Stereotactic Radiation Therapy for Dogs

When Stereotactic Radiation Therapy for Dogs is Recommended

If available in your area, your veterinarian or veterinary oncologist may recommend stereotactic radiation therapy for dogs with tumors that cannot be removed surgically or are hard to reach.

It may also be recommended for tumors that are near or part of vital organs (ex: heart base tumors, brain tumors, etc.).² Stereotactic radiation is more precise than conventional radiation, so it is less likely to damage these delicate and important tissues.

You can also opt for stereotactic radiation even if your dog could benefit from conventional radiation. The smaller number of treatments and lower risk of side effects is very attractive for many dog lovers.

How Stereotactic Radiation Therapy for Dogs Works

In general, radiation therapy involves sending ionizing radiation into a tumor to cause damage to the DNA and other molecules in the cancer cells.¹ It will also damage non-cancerous cells in the field of the radiation.

Traditional fractionated radiotherapy uses a high total dose of radiotherapy that is split up into many smaller doses typically over the course of 3-4 weeks.

Stereotactic radiation therapy (SRT) uses an overall smaller dose of radiation, however it is given in fewer visits with higher doses given per visit.

SRT is also different because it uses advanced imaging and robotics to precisely line up the radiation equipment to ensure that the radiation is delivered to a highly specific area, thus saving as much non-cancerous tissue as possible.⁵

Cancers SRT Is Commonly Used For

• Brain tumors^1,2,6
• Bone tumors including osteosarcomas (this is typically just for pain control/palliative care)⁷
• Nasal tumors^1,2,8
• Multilobular osteochondrosarcoma^1,9
• Pituitary tumors^1,3
• Thyroid tumors^1,10
• Heart base tumors^1,11
• Mast cell tumors¹²
• Soft tissue sarcomas¹³
• Tumors in the pelvic canal^1,2

Common Examples of SRT

Prescriptions for radiation therapy are written as the number of fractions (the number of doses) of the amount of radiation given. Radiation is measured in Gray (aka Gy). For example, 5 doses of 4 Gray would be written as 5Gy x 4 Fractions.

• Example: Pituitary tumors: 15 Gy x 1 fraction or 8 Gy x 3 fractions³
• Example: Nasal tumors: 9-10Gy x 3 Fr4

The most important thing for you to know is the number of fractions your dog will be receiving, as this is the number of days you need to bring her in. But if you’re interested, the oncologist can absolutely walk you through your dog’s total planned radiation dose and the dose for each fraction.

What Happens During Stereotactic Radiation Treatments

• Your dog will be taken into the hospital for advanced imaging (typically a CT scan) under anesthesia to image the tumor completely.
• Radiation oncologist takes imaging of tumor and creates a stereotactic radiation plan using specialized software.
• On actual treatment days, your dog will undergo anesthesia, and the treatment is performed. Typically, 1-5 treatments are given within 1 week.
• The treatment consists of specialized equipment sending beams of radiation to the tumor from different positions with the maximum amount of radiation hitting where the beams intersect (in the tumor) and minimal radiation hitting the areas of normal tissue.
• Once the procedure is over, your dog is allowed to wake up from anesthesia. Once they have recovered from the anesthesia, they either go home for the evening or stay in the hospital for the night.^1,2

How to Get the Best Results

Since the procedure is performed under anesthesia, it is recommended that dogs are fasted on the morning of SRT.

After radiation therapy, avoid exposing the skin to excess sunlight or applying creams or lotions as this can cause more irritation.

There is mixed evidence about the use of antioxidants with radiation therapy. Theoretically, antioxidants (vitamins A, C, and E, silymarin, etc.) help repair cells from radiation-induced damage, however they may also help cancer cells in the same way.

In general, most radiation oncologists recommend refraining from taking supplemental doses of antioxidants during radiation therapy.^14,15,16

Home Care

After your dog has completed their radiation treatments, you will likely be sent home with pain medications and/or anti-inflammatory drugs to help with side effects.

It is very important that you do NOT apply any ointments or creams to the skin that may be inflamed without consulting your radiation oncologist first. Many ointments and creams can make radiation side effects worse.

Many general practice veterinarians are not familiar with post-radiation care, so it is vital that you discuss this with the radiation oncologist.

Most dogs will just need some pain medication, time, and an e-collar (cone) to prevent scratching. Some dogs will benefit from soft food if the radiation therapy was performed near their mouth.¹⁷

Follow Up

Recheck appointments will be recommended to you by the radiation oncologist based on your pet’s specific condition and treatments, however imaging is typically repeated every 6 months afterwards or as recommended to monitor for regrowth.

Rechecks may be needed to manage side effects.¹

When to Not Use Stereotactic Radiation for Dogs

Stereotactic radiation cannot be used if there is no visible tumor present on imaging. For example, tumors that have been removed but without clean margins are not candidates for stereotactic radation.

It is also not typically used for tumors that have metastasized (spread to other parts of the body) unless it is used alongside chemotherapy.¹ While the SRT will target the primary tumor, the metastases will not be within the radiation beam.

Caution should be taken with SRT for heart base tumors. If they are slow growing and not causing problems for the dog, SRT may not be the best approach since it may cause life-threatening arrhythmias.¹¹

Acute and late side effects can be worsened if radiation therapy is used in conjunction with some other cancer treatments including: doxorubicin, dactinomycin, fluorouracil, methotrexate, bleomycin, nitrosoureas, and etoposide.¹⁸ If your dog is receiving any of these drugs, radiation therapy may not be appropriate.

Where to Get Stereotactic Radiation

Stereotactic radiation therapy is available only at specialty veterinary hospitals with radiation oncologists. The necessary equipment to perform this type of radiation is extremely expensive and requires a lot of safety measures to protect staff, so many facilities do not offer this treatment.

To find a hospital that can perform radiation therapy visit vetcancersociety.org/pet-owners/find-a-vcs-member/ Some of these locations may not offer SRT specifically.

Stereotactic Radiation for Dogs Side Effects

Side effects depend on the area of the body undergoing radiation therapy. With stereotactic radiation therapy, there should be fewer side effects compared to conventional fractionated radiation therapy, however, side effects are still seen.

These can be divided between acute (short term) side effects and delayed/late (long term) side effects.²

Acute Side Effects

These typically occur at the time of radiation therapy or shortly after.

• Affect rapidly dividing tissues (skin, intestinal lining, oral mucosa, etc.).
• Typically self-limiting and do not require extensive treatment other than pain management and supportive care.
• Examples include erythema (redness of the skin), oral mucositis (ulceration of the oral cavity), arrhythmias (if treatment is for heart base tumors), etc.

Delayed/Late Side Effects

These occur months to years after treatment and are less common, but often more severe.

• Damage to the slowly proliferative tissues (bone, lungs, heart, kidneys, nervous system).
• Difficult to treat.
• Examples include fibrosis, necrosis (tissue death), organ failure, fistula formation, strictures, cancer, etc.
• Should occur in less than 5% of patients over the course of 5 years after treatment.

Stereotactic Radiation for Dogs Cost

The cost will depend on the hospital, but estimates are around $6,000-10,000 depending on the specific treatment.

Additional follow-up imaging (CT scans) range between $1500-3000 depending on location, and additional hospitalization or treatment costs may be present if there are side effects.