Retrievers: The Silent Killer

A friend of mine recently had to make the gut-wrenching decision to put down his wonderful golden retriever in the prime of its life. The diagnosis was hemangiosarcoma, an aggressive cancer of the blood vessels that can strike at any age and often goes undetected until it’s far too late for treatment. It’s for this reason that the disease, which accounts for one in five of all golden retriever deaths, earned the nickname “the silent killer.”

Hemangiosarcoma may be the deadliest and most insidious type of cancer to which the golden is susceptible, but it’s far from the only one. Others include osteosarcoma, lymphoma, and mast cell tumors. Slightly more than 60 percent of golden retrievers will develop cancer during their lifetimes, compared to the baseline canine cancer rate of around 25 percent. Labs are also considered high-risk for these malignancies, although not to the degree that goldens are.

Lifestyle and environmental factors that influence cancer risk have only begun to be studied in dogs. Still, a few salient findings have emerged. One, not surprisingly, is that obesity is linked to an increased risk for certain cancers—yet another reason to maintain your dog’s healthy lifestyle and keep him from packing on extra pounds.

With respect to environmental exposures, there’s evidence that many of the same compounds that are linked to cancer in humans can also be risk factors for canines. The science is in its infancy, but according to Dr. Lauren Trepanier of the University of Wisconsin School of Veterinary Medicine, “One of the things that’s already raising red flags for an increased risk of lymphoma is benzene, which is present in cigarette smoke. So we can say pretty confidently that if you have a dog with a high ‘breed risk’ for lymphoma, like a golden retriever, you shouldn’t be smoking or allowing smoking in your home.”

Noting that certain types of broadleaf weed killers are “strongly associated” with canine bladder cancer, Trepanier is also adamant that you shouldn’t use herbicides on your lawn. Nor, she says, should you walk your dog in areas that have recently been treated with weed killers.

Since the early 2010s, Drs. Benjamin and Lynette Hart of the UC Davis School of Veterinary Medicine have been studying the long-term health effects of spaying and neutering. Their research led them to the startling discovery that spaying a female golden retriever, at any age, increases her risk for developing cancer by a factor of three to four. Describing this finding as “unique to the golden retriever,” they recommend that female goldens not be spayed. If you’re the owner of a female golden, keeping her “intact” is probably the single most proactive step you can take from a cancer prevention standpoint. This is not without its own risks, of course, so you should discuss the pros and cons with your veterinarian.

Not every case of cancer can be prevented, of course, which brings us back to hemangiosarcoma. While significant strides have been made in the diagnosis and treatment of other canine cancers, “the silent killer” has been stubbornly resistant. Now, thanks to a pair of clinical trials funded in part by the American Kennel Club’s Canine Health Foundation, there’s a glimmer of hope on the horizon.

At the University of Florida College of Veterinary Medicine, Dr. Rowan Milner has seen extremely promising results from a therapeutic vaccine that, by attacking a specific molecule on the surface of hemangiosarcoma cells, stimulates the immune system to attack. And at the University of Minnesota College of Veterinary Medicine, Dr. Jaime Modiano and his team have achieved what he describes as “probably the most meaningful advance in treating canine hemangiosarcoma in over 30 years.” Using an experimental blood test that detects hemangiosarcoma cells much earlier than is typically the case, combined with a novel treatment that targets the cells where the disease originates, the six-month and one-year survival rates of affected dogs were “significantly” improved.

It’s still early days, and much work remains to be done. But it’s finally possible to imagine a future in which retriever owners won’t have to face the kind of terrible decision that my friend did.