, ultrasound, an echocardiogram, bloodwork, and/or urinalysis to help make sure that your pet is a healthy candidate for anesthesia. Another potential benefit of SRT is that it may be able to limit the number of treatments that your pet will need, minimizing the risk of anesthesia complications.

If your pet has been diagnosed with cancer, and you want to learn whether IMRT or stereotactic radiation would help, consider making an appointment to meet with our radiation oncologist. We will evaluate your pet, review his or her medical records, and speak with you about what type of treatment options are available and best for your pet.