Canine Oral Melanoma
Routine Dental Care Can Help Detect Common Cancer
Christine Gowen, Pet HealthZone Editor
Dog owners may not know that their pets’ mouths may be harboring one very common, life-threatening disease: oral melanoma.
Routine dental cleanings not only maintain a dog’s pearly whites—they also provide a veterinarian the opportunity to conduct a thorough examination of the mouth for unusual pigmentation and hard-to-spot tumors that can be indicative of oral cancer including oral melanoma.
Catching melanoma in its earliest stage is your pet’s best bet for survival.
Oral Cancer Symptoms
Symptoms of oral cancer are similar to dental disease. Symptoms include:
- Bad breath
- Bleeding from the mouth
- Facial swelling
- A change of food preference (from hard kibble to soft food)
- A noticeable difference in chewing habits
- A decrease in eating
- Chronic coughing
- Difficulty swallowing
- Weight loss
Diagnosing Oral Melanoma
Oral melanomas commonly occur in older dogs with darkly pigmented areas of the mouth, tongue and gums. Cats also develop oral melanoma but other types of oral tumors are more common in the mouth of cats.
"During an examination, we’ll open the dog’s mouth and look for broken teeth, swollen gums or anything unusual," says Dr. Eric Van Nice, who specializes in advanced veterinary dental care at Animal Dental Services in Tustin, Calif. "We like to take a good look around, just like a regular dentist."
Oral melanoma and other oral cancers can present as a pigmented or non-pigmented fleshy masses anywhere in the mouth.
To conclusively determine that an oral tumor or cancer is present, your veterinarian will first examine your dog’s mouth, and then perform a biopsy of the affected tissue. The biopsy will determine if the growth or tumor is benign, pre-cancerous or cancer.
"It’s important to get a biopsy to find out exactly what it is," explains Van Nice. "The biopsy is then sent to a pathologist, who will define the type of cancer for us. Next, an oncologist will determine what stage of cancer—if any—exists. How far has the cancer gone?"
A chest X-ray, blood work and X-rays and/or CT scan of your dog’s jaw will help determine if the cancer has invaded the jaw bone or metastasized (spread) to the lungs.
Unfortunately, the average lifespan of a dog following diagnosis of the most aggressive stage of malignant melanoma is five to eight months.
Treating Oral Melanoma
The good news: oral melanoma can be treated. The bad news: complete removal of the cancer is difficult and many times part of the dog’s jaw has to be removed. Tumor recurrence and metastasis is common with malignant oral tumors.
"One of the first questions pet owners should ask is, 'How advanced is it? What is the stage of cancer?'" recommends Dr. Mona Rosenberg. Her nine-doctor oncology practice has grown into one of the largest and most technologically sophisticated veterinary oncology practice in the world since she opened the doors in 1992. As chief of staff of the Veterinary Cancer Group she exclusively treats pets diagnosed with cancer.
"We try to determine if cancer is still local to the area or if there’s evidence the cancer has spread," says Rosenberg. "Potential behavioral changes can indicate that the cancer has spread to the brain, although that's not as common as metastasis in the lymph nodes and lungs."
To aggressively treat melanoma, an oncologist will surgically remove as much of the tumor as possible, as well as any cancerous bone growth. Radiation will then target the affected area in order to reduce the chances of recurrence. Because the chance of cancer recurrence and rapid metastasis is so high, chemotherapy and/or immunotherapy will be suggested.
Unfortunately, the average lifespan of a dog following malignant melanoma diagnosis is five to eight months. On average, 30 to 40 percent of malignant tumors metastasize in the early stages and quickly spread to the lungs, lymph nodes and other organs.
"Radiation has been found to help kill off remaining cancer with minimum short-term side effects, similar to a cold sore that can heal within a week or two," Rosenberg explains. "Dogs with metastasis will benefit more from chemotherapy than vaccine therapy."
Oral Melanoma Vaccine
Keep in mind, that while a new DNA-based vaccine for oral melanoma is showing promise in the effort to improve a dog’s survival rate, it is not going to protect your pet from developing oral cancer.
"The vaccine—or immunotherapy—supports a pet's immune system but doesn’t prevent the disease from occurring," says Rosenberg.
In March 2007, Canine Melanoma Vaccine DNA, an anti-cancer vaccine created for dogs diagnosed with the disease, was conditionally approved by the U.S. Department of Agriculture. During the initial vaccine melanoma study, many dogs survived on average 389 days—an improvement from the usual five to eight months.
Today, while the melanoma vaccine is not a replacement for surgical, chemotherapeutic or radiation treatment, the potential to extend dogs’ lives has been encouraging when used in addition with another treatment, such as radiation. Dog owners interested in learning more about the vaccine should consult with their veterinarians; at this time, the conditionally licensed vaccine is available only to specialists practicing veterinary oncology and is recommended for dogs with stage II or stage III oral melanoma. Other stages are being treated as well; results are being measured to determine if the use of the therapeutic vaccine should be extended.
Make Wise Choices
"We try to give pet owners choices so they can consider the pet’s quality of life," Rosenberg says. "If the treatment is worse than the disease—that's something to consider, particularly with geriatric pets whose immune systems may be topsy-turvy.
"If the disease is localized we can get it with surgery relatively easily. Often times, melanoma is very invasive and it may require removing a portion of the jaw. We don’t want to perform deforming surgery if it's not going to offer a more long-term outcome. Radiation therapy may be a better option than removing a portion of the dog’s jawbone. A pet’s survival rate will depend on the stage of the disease."
Rosenberg recommends that pet owners watch for any signs pointing to oral problems, such as blood on chew toys or blood in a pet's water bowl. "We need to get the word out sooner [about oral cancer] so that pet owners are more aware of the symptoms and treatment options."
While there is no preventive care for malignant melanoma, routine dental checkups and a thorough oral examination can greatly aid in early detection and diagnosis of oral cancers, and perhaps save your pet’s life.
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A Note from the Pet HealthZone Editor:
Two years after initially writing this article one of my own dogs (the one pictured with me to the left), a very healthy 11-year-old Labrador retriever who had routine dental exams, was diagnosed with oral melanoma. I noticed her breath was particularly smelly and her drool was sometimes stained dark brown. What irony that she would then become a patient at Dr. Rosenberg's Veterinary Cancer Group, during which time she received treatment to target the tumor in the far recess of her mouth as well as the tumor that had grown in her first lymph node. Oral melanoma is typically very fast moving; we were warned our dog may only survive six to nine months following treatment.
The good news? The treatment worked: my dog has thus far survived oral melanoma two years after her diagnosis. She beat the odds. Going in her favor was her annual dental exam. Although the cancer spread to one lymph node, we caught it early on and the treatment stopped the growth, forced it into remission and preserved my dog's quality of life (she's now 13 1/2 and aging but still enjoying life). If you notice a change in your dog's mouth, such as bad breath or stained drool, don't wait: see your veterinarian immediately. Catch it before it's too late.
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