Cancer risks

“Interestingly, cancers of the ovaries and uterus are rare in dogs. This could be because most dogs do not reach the age at which these cancers become more common. “…..”Purebred dogs are twice as likely to get breast cancer as are mixed breed dogs of the same age. The most important conclusion gained from examining studies of breast cancer in dogs is that early spaying protects against breast cancer.Review of the Epidemiology of Cancer in Dogs by Todd Bessinger

The greatest protection from spaying occurs if the dog is spayed before her first heat. The protective value of spaying drops steadily until age 2 1/2. If the bitch is spayed at or after age 2 1/2, the risk of getting breast cancer is statistically no different from a bitch which was never spayed. One study, however, found at least some protection from breast cancer when bitches were spayed up to five years of age. Clearly, however, the earlier a bitch is spayed, the less likely she is to get breast cancer… Unspayed bitches who were underweight as puppies have about half the risk of developing breast cancer as puppies who were of normal or above-normal weight. A related finding was that obese dogs with breast cancer were four times as likely to have more malignant, aggressive tumors than were dogs of normal weight. ….Dogs with undescended testicles (i.e., the testicles do not properly migrate to the scrotum but remain in the body cavity) have a markedly higher risk than other dogs to develop this type of cancer. Dogs with inguinal hernias are also at increased risk. Obviously, neutering of dogs prevents the development of this type of cancer….Osteosarcoma tends to affect larger breeds with a slight increase in incidence with age. Males are more likely to be affected than are females. And since neutered dogs and bitches have twice the risk of developing the disease as compared to intact dogs, hormonal factors are thought to play a role…Bladder cancers is dogs are more likely to occur in older dogs. Two studies found a one and one-half to threefold higher risk in females while a third study found no differences between the genders. This latter study did find that neutered dogs of both sexes seem to be at higher risk. “<