CANCER RISKS IN DOGS

- Spaying or neutering can reduce the risk of cancer. Dogs spayed before the first heat cycle have only half the risk of mammary carcinoma of those spayed after the first but before the second heat cycle. Dogs spayed after the fifth heat cycle or never spayed have the highest risk of mammary cancer. Testicular carcinomas or tumors in dogs are common, but having the dog neutered eliminates that risk. Testicular cancer rarely spreads in dogs, unlike in humans, so treatment has a high success rate.

- Dogs have a much higher incidence of nasal sinus cancer than do people. It is thought to be because they have more nose to get cancer in and because their noses are always to the ground sniffing up chemicals and other carcinogens that concentrate there. Carcinogens range from herbicides and pesticides for dogs in rural areas and factory or automobile pollution for urban dogs.

- The mouth is the fourth most common site of cancer in domestic animals. This is due to the carcinomas from the air that land on their coats and get into their oral tissues when they groom themselves. Swelling around a tooth when there is no tooth injury of dental disease could be a sign of mouth cancer.

- Older giant or large-breed dogs are predisposed to bone cancers at the ends of long bones. These may result from tiny stress fractures that occur during the rambunctious puppy stage. It is important to refrain from strenuous exercise and allowing the puppies to run for long periods of time (such as hiking trips) until the dog has stopped growing.  

- In any pet, the site of an injury or other trauma may later develop cancer. It is known for example, that cats sometimes develop sarcomas at vaccination sites. A dog may also develop sarcoma at sites of old bone fractures, especially those associated with chronic non-healing or with loose implants such as a metal plate or pin. Chronic inflammation is also associated with cancer.

To catch the disease in the early stages, pet owners need to be alert to change in their pet's behavior. Watch for rapid loss of weight; change in elimination habits; decreased energy level; physical symptoms such as sneezing or coughing, changes in the shape, texture, or size of a wart or mole or lump, or changes in behavior patterns. Be observant as dogs often hide symptoms. Dogs may (especially Dobermans) continue to do  things they don't feel well enough to do because they want to please their owner and because they are very stoic.

Submitted by Bonnie Dunlop with permission from Theresa A. Fuess, Ph.D. Information Specialist University of Illinois College of Veterinary Medicine