A (Gamma) Ray of Hope: Veterinary Cyberknife Shows Promise for Pets with Cancer

cyberknife

Darlene Cook wasn’t expecting a cancer diagnosis when her 10-year-old Golden Retriever Liberty (Libby) began limping. Because Libby had tested positive for Lyme disease in the past, Cook — herself a veterinarian — suspected her dog had relapsed. But MRIs of Libby’s chest, abdomen and bones revealed a different story: Libby had a localized bone cancer called an osseous plasmacytoma, and surgery was not an option.

“Because it is such a rare cancer, we didn’t have a lot to go on,” recalls Cook, “but the recommended treatment was radiation therapy. The original plan required 22 treatments, Mondays through Fridays, at the [nearby] University of Minnesota.”

After the third day of treatment, Cook saw a red flag. “One of the risks of radiation is the anesthesia and intubation necessary to administer the treatment. Some animals develop a cough after intubation that can turn into pneumonia. Libby started coughing on the third day. That concerned me because she still had considerably more treatments to go.”

Libby’s luck changed when Cook heard of a cutting-edge treatment called veterinary cyberknife, which can deliver an entire dose of radiation in one to three treatments (versus 20 or more with traditional radiation). When Cook learned that Libby’s treatments could be significantly reduced, she packed up and drove 17 hours from Minnesota to the Veterinary Cyberknife Cancer Center near Philadelphia, PA, to pursue it.

no bones about it

Libby’s inoperable bone tumor made her a perfect candidate for cyberknife radiation, according to Dr. Siobhan Haney, VMD, MS, DACVR (RO) at the Veterinary Cyberknife Cancer Center. “If there are any areas of uncertainty — like when 99% of a tumor is removed by a surgeon but some cancerous cells remain — a much larger field of radiation is needed to blanket the area, and that’s when conventional radiation is ideal,” says Dr. Haney. “But when there’s a physical tumor visible to the naked eye or via MRI, we can target that tumor exactly with a large dose of cyberknife radiation.”

Why the difference? Cyberknife radiation is delivered via an “intelligent” arm so accurate it can target the cancer within a 1-5 millimeter tissue margin. Conventional radiation delivers the treatment over a much broader field of 20-30 millimeters.

This accuracy is significant because cyberknife targets only the cancerous cells, and spares the healthy organs and tissue surrounding a tumor from damage. Because the risk of harming healthy cells is virtually nonexistent, cyberknife can administer a much stronger dose of radiation, which means the entire course can be delivered in fewer treatments.

Osteosarcomas like Libby’s are one of the most frequent types of cancer Dr. Haney treats at the Center, which is connected with HOPE Veterinary Specialists in Malvern, PA. “Bone tumors are tough to treat and there’s generally a poor prognosis associated with them,” says Dr. Haney. “Traditional radiation gives pets an average of maybe two to four months of survival time. With cyberknife, we’ve seen pets survive six to 12 months. Not only can this make a huge difference to the pet owner, but the dogs are more comfortable because the side effects are so minimal.”

on the safe side

“A lot of people don’t want to take the first step to talk to a veterinary oncologist because the words ‘chemo’ and ‘radiation’ scare them,” says Dr. Pam Lucas, DVM DACVIM (Oncology) at South Carolina Veterinary Specialists & Emergency Care. “But the goal of treatment is quality of life for an animal, so most treatments don‘t have the side effects people go through. There are very few cancers that we cure, but even a one-year survival time equates to about five years for a human – most people don’t think about that. Cyberknife takes it one step further for preserving quality of life.”

Typical side effects of conventional radiation therapy for pets include burns to the skin, swelling, ulcers, nosebleeds and lethargy, among others; cyberknife virtually eliminates these. “When we treat nasal tumors we might see a little hair loss on the bridge of the nose, and skin can turn darker where the radiation is aimed,” says Dr. Haney. “About 10% to 15% of patients being treated for brain tumors experience a little swelling in the brain – which sounds serious, but it’s actually not. We treat the swelling with steroids and it gets better in a day or two. It’s a significant improvement over conventional radiation. There’s less medication and less need for follow-up care. It makes a pet’s life a thousand times better.”

