Oral Malignant Melanoma in Dogs and Its Vaccine: Page 2 of 2

Diagnosis

Expect your vet to examine your pet, taking care to examine its mouth and feel for enlarged lymph nodes. Your vet will likely want to biopsy any noted mass and take X-rays to see if the suspected cancer has spread to lymph nodes and/or lungs. Oral melanoma is known for spreading, called metastasis, to places in the body both close and far (14-74%) from the original tumor. Other than the lymph nodes, CMM is most known to spread to the lungs.

 

Treatment

Oral melanoma can be treated, but survival time is greatly based on the size of the original tumor, how early it was found, and the success of the first round of treatment.

The most common treatments for oral melanoma are surgery and radiation therapy. As this is a very important decision to make as an advocate for your pet, it is important to understand the projected survival time of your pet. This may help you determine what extent of treatment you wish to seek for your beloved pet.

As with all cancers, the sooner oral melanoma is diagnosed and treated, the better the outcome. Unfortunately, any melanoma is considered to have significant metastatic potential (potential to spread to other organs), although this risk increases with tumor diameters greater than 2cm.

Reported (not median) survival times after surgical removal of the tumor range from three to 45 months. Dogs with a primary tumor less than 2cm in diameter have reported survival times from 14.9 to 20 months and five to six months for larger tumors. Melanomas are also responsive to coarse‐fractionated external beam radiation therapy, although the addition of radiation therapy to surgery will not predictably increase survival time. As distant disease (melanoma spread to other organ systems) is the most common cause of death in these cases, pre‐treatment staging to determine if the cancer has spread to other parts of the body is imperative.

Luckily, though, there is a vaccine for oral melanoma. Unlike regular vaccines, the melanoma vaccine is indicated for the treatment of dogs with stage II or stage III oral melanoma on which surgery has already been performed to remove the primary tumor. This means that the vaccine is used more as a treatment than as a preventative measure.

If your dog is diagnosed with oral melanoma, be sure to ask your vet about the vaccine and what it could mean for your pet’s prognosis. Historical median survival times for dogs with advanced stages of oral melanoma that are treated with conventional therapies (surgery and radiation therapy) are one to eight months. In initial trials, this type of novel vaccine has resulted in significantly extended survival times for dogs with melanoma - 389 days is the median length. The vaccine works by alerting the immune system to the presence of the human melanoma tumor protein tyrosinase, which is similar enough to canine tyrosinase to induce a response against melanoma cells. Currently, the canine melanoma vaccine is only available to board-certified veterinary oncologists.