Oral Melanoma: Extended Survival Times

Filed Under: Dogs, Diseases

Oral melanoma—a tumor found in the mouth of your dog—tends to be aggressive. These types of tumors are frequently malignant, and will spread throughout the body often before they are diagnosed. Luckily, routine yearly physical examinations can yield an early diagnosis.

Melanomas may also be seen occurring in the nail bed area, footpad and mucous membranes. These tumors are often diagnosed on a scale of 1 to 4—the 4th stage being the most aggressive—depending on certain actors: the size of the tumor at the time of diagnosis, the histological characteristics and the presence of any detectable metastatic disease, usually seen in the local lymph nodes and lungs. Oral melanomas, regardless of their stage, should be considered potentially fatal.

Dog owners often have difficulty in detecting an oral problem. Many dogs resist examination of the mouth or dislike having their teeth brushed, unless this practice is started at an early age. However, dogs do tend to show a variety of clinical signs when they are affected by mouth tumors. These include bad breath, loss of teeth, difficulty chewing or swallowing, excessive salivation, a decrease in appetite and even possible facial swelling.

Melanoma is traditionally treated with surgery and/or radiation therapy. Response rates to chemotherapy have generally been poor. The median survival time for Stage 2 melanoma is 150 days; for Stage 3 and above, less than 90 days. Regardless of stage, surgery should first be conducted to remove the entire tumor whenever possible. Fortunately Merial has recently been given a USDA conditional license for a therapeutic DNA vaccine which has prolonged survival times to an average of 389 days.

The Canine Melanoma Vaccine by Merial is a xenogeneic tyrosinase vaccine. This means the vaccine is made from the DNA of another species—in this case, human tyrosinase that is inserted into a DNA plasmid. The tyrosinase is different enough from the canine tyrosinase protein that an immune response will be created. At the same time, it is similar enough to the canine tyrosinase than the immune response will be directed against the melanoma tumor cells. Through vaccination, both T-cell and antibody immune responses are stimulated. The course of treatment is an initial series of 4 biweekly vaccinations, with a booster dose recommended at 6 month intervals. Negative reactions to vaccination has been remarkably low. Some dogs have had a low-grade fever following vaccination. Since licensure at this time is conditional, access to vaccinations has been limited to cancer specialists. For a veterinary oncologist in your area, visit www.acvim.org or www.vetcancersociety.org.

Topics: cancer, oral conditions

Symptoms: bad breath, difficulty eating, hypersalivation, loss of appetite, swelling, tooth loss

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