Penn’s veterinary hospital not only offers treatments that can prolong quality of life when a pet gets cancer, but also conducts research that sheds light on the disease in humans.
By Kathryn Levy Feldman

My 20-year old son found the lumps. He had been playing with our Lassie look-alike, Bentley, when he felt two masses almost the size of tennis balls under his neck.

“Mom, you better take a look at this,” he called.

“Oh, they’re probably nothing—just another one of his skin infections,” I said lightly after my inspection of our dog, who was then seven years old. “I’ll call the vet just to be sure.”

Even as I dialed the phone, I knew in my gut that it was not good. At Bentley’s appointment later that week, our vet confirmed my worst suspicions.

“They feel like lymphoma,” she said in her characteristic no-nonsense style. “I think we should do a biopsy as soon as possible.” Almost as an afterthought, she added, “I’m sorry.”

So began our family’s roller coaster ride with canine cancer, a shaky journey, at best, on which, I soon discovered, we have a lot of company. Cancer is the leading cause of death for dogs, killing 26 percent, and it accounts for almost half of deaths each year in animals over the age of 10.

Those figures may be just the tip of the iceberg, according to Dr. Karin Sorenmo, section chief of the oncology department at Penn’s Matthew J. Ryan Veterinary Hospital. “We are seeing the same thing in veterinary medicine as we are in human medicine, that the incidence of certain cancers is increasing,” explains Sorenmo, who is also assistant professor of oncology at the School of Veterinary Medicine. “And since not all companion animals who are diagnosed with cancer receive treatment, we may, in fact, be underestimating the prevalence of the disease.” She estimates that the hospital’s oncology department had about 2,800 patient visits last year. “There is most definitely an increased demand for our services.”

There are numerous reasons for the cancer increase in dogs and cats, not the least of which is longevity. Like people, companion animals are living longer due to better nutrition, preventive medical care, and quality of life. The longer an animal lives, according to Sorenmo, the more likely it is to develop cancer. “Cancer is a disease of the aging.”

Sorenmo also speculates that perhaps 80 percent of all cancers are environmental. For example, studies have linked higher rates of cancer in dogs and cats with sharing a home with smokers. Certain types of commercial lawn care are associated with an increased risk for lymphoma in dogs and cats, just as the use of certain herbicides and pesticides has been linked to a similar risk in humans who are farmers, Sorenmo notes. “We also see more bladder tumors in animals that live in or near swamps, and white cats that live outside are at greater risk for skin cancers,” as are dogs with white hair and thin skin.

Researchers have also discovered that certain breeds of dogs are more susceptible to the disease than others. In a 2001 study at Penn’s veterinary hospital, 56 percent of all golden retrievers and 52 percent of all boxers who died there were found to have died from cancer. “Cancer is more common in golden retrievers than in any other type of dog,” Sorenmo reports. “Whether this is true because golden retrievers are an extremely popular breed and there are simply more of them, we don’t know.”

Other breeds with a notably high incidence of cancer include Rottweilers, Bernese mountain dogs, Boston terriers, English bulldogs, Scottish terriers and Cocker spaniels. Bentley’s breed, collies, have a relatively low incidence of cancer. All of which proves that you never know.

Like us, most pet owners first learn of their animal’s cancer in their local veterinarian’s office. In the initial stages of the disease, most animals don’t seem sick and many tumors are detected as part of routine examinations. The next step is an accurate diagnosis, which usually involves a biopsy.

In Bentley’s case, our vet removed a lymph node from his hind haunch and sent it to the lab. When the result indicated lymphosarcoma, she referred us to Ryan Hospital’s oncology department for staging and treatment. By the time we got Bentley to Penn (about a week after his biopsy), he had developed a significant bacterial infection at the incision site (which was swollen and oozing, despite oral antibiotics) and was very weak and lethargic. He was barely eating (grilled hamburger and bacon seemed to be the only things we could get him to swallow, and they wreaked havoc on his digestive system), and he could hardly jump into the car. I was convinced that he wasn’t going to be with us for much longer and my heart ached for this beautiful, gentle animal that was trying so hard to maintain his dignified composure.

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