Cancer Dogs

Melanoma is a serious type of skin cancer that forms in melanocytes, the cells that give skin its color. According to the Skin Cancer Foundation, melanoma accounts for about three percent of all skin cancers. Roughly 68,720 new cases will be diagnosed this year. However, it can be very deadly, causing about 75 percent of deaths from skin cancer. About 8650 people in the U.S. will die from it in 2009.

A major risk factor for melanoma is excessive exposure to UV light. Research suggests one blistering sunburn during childhood can double the risk for melanoma later in life. Risk for melanoma is also higher among people with fair skin and light hair, atypical moles (called dysplastic nevi) or a family or personal history of melanoma.

Melanoma in Dogs

Many people consider cancer to be a human affliction, but the disease can affect dogs, as well. In fact, the American College of Veterinary Medicine reports cancer is the leading cause of disease-related death in older dogs, killing about half those over 10. Canine melanoma accounts for 7 percent of malignant tumors in dogs.

Unlike humans, canine melanoma of the skin tends to be benign. However, researchers estimate 56 percent of canine melanomas develop in the mouth area and most of these tumors are malignant. Some potential warning signs include: a dark, raised mass in the mouth, facial swelling, difficulty swallowing or eating, drooling, bad breath or odor from the oral cavity, mouth bleeding and/or tooth loss.

Since many pet owners don’t regularly examine a dog’s oral cavity, oral melanomas often go undetected until they have advanced. This cancer tends to be very aggressive and can quickly spread to other areas of the body, like the liver, lung or kidneys. Even after surgery to remove the original tumor, median survival time for dogs with advanced oral melanoma is less than 5 months.

Canine Melanoma Vaccine

One animal cancer treatment currently under study is the canine melanoma vaccine. The vaccine is produced using human tyrosinase, a protein on melanoma cells. Jennifer Baez, V.M.D., Veterinary Oncologist with the Center for Animal Referral and Emergency Services in Langhorne, PA, says, ideally, the non-canine version will train the dog’s immune system to recognize tyrosinase on melanoma cells as different from the protein on normal cells. If that happens, the dog’s immune system may mount an attack against the cancer.

The canine melanoma vaccine is intended for dogs with stage II or III oral melanoma that have been treated and achieved local control of the disease. The vaccine is administered through air-jet injection (no needles). Initially, four biweekly doses are given, followed by booster injections every six months.

According to manufacturer studies, a dog with stage III or IV oral melanoma receiving surgery and/or radiation therapy normally has a median survival time of less than 60 to 90 days. However, for dogs given the canine melanoma vaccine, the median survival time was extended to 389 days.

The Human Connection

Animal health experts say studying cancer (like melanoma) in animals may help scientists understand the nature of cancer in humans and come up with better ways to detect or treat human cancers. Baez says dogs make a great model for comparison because many tumors tend to have similar characteristics. In addition, since a dog has a much shorter life span, doctors can determine more quickly how the animal is responding or if a treatment is working.

Currently, the USDA has given conditional approval for the canine melanoma vaccine. Additional research is being done to ensure the safety and efficacy of the treatment. Baez says once the vaccine has been proved safe and effective for dogs, researchers may begin testing a similar version for humans.

For information on the canine melanoma vaccine, go to http://www.petcancervaccine.com.

For information on canine melanoma: American College of Veterinary Internal MedicineAmerican Veterinary Medical Association

For information on melanoma in humans: American Cancer SocietyNational Cancer InstituteThe Skin Cancer Foundation