ORAL SQUAMOUS CELL CARCINOMA (FELINE)
The squamous cell carcinoma is not only the most common oral malignancy of the cat, it carries one of the poorest outcomes. In most cases, the goal ends up to be minimizing infection and pain until the tumor has advanced to a state where comfortable eating and/or breathing is not possible. The tumor is treatable only if detected very early in its course.
PREVENTION AND RISK FACTORS
While sun exposure is an important risk factor for squamous cell carcinoma on the ears and nose, the owner’s cigarette smoking habits turn out to be one of the most important risk factors for the oral squamous cell carcinoma. The risk goes up four times when the owner smokes 1-19 cigarettes daily. Cats that have at one time lived with a smoker have an increased risk over cats that have always lived in non-smoking homes.
In one study, the use of flea collars was associated with a five-fold increase in the development of oral squamous cell carcinoma though the study that found this correlation was not able to differentiate between different types of flea collars (there are many) so it is difficult to interpret this data. Interestingly, regular flea shampoo use was associated with a 90% reduction in risk (perhaps a surface toxin is washed away by frequent bathing).
Regular feeding of canned food, especially tuna fish, was associated with increased risk for the development of oral squamous cell carcinoma. In humans, poor oral hygiene has been associated with an increased risk for oral squamous cell carcinoma so it has been speculated that this is the basis of the canned food correlation in cats as well.
The average age at diagnosis is 12.5 years. This is usually a tumor of older cats.
GET COMFORTABLE LOOKING IN YOUR CAT’S MOUTH.
WHERE TO LOOK
The squamous cell carcinoma often grows from the gums surrounding the teeth or under the tongue. To look under a cat’s tongue, press your thumb upward from under the chin (in the soft area between the lower jaw bones). This will raise the base of the tongue upward; when the cat’s mouth is open, it’s easy to see the root of the tongue. Become familiar with the symmetry and contour of your cat’s jaws, both upper and lower.
WHEN IT COMES TO ORAL SQUAMOUS CELL CARCINOMA,
REGULAR TEETH CLEANING IS IMPORTANT FOR ALL PETS.
Benign lesions can look similar to malignant lesions to the naked eye, and possibly even on radiographs, so a biopsy needed is for the correct diagnosis. In most cases, some kind of sedation and dental evaluation is needed to get close enough to the area in question. If a small sample of tissue can be harvested, the diagnosis should be revealed.
Sometimes suspicious tissues are aspirated with needles to harvest cells for diagnostic purposes. It is particularly helpful to aspirate an enlarged lymph node or swelling to test for the presence of tumor. Aspiration is not as accurate as biopsy but is less invasive and may not require anesthesia depending on the location of the suspected tumor. Fine needle aspiration is a test your veterinarian may recommend.
Radiograph of a cat’s lower jaw showing bone destruction typical of a squamous cell carcinoma
The squamous cell carcinoma is a very destructive tumor. Underlying bone is commonly eaten away. Findings of bone destruction on a radiograph may also be helpful in establishing diagnosis.
Computed Tomography (CT or “CAT scanning”) is needed to determine the extent of the tumor. If surgery is being considered, knowing the tumor margins is crucial and radiographs simply cannot accurately show how far the tumor extends. Referral to a specialty hospital or imaging center is frequently needed for this type of testing.
Sadly, options are limited for the treatment of the oral squamous cell carcinoma; fewer than 10% of cats survive one year from the time of diagnosis. Cats are euthanized when they become too disfigured to eat or breathe. Still, the situation is not without options and some situations are more favorable than others.
If the tumor is located on the lower jaw, it may be possible to remove the part of the lower jaw that contains the tumor. This surgery is called “mandibulectomy,” and is preceded by a CT scan (where available) to determine the margins of the tumor.
If the tumor is located in the upper jaw, surgery is probably not an option (see below).
Mandibulectomy Combined with Radiotherapy
The longest survival times have been yielded by a combination of surgery and radiotherapy (14 months). The study reporting this rather long survival time only reviewed seven affected cats, a relatively small number upon which to draw generalizations. These cats, however, all required feeding tubes for a median of 15 days and had drooling issues and required regular cleaning (usually daily) on the chest and feet long term.
Radiotherapy with or without Chemotherapy
Radiotherapy can be definitive (intended to cure) or palliative (intended to slow disease and improve life quality but not cure). If surgery can reduce the tumor size to what is called "microscopic disease" (meaning no tumor is visible to the naked eye), radiation after healing provides the longest survival times. If the tumor is too large to remove to this state, definitive radiation is not going to be possible but palliative radiation is still an option if it is aggressively done (twice daily treatments for 9-10 days). In this situation, median survivals of 5-6 months were obtained. Similarly, another study showed promising results: a group of 11 cats with oral squamous cell carcinoma treated with a combination of radiation and the chemotherapy agent mitoxantrone yielded complete remission in 8 cats with a median duration of 170 days. It should be noted radiotherapy is generally a very expensive treatment and, when the mouth is involved, can create enough inflammation that a feeding tube is necessary to support the patient.
CHEMOTHERAPY ALONE HAS SHOWN SUCH POOR EFFICACY
Non-Steroidal Anti-Inflammatory Drugs
It has recently been found that certain tumors, particularly carcinomas, have receptors to bind the enzyme “cyclooxygenase” (lovingly known as “COX”). This enzyme is involved in the production of biochemicals (called “prostaglandins”) which are involved in the generation of inflammation. Cyclooxygenase inhibitors such as piroxicam and even meloxicam, two drugs more commonly used against arthritis pain, may have anti-cancer properties beyond simply controlling inflammation and pain associated with tumors. Often these drugs are prescribed for cats with oral squamous cell carcinoma but it is important to be aware that cats can be sensitive to their side effects. Often treatment of the tumor justifies this risk but, still, one should be aware of potential complications and should discuss the timing of monitoring blood tests with their veterinarian.
The bottom line is that the oral squamous cell carcinoma is a very bad tumor for a cat and as yet research has not yielded a reliably good therapy. Because the tumor does not spread until late in its course, removing the tumor when it is small is the only hope for a worthwhile survival time. The lower jaw tumors are best suited to this kind of therapy; other forms, such as tumors under the tongue or in the upper jaw, are nearly impossible to address meaningfully. It is important to keep a realistic attitude about what to expect.
Information in this article was largely obtained from the following review article:
SQUAMOUS CELL CARCINOMA OF THE UPPER JAW
As mentioned, it is very difficult to achieve meaningful treatment for a squamous cell carcinoma in the upper jaw and less than 10% of patients are still alive one year after diagnosis. In fact, most cats have stopped eating and require euthanasia within one month or so. Even with palliative radiotherapy only 1-4 months of survival are reported. That said, a new therapy is emerging in the form of aggressive radiotherapy. This protocol involves twice daily radiation of the tumor area for 7 days. With this protocol 56% of feline patients had no discernable tumor after therapy for an average of 13 months. A feeding tube is placed during the time of therapy and through the recovery time afterwards until the cat is eating well and the site of radiation is healed. This kind of therapy is relatively expensive but for a 50:50 shot at a long remission it may well be worthwhile.
Page posted: 9/3/2007