“I think cyberknife is going to dramatically improve the quality of life for sick pets because it spares critical structures like the eyes, ears, mouth and back of the throat from damage,” says Dr. Lucas. “For senior and geriatric pets, you worry about long courses of radiation because of the amount of anesthesia required, but with cyberknife you get the same benefit without as much strain on other vital organs like the heart and kidneys.”

a rapid response

Dr. Haney says patients often show signs of improvement after the first or second treatment. For Libby, the cyberknife radiation improved her symptoms almost immediately. “She was limping when she came in [to the Center], but by the third day of treatment her limp was barely perceptible and her cough was gone,” says Cook. “She has continued to do well. She’s playing ball, chasing squirrels – you’d never know she had cancer.”

The rewards of cyberknife radiation can be great, especially in treating one of the most frightening cancers: brain tumors. “You can have a dog or cat who presents with severe clinical signs like circling, compulsive behaviors or aggression,” says Dr. Lucas, “but with appropriate therapy the prognosis can be bright. Clients sometimes come in with a debilitated pet but after radiation it’s like a light switch goes off and suddenly they have their old pet back again.”

clearing the hurdles

If there is one drawback to cyberknife, it is that the technology is so new to veterinary medicine that it isn’t yet widely available. The Veterinary Cyberknife Cancer Center is one of just two facilities in the U.S. offering the treatment, and for many pet parents the $5,000 to $9,000 price tag — plus the burden of travel — can be prohibitive.

“I’ve been doing my best to spread the word to clinics that see a lot of cancers so they know there is now an additional option for treatment,” says Cook. “I also promote pet insurance to my clients. When the time comes and there’s a costly decision to be made, pet insurance takes money out of the equation.”

Dr. Lucas agrees. “Many clients can’t go out of pocket for these advanced treatments because most of them don’t have pet insurance,” she says. “This is one of the reasons we advocate for it so much.”

future perfect

While it is still early to determine the full effect veterinary cyberknife can have on treating cancer in pets, so far we know it is at least equivalent to conventional radiation in terms of survival times. The reduced number of treatments and fewer doses of anesthesia could mean that in time veterinarians will be able to escalate the radiation dose for a potentially better outcome.

“Right now we are on the cusp of a really exciting time in veterinary oncology,” says Dr. Lucas. “In the next five to 10 years, I think we’ll see more treatments [like cyberknife] become available.”

“Our experience so far has been fantastic,” says Dr. Haney. “It’s not a cure, not a magic bullet, but it is a better treatment that allows pets to return to quality of life.”
Looking at a dog like Libby, whose age and type of cancer could have made her treatment both rough on her physically and risky for her health, cyberknife seems to hold a lot of promise.

“It is important to know that there is hope,” Dr. Haney continues. “A lot of times cancer is so negative; people have preconceptions about what treatment is like, but there are options out there. There are options and there is hope.  We value quality of life over anything. There are so many more things available today than even five years ago.”

[SIDEBAR]

pins and needles

For many four-legged cancer patients, successful treatment integrates traditional and alternative therapies. According to Dr. Haney, cyberknife radiation often pairs well with acupuncture – in fact, two of the Center’s staff members are also certified veterinary acupuncturists. “The good thing is the animals are already under anesthesia [from the dose of radiation], so administering acupuncture is easier and the needles can stay in longer – it takes that variable of worrying about the animal moving out of the equation.”

Here’s how a few pin pricks can perk up pups undergoing cancer treatment:

  • relieve pain
  • stimulate the appetite
  • boost immune function
  • restore energy levels
  • increase serotonin and endorphin levels
  • minimize GI discomfort
  • increase blood circulation
  • raise white blood cell count (especially important for pets receiving chemotherapy)

— published in fetch! magazine, the “Golden Oldies” issue

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