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Possible Causes of Cancer in Dogs

Kelly Roper

Did you know cancer in dogs will likely affect 50 percent of our canine companions by the time they reach their senior years?

What Exactly Is Cancer?

The most simple explanation for cancer is that it is unchecked abnormal cell growth. Normally, body cells follow a regulated pattern of cell growth, division, and death. New cells replace old cells as they die off, and all is right with the world.

Abnormal, cancerous cells behave differently. They follow a pattern of continuous growth, far outliving normal cells as they conglomerate into growths known as tumors. While not every tumor is automatically cancerous, tumors diagnosed as malignant are cancerous and pose the biggest threat to a dog's health. Even non-cancerous tumors, known as benign, can cause problems if they grow large enough or wrap around major blood vessels and vital organs.

Eventually some of these cancerous cells will break away from the others and travel through the bloodstream to take root and grow in other parts of the body. This process is known as metastasizing and leads to widespread cancer in the animal.

What Is the Cause?

At its deepest root, cancer is caused by damage to the DNA. DNA is found in every cell and is responsible for directing cells in normal behavior patterns. Under normal circumstances, the body is able to repair DNA damage, but when that damage isn't repaired, the cells begin to behave abnormally, beginning the out-of-control growth that leads to cancer formation.

Alarming Statistics on Cancer in Dogs

The statistics on cancer in dogs is a bit alarming, and in fact, the current rate of cancer is higher in dogs than it is in humans.

According to recent stats from VPI Pet Insurance, dogs are:

  • Twice as likely to develop leukemia than humans
  • Four times more likely to suffer from breast cancer
  • Eight times more likely to develop bone cancer
  • An incredible thirty-five times more at risk for developing skin cancer

So the question begs, why is cancer in dogs so prevalent? The answer likely lies in the amount of exposure our pets receive to carcinogens in their environment.

Dogs may actually be consuming carcinogens in their dog food. Some of the chemicals used to preserve pet foods have been revealed to be cancer causing agents. Sadly, Mouth cancer is actually the fourth leading cause of cancer deaths in dogs.

Dogs regularly inhale unseen cancer causing materials. When does a dog ever really stop sniffing everything it comes in contact with? Carcinogens in the environment tend to settle on the ground and other objects, where they remain in trace form until Fido sniffs them up. These carcinogens may have a cumulative effect and eventually cause one or more types of cancer to develop.

Dogs get a lot of sun exposure. Of course, sunshine and fresh air are both good for dogs, but how many of us consider sun protection for our pets. Yes, responsible owners provide shade for their pets to escape the sun, but on mild days, a dog is just as likely to bask in the sunlight for hours. This can result in a phenomenal amount of ultraviolet exposure and is likely the culprit responsible for so many incidences of skin cancer in dogs.


Different types of cancer grow at different rates and respond better to certain types of treatment than others. While there as yet is no sure cure for cancer in dogs, the following treatment methods can be effective to a certain extent.

  • Radiation therapy
  • Chemotherapy
  • Standard surgical reduction/removal
  • Cryosurgery or freezing of the tumor tissue
  • Complimentary dietary and herbal therapies

Of course, the best chance for your pet to survive cancer lies in early detection. Regularly check your dog for unusual growths, take major changes in eating habits or behavior seriously, and contact your vet right away if you suspect a problem.

Possible Causes of Cancer in Dogs