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Featuring Demian Dressler, DVM and Susan Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

CyberKnife RadioSurgery in Pets

Updated: December 18th, 2018

If you have been following me on Facebook at Dr. Sue Cancer Vet, you know that last week I was lecturing with what I call “ASC Team CyberKnife.” This team includes radiation oncologist Dr. Sarah Charney, neurologists Drs. Rick Joseph and Jason Berg, and me, the medical oncologist.  We manage all the CyberKnife patients that come to the Animal Specialty Center (ASC) in Yonkers NY.

So after work on two nights, we all traveled to Red Bank, NJ and then to Norwalk, CT to talk to veterinarians about CyberKnife RadioSurgery, what tumors it’s good for, and our experience over the last 4 years.

There is a lot of great information on radiation therapy in the Dog Cancer Survival Guide, but in case you haven’t read it yet, you should know that typically, radiation therapy is used for local disease control — to damage and ultimately kill the primary cancer, usually as a follow up treatment to surgery. For example, if a dog has an incomplete resection — which means that there are cancer cells detected in their surgical scar on the biopsy report (dirty margins) — we would follow the surgery with radiation treatments to “clean up” those microscopic cancer cells. This is pretty common when it comes to a mast cell tumor or a soft tissue sarcoma. These conventional radiation therapy treatments usually require fifteen to twenty treatments, which are also called fractions (see below). Each session requires a short anesthesia, and pets are usually treated daily Monday to Friday with the weekends off. That’s a lot of anesthesia.

Why SO many treatments? It’s all about the normal tissue in the radiation field.  To minimize damage to the normal cells, the dose is divided up into many small treatments. These “fractions” are helpful because normal cells can repair themselves more efficiently after smaller, multiple doses. For example, if your dog has a tumor in the nose, conventional radiation therapy will probably expose other nearby body parts to the harmful radiation: the mouth, eyes, and brain may get radiation because it is in the treatment field.

It’s this damage to otherwise healthy tissue that has motivated oncologists to look for a way to deliver radiation with more precision, fewer side effects, and fewer treatment sessions.  The new technique called radiosurgery aims at getting the radiation energy directly to the tumor – even inoperable tumors – while avoiding healthy body parts that might be damaged by the beam or by its scatter.

By the way, I personally think the radiosurgery name is silly because there is no surgery in radiosurgery. There is no actual cutting – the name is meant to imply that radiation is accomplishing what surgery would do if it could actually get to the tumor.

Radiosurgery is not good for every type of tumor (for example, mast cell tumors and soft tissue sarcomas are not good candidates). But it does offer hope to some patients whose tumors were once considered inoperable. Here’s why:

The new, modified linear accelerators (radiation therapy machines) can generate very controlled, narrow beams that deliver radiation very precisely. The machine has five “arms” and rotates around several axes. It can approach a tumor from almost any angle the radiation oncologist wants it to, and while a traditional linear accelerator has two to four ports (holes where the radiation exits), the CyberKnife has hundreds.

Planning the radiation is critical when you’re dealing with radiosurgery. First, a CT (computed tomography) scan is done to get a very detailed three-dimensional image of the tumor. (For brain tumors we need both a CT and MRI for planning.) Then, Dr. Charney, our radiation oncologist, uses a complex computer program to plan precise coordinates for the radiation beam.

The precision involved in radiosurgery is amazing, and it also makes radiation therapy more appealing to dog lovers. For example, a nasal tumor that requires fifteen to twenty conventional sessions and exposes the mouth, eyes, and brain to radiation can be treated in only three consecutive CyberKnife sessions. That’s five times less anesthesia, five times fewer trips to the hospital, and fewer side effects. And the results are comparable to traditional radiation therapy. Some brain tumors are treated in just one treatment. It is pretty amazing!

My practice was the first to offer CyberKnife Radiosurgery to animals, and we have been treating dogs and cats since March 2008. Currently, radiosurgery is only practiced at the University of Florida, Colorado State University, southern California, and my practice the Animal Specialty Center in New York.

In my next blog I will tell you what tumors we treat and our experience so far. Stay tuned – this is pretty exciting stuff!

