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Advancing cancer treatment
A Q&A with small-animal oncologist specialist Dr. Stephen Withrow


DVM: How are the trials funded?

Withrow: We've been able to get some funding from sources that normally fund human medicine, such as the Bill and Melinda Gates Foundation. We're doing a nutrition intervention study with rice and beans that could alter the course or side effects of disease in humans. We're studying the influence of this diet on dogs and cats. The Gates Foundation wants to know if these data are transferrable to people in third-world countries. We also get some funding from the Morris Animal Foundation, which gets its donations mostly from pet owners who want to make an impact on certain diseases. The NIH, pharmaceutical companies and private individuals fund our other studies.

DVM: What types of cancer surgery tend to have the best and worst outcomes and why?

Withrow: The best outcomes are in patients whose cancer is localized and we've done aggressive removal in portions of the jaw, shoulder blade, rib cage and so on. This is where surgery has its role. But some surgeries are only one part of the treatment, and the patient needs a combination of therapies. For example, I might remove 99 percent of the tumor and the rest is treated with radiation or chemotherapy. We also have good surgical outcomes with mast cell tumors and breast cancer—but with a disease like hemangiosarcoma, not so much.

DVM: Any cancer prevention tips you can offer?

Withrow: I wish I knew! Less than 10 percent of animal cancers can be attributed directly to a heritable genetic cause. Cancer in animals is a multifactorial disease. Prevention, I'm afraid, is the elusive Holy Grail. By the way, that's not the case in human medicine. In humans, we know that if you reduce obesity or don't smoke you reduce the incidence of certain cancers. I suppose we could say that in some environments where ultraviolet light is high, light-pigmented or white dogs should get only limited time in the sun.

One thing in particular that's the single best way to prevent cancer in pets—spaying and neutering. If you spay a dog before she's 1 year old you can go a long way in preventing her from getting breast cancer. And in male dogs, you can reduce the risk of cancers of the reproductive system. With spaying and neutering there's a reasonably straightforward cause and effect.

DVM: To help detect early development of cancer in pets, what are some signs clients should watch for?

Withrow: We worked with the Veterinary Cancer Society to put together a list, which readers can find online. [Editor's note: The list is available at]

DVM: Are there any promising new cancer treatments down the road?

Withrow: Yes. In the last 10 years, there's been a tremendous body of literature examining how cancer develops, how it escapes detection in the body, what cancer cells depend on to grow and much more. The most exciting thing to come out in recent years is the research on targeted pathways to prevent tumor growth. The haystack of information available today is just immense. It's finding the needles that can guide better therapies—that's still the hard part.

That said, the first two licensed drugs for animal cancer were recently released. They're molecularly targeted treatments that work on mast cell cancers, which are common skin tumors in dogs. The drugs are Palladia from Pfizer and Kinavet made by AB Science. While that's a terrific start, we have 200 different cancers to treat. We need help from our chemotherapy colleagues.

DVM: Any final thoughts on the topic of small-animal oncology?

Withrow: It's refreshing to see all of the oncology training and education programs available now, the quality of the care patients get, the availability of referral services and specialized veterinary care and how the private sector and clients have embraced veterinary oncology. Pet owners today are more engaged with their pets and willing to pay for these treatments to save their beloved animals.

DVM: I hear you're looking ahead to retirement. What do you plan to do when you have more time on your hands?

Withrow: I recently stepped down from the director's position at ACC and am now the associate director. Dr. Rod Page is the new director, and the transition has been seamless and exciting for me. That's freed up some time. I like fundraising for the ACC and probably will continue doing that. I will continue to teach surgical oncology and do research.

Loyle is a freelance medical editor and writer in Philadelphia and the former primary editor of the North American Veterinary Licensing Examination.


Source: DVM360 MAGAZINE,
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