The American Veterinary Medical Association encourages pet owners to surgically sterilize their cats as early as possible, between 8 and 16 weeks of age. In the past, veterinarians would wait until cats had gone through their first heat or had a litter, but this practice increases the risk of cancer.
Cats that are surgically sterilized as kittens have a lower risk of mammary cancer than those that have or had intact sexual organs after puberty. This is likely due to the influence of sexual hormones. Mammary cancer in cats is often treated by removing the sex glands or putting the cat on antihormonal drugs. This is effective in treating the most common kind of tumors: those that contain sex hormone receptors. Although mammary tumors are more of a concern for cats with ovaries, cats in general benefit from having the surgery performed when very young, as the procedure has a lower risk of complications when the cat is a few weeks versus a few months old or older.