Dogs Join the Fight Against Human Cancer.
About 5 years ago, when Breezy, a Rotweiller, was two years old, she got sick. In surgery we removed a tumor from her small intestine. The lab diagnosis was malignant cancer. It looked like she had at most a couple of months to live. But she has been fine until a few months ago when she came in three legged lame with a lump in her elbow. A biopsy indicated it was a similar type of malignant cancer. We referred her to the WSU Veterinary Teaching Hospital and now, after surgical removal of most of the tumor, and radiation therapy, she walks without a limp. Chemotherapy is planned to hopefully eradicate the cancer completely. For now, Breezy is again greeting us with both front feet on the counter and a big smile on her face.
Inexplicable things like Breezy's full recovery from intestinal cancer sometimes happen in human medicine as well. The December issue of Scientific American magazine and the November 24 issue of the New York Times each had articles about dogs and cancer. Dogs and many other animals have been used in laboratory experiments for years to study cancer and other human diseases. But there is now a growing trend to enroll pet dogs that have been diagnosed with cancer in human cancer research studies, including clinical trials using the newest drugs.
In studies using mice or other lab animals researchers would typically use drugs to suppress the immunity of the animals, then give them cancer by injecting them with massive doses of cancer cells, or compounds that were suspected to cause cancer. The trouble with this is the cancer is not only in an animal instead of a human, it is also an unnatural type of cancer created in an unnatural way. Results were often not applicable to cancer in humans. It is not practical to maintain a huge colony of laboratory mice or dogs for the years it would take until enough of them naturally get cancer. It would cost too much money and take too much time.
The Scientific American article estimates that of America's pet dogs, 4 million will be diagnosed with cancer this year. Researchers are now beginning to take advantage of this huge "colony" of pets, and many dogs unlucky enough to get cancer will reap some benefits of state of the art cancer prevention, diagnosis and therapy.
Cancer treatments that should theoretically be of benefit may be evaluated in pets suffering from cancer that has occurred "naturally." Effectiveness and side effects can be more accurately evaluated. Critical information can be gathered about doses and treatment schedules.
The 15-year lifespan of a typical dog as compared to 80 years or so in humans means the effects of environmental factors, such as exposure to asbestos and many other potentially toxic compounds will become apparent much more quickly in dogs. Strategies to prevent some kinds of cancer can be evaluated within a dozen years or so by gathering statistical data from owners of pet dogs, as opposed to fifty or sixty years in humans. Furthermore, reproduction begins much earlier in dogs than in humans. This makes it much easier to gather data through several generations about how resistance to cancer, and a tendency to get certain kinds of cancer, is transmitted genetically from parents to offspring.
Dr. Janean Fidel, cancer specialist at the WSU Veterinary Teaching Hospital, and the doctors at the Washington Animal Disease Diagnostic Laboratory have a special interest in Breezy. Her apparent susceptibility to cancer, but also an apparent ability to fight off the disease, may someday help unravel similar phenomena in humans.