Robyn Elmslie, DVM DACVIM (Oncology)
Pet owners often ask me if there is any way that their pet’s cancer could have been diagnosed earlier and if early detection would have improved their pet’s treatment options and outcome. For some tumors, early detection is very difficult and might not improve treatment outcomes. However, in the case of oral tumors (i.e. tumors of the mouth) early detection is critical for a good outcome. Puppies can be taught to allow regular and thorough examination of their mouth, so that when they are older and their risk for cancer starts to rise, regular oral exams can become an important part of routine cancer screening at home. Routine oral exams are not possible in some dogs or in most cats and therefore should not be performed if there is risk of injury to the pet owner.
When oral examination is possible, the exam should include the lips, gums and teeth, upper and underneath surfaces of the tongue, and the hard and soft palate, and the back of the throat. When a pet owner is familiar with the normal appearance of their pet’s mouth, they are more likely to recognize a change that warrants evaluation by their family veterinarian. Routine, annual or biannual dental cleaning in the middle aged to older pet gives the family veterinarian an opportunity to evaluate areas of the mouth that the pet owner cannot examine when their pet is awake, thus providing a more thorough evaluation of the oral cavity. These steps will not guarantee identification of all oral tumors but will allow for early detection of most oral tumors.
Melanoma is a very aggressive oral tumor that occurs most commonly in dogs over 10 years of age and is found primarily in dogs with large amounts of pigmentation along their gum line or tongue. Commonly affected breeds include Chow-chows, black poodles, black Labrador retrievers, and Scottish terriers, but no breed is spared. When this tumor is detected early (ie pea sized) the survival times with surgery alone exceed 1.5 years, whereas when the tumor is larger (ie walnut sized) at the time of detection, the tumor has often already spread to lymph nodes and the average survival time with surgery alone drops to just 3 months.
Other common tumors in the mouth of dogs include squamous cell carcinoma, fibrosarcoma and acanthomatous ameloblastoma. When identified early, these tumors are often cured with appropriate surgical removal. While the rate of metastasis is low for these tumors, when they are very large surgical cure can be challenging to achieve, and may result in disfigurement. When complete surgical removal is not possible, these tumors will recur unless treated with radiation therapy. The time to regrowth of oral tumors after radiation therapy is inversely related to the size of the tumor at the time of treatment.
Early detection and treatment of oral tumors results in a better quality of life for the patient. When the pet owner can take an active role in evaluating their pet’s mouth, early cancer detection is possible.