Like breast cancer in humans, tumors of the mammary glands are among the most common cancers in female dogs. However, most pet owners don’t see this type of cancer because it’s uncommon in animals that are spayed at a young age. Mammary cancer in dogs is fueled by estrogen, as it is in humans, so removing a dog’s ovaries reduces the risk.

But, among strays, and dogs used as breeders in puppy mills, one in four has tumors.

Mammary cancer in dogs respond to many of the chemotherapy drugs that are used in people, and have some of the same molecular abnormalities. And, as in humans, the risk of tumors increases with age, though some breeds, especially smaller dogs develop the cancer at higher rates than others.

They present a unique research opportunity, enabling scientists to study lesions that are at different stages of development – from benign to cancerous, and at transitional stages, all in the same animal.

“The dog gives us the potential to answer the question: When did something go wrong at the molecular level?” said Dr. Karin Sorenmo, chief of medical oncology at The University of Pennsylvania’s Vet’s Ryan Hospital. “We can also study the benign tumors and ask: What’s different in that one tumor that doesn’t change and become malignant versus another one that does change?”

This field of research is called comparative oncology, and is used to improve the understanding of the biology of cancer, and to fine-tune treatment of people. In the process, shelter dogs get access to treatment.

An example is Puddles, a fluffy 5 year old Maltese, who is part of a clinical trial at Penn Vet. She wears an “I am a survivor” tag which is permanently affixed to her collar. Other patients included Astrid, a Maltese mix, and Amy, an under-nourished Rottweiler.

A silver lining is that these stray dogs, who are getting free cancer treatment, are also helping the cause for breast cancer in women. More than 100 dogs have been through the program, and many of them have been adopted by women who have also survived breast cancer…….     4/1/14





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