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Dear Christopher Cat

My 7-year-old cat has a mammary mass. My veterinarian recommends spaying her and doing a mastectomy to remove the mass. How much more time will this give her?

Christopher Responds

I’m sorry to hear about your cat’s mass. In 90 percent of cases, feline mammary masses are aggressive, malignant tumors that rapidly spread to the lymph nodes, lungs and elsewhere in the body.

The most important factor in your cat’s prognosis is the size of her tumor when it is removed.

Cats with mammary masses less than 2 cm in diameter at the time of surgical excision live about three additional years. Cats with masses that are 2 to 3 cm (around 1 inch) when removed survive about two years. Sadly, median survival time for cats with masses over 3 cm in diameter is just four to six months.

If chest x-rays show the cancer has spread to the lungs, median survival time drops to less than two months, regardless of the mass’s size.

Mammary cancer develops, on average, at age 10 to 12. Siamese cats have a higher risk than other breeds.

The prevalence of mammary cancer is greatest in unspayed females. In fact, unsterilized female cats are seven times more likely to develop mammary tumors than spayed females.

Compared with unspayed females, the risk of mammary cancer is reduced 91 percent in cats spayed prior to six months of age, 86 percent in females spayed before one year -– and just 11 percent in cats spayed between one and two years of age.

Feline mammary cancer is most commonly treated with surgery, sometimes followed by chemotherapy. Radiation usually is not effective.

Our best wishes to you and your cat.



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