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Canine Mammary Cancer

October is breast cancer awareness month. Did you know that more than a quarter of all intact female dogs will develop mammary tumors? That’s more than twice the rate in humans. In fact, per the Veterinary Society of Surgical Oncology, 42% of all diagnosed tumors in female dogs are mammary tumors.

Mammary cancer is an incurable disease with survival rates as low as a few months to a couple of years depending on the severity. Once a lump is noted in a mammary gland, it is best to seek diagnostics right away. The vet will likely want to do bloodwork, ultrasound, radiographs (x-rays), and a biopsy. All of these things are necessary to determine the prognosis. Even after tumor removal, which could be anywhere from one mammary gland to an entire chain of mammary glands, most patients still require chemotherapy as at least 50% of malignant mammary cancers have already metastasized (spread) by the time they are even noticed/diagnosed.

Chemotherapy does not affect dogs quite the same way as people. They won’t lose their hair and are not typically sick from chemotherapy. If anything, a small percentage of animals seem a little less energetic and vomit occasionally (less than 10% of patients). For mammary cancer, chemotherapy is usually administered every three weeks for 4-6 treatments.

Though mammary cancer is highly prevalent in intact female dogs, it is quite easily prevented by spaying a pet young. The American College of Veterinary Surgeons reports that a dog spayed before its first heat cycle has only a 0.5% chance of getting mammary cancer later in life. After their first heat cycle, an 8% chance. It is after the second heat cycle that their chances increase to over 25%, which is one of the main reasons veterinary professionals recommend spaying your pup while it’s young.

So spread the word that the most common cancer in female dogs can be prevented by early spaying. Support groups that offer low-cost or free spay and neuter clinics to help battle this disease. And adopt, don’t shop.

Article by Wendi Black




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