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Leave a Comment





  1. Mike Calderon on May 29, 2019 at 7:45 am

    Any successful treatment of canine insulinoma in pancreas using cyberknife? Thanks.

  2. ann on May 16, 2019 at 7:42 am

    just curious re radiation and oral malignant melanoma. My dog is 13yr and second tumor has just had to be removed from inside lip (didn’t get clean margins)He had been on Oncept for just over a year after first tumor was removed successfully. From my research it looks like radiation would be hard on him for his age plus melanoma being so aggressive would probably show up elsewhere eventually. Please let me know what you think, am praying for right decision.

    • Dog Cancer Vet Team on May 17, 2019 at 7:44 am

      Hey Ann,

      Thanks for writing. When you’re unsure of what route to take, you should have a look at the section on Treatment Plan Analysis. Especially the articles on How to Make Decisions About Dog Cancer Treatments and Why Your Personality Is So Important To Your Dog with Cancer 🙂

      There is no “one-size-fits-all” treatment plan when it comes to dog cancer as each dog and their health situation is unique. You have to decide on a treatment plan that is right for both you and your dog. Are you okay with handling the side-effects of conventional treatments? How important is life-quality to you? Do you think your boy can handle surgery? These are just some of the questions that you have to ask yourself.

      Radiation is definitely not a walk in the park, and this why knowing yourself, and your dog, is so important when making treatment plan decisions. You should also check out this article on Things You Need To Know About Radiation for Dog Cancer and Chapter 11 of the Dog Cancer Survival Guide, which covers conventional treatments like surgery, radiation, and chemo 🙂

      Also in the Dog Cancer Survival Guide, Dr. D writes that there are a number of things that you can do to help your dog with cancer– under your vet’s supervision– such as conventional treatments, nutraceuticals, immune boosters and anti-metastatics, mind-body strategies and diet. This is what he calls Full Spectrum Cancer Care and you may find it to be helpful 🙂

      When you know what your options are and what is most important to yourself and your dog, you will be able to make a more informed decision. Don’t forget to consult with your vet or oncologist, and ask questions! 🙂

  3. Tom Liskowski on April 7, 2019 at 10:20 am

    My dog Max has a nasal tumor and was treated in MedVet Chicago with Cyber knife.He had 3 consecutive days of radiation last week.How long does it take before the treatment begins to help.He seems about the same ,sneezing ,snoring.Does it take a couple weeks before the radiation starts to work?Thanks

    • Dog Cancer Vet Team on April 8, 2019 at 6:28 am

      Hey Tom,

      Thanks for writing, and we’re sorry to hear about Max. That’s a tough question, and one best left to your vet or oncologist. As we aren’t veterinarians here in customer support, we can’t offer you medical advice.

      However your vet can. You have to remember that your vet knows your dog, they know the treatment plan, and they are able to physically examine Max. They can provide you with information that is based off of your particular boy, and his treatment plan. So they are the best person to ask for a better-informed answer 🙂

  4. Ellen Schlegel on December 27, 2018 at 12:03 am

    Why is stereotactic radiation not goodFor treating soft tissue sarcoma???

  5. Jane on December 6, 2018 at 8:06 am

    Why is stereotactic radiation not good with mast cell tumors?

    • Molly Jacobson on December 10, 2018 at 3:04 pm

      Hi Jane, thanks for your question. I’m not a veterinarian, so I’m not sure I have the right answer for you, but as the book editor, my guess is that mast cell tumors change too often and are too “tricky” for such an expensive treatment that depends on knowing EXACTLY where a tumor is in the body. Mast cell tumors can grow overnight or shrink and seem to disappear in an hour — they are the “tricksters” of tumors. I suspect that these tumors are difficult to plan for in the way this type of radiosurgery requires. Remember, it’s not just radiation — it’s also “surgery.” Where you place that radiation beam really matters, and they better know for sure there is a tumor there!

  6. […] turned out to be a life saver! The one option that the teaching hospital could not offer was cyber knife treatment – targeted intense radiation – which was available through Hope Veterinary Specialists […]

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