Dogs, Cats Not Immune to Breast Cancer

Owners can take steps to protect their pets' lives from deadly disease.

Oct. 24, 2007 — -- With all the grooming, feeding and playtime considerations that come part and parcel with caring for a dog or cat, breast cancer concerns may be far from the minds of their owners.

However, as with humans, beloved household pets can also develop cancer in the breast tissue — known in animals as mammary cancer. In fact, cancer is the No. 1 natural cause of death in older pets.

But with a little know-how, animal owners can help catch tumors before they become deadly.

"It's a fairly common cancer, especially in unspayed female dogs and cats," said Gerald Post, a veterinary oncologist at the Veterinary Oncology and Hematology Center in Norwalk, Conn. "It's important for owners to spay female animals before the animal first goes into heat, because each following heat cycle increases the risk of developing the cancer."

Pets with mammary cancer follow basically a similar type of treatment and recovery as humans with breast cancer. However, pet tumors are often not discovered until later, when the cancer has reached a more advanced stage.

About half the mammary tumors that dogs develop are noncancerous, which is similar to the ratio of nonmalignant tumors women find in their breasts. In cats, however, 90 percent of mammary tumors are cancerous. Vets say that these types of tumors closely follow the model of more aggressive forms of human breast cancer.

Advanced Warning for Owners?

And cancer in a pet, in some cases, may provide owners with an "early warning system" of sorts.

"The age-adjusted rate of cancer is actually higher in dogs and cats than in people," said Greg Ogilvie, director of the California Veterinary Specialist's Angel Care Cancer Center. "Pets have genetic factors, but they also live in a more polluted environment, and they have passive smoke exposure."

Part of the problem may be the toxins that find their way into the air, water, and human households, where pets also live. Because humans and animals share the same environment, some animal cancer experts say that our pets may provide a good indicator of the risks of cancer around us.

"We should really be monitoring pets with tumors closely," Post said. "Environmental problems are the same for animals and people. We can find cancer in our pets sooner [due to their shorter life spans], so we may be able to use them as models. Animals may be like the canary in the coal mine, telling us risk factors that we should be aware of."

Protecting Your Pet

The most important message from vets is to spay female animals before they go into heat. In addition to this, however, there are other ways you can help your pet.

"Leading a healthy life with healthy food can help," said Nicholas Dodman, director of the animal behavior program at Tufts University.

Pet owners should also take their animals to a veterinarian for an annual physical exam, but in the meantime, they can also check their pets manually.

"You can palpate the mammary glands — give them a good feel once a week or once a month," said Post.

Careful inspection, with both eyes and hands, of an animal's mammary glands can mean earlier detection and more successful treatment of mammary cancer.

"If any firm mass or red areas are present, then the pet should be evaluated by a veterinarian," said David Hunley, a veterinary oncologist with the Ocean State Veterinary Specialists in Greenwich, R.I. "The average age that these tumors are found is about 10 years in both the dog and cat."

According to the American Veterinary Medical Association, the most common signs of cancer in small animals include abnormal swellings that persist or continue to grow, sores that do not heal, weight loss, loss of appetite and bleeding or discharge from any body opening.

Pets with cancer may also give off an offensive odor, have difficulty eating or swallowing, show a hesitation to exercise or a loss of stamina, display persistent lameness or stiffness and have difficulty breathing, urinating or defecating. An owner should take an animal to a clinic if they notice any of these signs.

"Early detection and diagnosis is the key to great health," Ogilvie said, adding that if the cancer is detected early, animals have a good rate of survival. Then, they can continue to help amuse, annoy and comfort their human companions for many more years to come.