Melanoma is a cancer of the pigment-producing cells of the body. In humans, melanoma most commonly occurs on the skin, but in our canine friends, melanoma most frequently occurs in the mouth. These tumors can grow very large, impacting the dog’s ability to chew correctly, and very often the tumors invade the surrounding jaw bone, making them difficult to simply remove.
Oral melanomas are often not noticed until they are large because of their particular location. Think about the last time you had a good look around your dog’s mouth, including the inside and under her tongue. Most of the time, intimate evaluation of the mouth is reserved for veterinarians, who do their best during physical exams. Thorough examination of the oral cavity is always done during dental procedures under anesthesia, though, and is another great reason to pursue frequent dental cleanings.
Melanomas have a high rate of metastasis to the local lymph nodes and the lungs, and because they are often not detected until they are large, metastasis has often already occurred at the time of diagnosis. So, too, has the invasion of the surrounding bone. Melanomas are staged as follows:
- Stage I: <2cm in size
- Stage II: 2-4 cm in size
- Stage III: >4cm in size or tumors with spread to local lymph nodes
- Stage IV: any size tumor with distant spread
Average survival times are:
- Stage I: 1 year
- Stage II: 6 months with surgery
- Stage III: 3 months with surgery
- Stage IV: 1 month
Treatment begins with aggressive surgery. When the tumor has invaded the bones of the jaw, those must be removed as well. Furthermore, radiation therapy is generally recommended to kill the remaining cancer cells.
Recently, an additional weapon against canine oral melanomas has been developed: the canine melanoma vaccine.
The premise of this vaccine is the same as the other vaccines your dog gets. The vaccine’s job is to cause the dog to mount an immune response effective in killing the active form of the organism in the body. In the case of the melanoma vaccine, human DNA is used to induce antibodies against the melanoma cells. It is safe and potentially therapeutic, especially in stages II and III of the disease, where it is currently licensed for use when the tumor is locally controlled.
The melanoma vaccine is not meant to be used alone. As stated above, it is meant for cases that are already locally controlled, either through surgery or through surgery and radiation. The vaccine is used in combination with these treatment modalities to increase survival time. Even cases that had a guarded to poor prognosis can live a year or more with the use of the canine melanoma vaccine.
If your pet has been treated for an oral melanoma, please talk with your veterinarian about whether he can benefit from the use of the canine melanoma vaccine.