The Dog Cancer Survival Guide (108 page)

When you need to look up the definition of a word or phrase, find it listed in
Chapter 5
, which begins on
page 46
.

Oral cancer, the fourth most common type of dog cancer, is typified by several types of tumors that can occur in the oral cavity. The most common is melanoma (discussed separately in
Chapter 40
) and the second most common are squamous cell carcinomas, or tumors that develop in squamous epithelial cells. The word squamous is Latin for “scale,” as in scales on a fish, and describes the way these often-flat cells tend to overlap. Epithelial cells generally line the inside of the body, so there are many squamous epithelial cells in the oral cavity. Squamous cell carcinoma is often referred to by its initials, SCC. These tumors are locally invasive, spreading into the surrounding tissues, and they often involve the bone by the time of diagnosis. Depending upon where SCC occurs, it may or may not spread distantly. SCC found deeper in the mouth (in the caudal region at the back), at the base of the tongue, or on or around the tonsils tends to be more metastatic.

A less common oral tumor, fibrosarcoma, accounts for 10-20% of cases. Sometimes called fibroblastic sarcoma, usually shortened to FSA, fibrosarcomas are tumors that develop in fibroblasts, specialized cells responsible for creating connective tissue. They are very invasive to local tissues, although less metastatic than SCC; metastasis occurs in less than 30% of all FSA cases. When it occurs, metastasis spreads to the lungs and occasionally regional lymph nodes in the head and neck.

Some tricky FSA tumors look benign under the biopsy microscope, then behave in the body like very aggressive malignancies. They grow extremely rapidly, recur often and invade the bone. These FSAs are given a mixed name to match their mixed appearance and behavior: Hi-Low FSA. They commonly occur on the upper jaw (maxilla) and the roof of the mouth (palate) of large breed dogs, especially the Golden Retriever. If your dog’s FSA is called benign but behaves like an aggressive malignancy, it is probably a Hi-Low FSA, and should be treated like a malignancy.

The remaining oral tumors, about 5%, are benign tumors, called dental tumors, including epulides and ameloblastomas. Most of these tumors are easily controlled with surgery or radiation, do not metastasize and have a great prognosis when treated as outlined here. Please note that while classified as benign, these tumors can still have malignant effects, and should be treated.

While tobacco use, especially combined with alcohol use, has been proven to cause oral cancer in humans, the cause of most canine oral cancer is not known, with one exception. Oral carcinomas and sarcomas can occur years after radiation therapy is used to shrink benign dental tumors.

There are some risk factors associated with oral cancers: male dogs tend to develop more oral cancer of all kinds than females do, and white dogs seem to be predisposed to SCC of the tongue. SCC of the tonsils is ten times more likely to occur in dogs that live in urban areas. Oral FSA and SCC are more common in large breed dogs. Oral FSA also occurs more frequently in male dogs.

Some breeds are more likely to develop oral tumors: Doberman Pinschers, Golden Retrievers, Gordon and Irish Setters, Schnauzers, Cocker Spaniels, German Shepherds and Scottish Terriers. Oral FSA occurs more frequently in Golden Retrievers and Labrador Retrievers. Acanthomatous ameloblastoma, a benign dental tumor, occurs more commonly in Shetland and Old English Sheepdogs.

Dogs are usually brought in to the vet for symptoms such as bad breath, excessive drooling, difficulty in eating or swallowing, pain while eating, pawing at the mouth, bleeding teeth, bloody saliva, tooth loss, facial swelling or ulceration and weight loss.

Most oral tumors are not noticed until they are advanced, because most owners do not look in their dogs’ mouths on a regular basis. Those who practice daily canine oral hygiene and make regular dental cleanings a priority tend to find oral tumors early, which is vital for an optimal outcome. The earlier a tumor is found, the smaller it is likely to be, and the less invasive to surrounding tissues.

Tumors located towards the front of the mouth (the rostral region) are usually noticed earlier, which means they are typically smaller at the time of diagnosis than those found in the back of the mouth (the caudal region).

Sometimes vets discover oral tumors during routine cleanings; loose teeth with little tartar or dental disease signal the possibility of cancer. In these cases, a tooth extraction and biopsy of the socket is in order.

Some dogs, especially if they are experiencing pain in the region of the mouth, need a short sedation for a thorough oral exam. The first test run is usually a fine needle aspirate, which can provide a preliminary diagnosis. (Dogs may not need sedation if their mass is rostral (towards the nose).) To get a more concrete picture of what type of tumor is present and what the prognosis is, a biopsy is recommended, and this is usually done during the oral exam, since the dog is already sedated.

Biopsies should be taken from inside the oral cavity (not from the outside of the body), to avoid contaminating normal tissues. Oral tumors are often infected or necrotic (filled with dying or dead tissue), so it is important to get a large enough sample to ensure that tumor tissue is included. The biopsy will determine whether the tumor is a melanoma, SCC, FSA or other dental tumor.

Most oral tumors are locally invasive into surrounding tissues, including bone; distant spread is less likely than with other cancers. Even so, I recommend more tests to discover how far the cancer has spread, because this knowledge can help you to understand your dog’s prognosis and plan treatments accordingly.

Depending upon the case, your vet may want to run blood work, a urinalysis, three-view chest imaging or a chest CT scan, abdominal ultrasounds and lymph node aspirates.

Lymph nodes are particularly important to aspirate, because you cannot tell by their appearance whether they are metastatic. For example, in one study, 40% of dogs had normalsized lymph nodes that had metastasized, while half of dogs with enlarged lymph nodes did not have metastasis. The bottom line is: lymph node size does not correlate to metastasis, so aspiration is indicated for both normalsized and enlarged regional lymph nodes.

The head and mouth have many complicated structures and many lymph nodes, so there are several to check. For example, lymph nodes on the right side of the jaw may drain the left side of the jaw, and vice versa, which means a mass on the right side may metastasize to the left lymph node; both sides should be checked, as should the long chains of lymph nodes deeper in the head and neck.

Highly detailed CT scans or dental radiographs (X-rays) are often needed to really understand just how invasive and extensive an oral tumor has become. This information will help determine treatment decisions later.

With the wide variety of tumor types, there is a wide variety of prognoses, plus some general prognostic factors to keep in mind.

The official staging system for canine oral tumors is as follows:

• Stage I:
  The tumor is smaller than 2 centimeter in diameter, with no metastasis to regional lymph nodes.
  
• Stage II:
  The tumor is 2-4 centimeter in diameter, with no metastasis to regional lymph nodes.
  
• Stage III:
  The tumor is over 4 centimeter in diameter, and/or there is metastasis in one or more regional lymph nodes.
  
• Stage IV:
  The tumor is any size, with distant metastasis.
  

The higher the stage is, the worse the prognosis. In general, tumors at the back of the oral cavity have a worse prognosis. Tumors that recur also worsen the dog’s prognosis.

Oral tumors tend to progress locally, and most dogs die as a result of this local disease. If left untreated, symptoms tend to get worse, and dogs progressively and sometimes rapidly lose their quality of life. Watching their dogs experience progressively worsening pain, difficulty while eating or swallowing, oral bleeding, tumor infections and weight loss typically prompts owners to choose euthanasia.

Both SCC and FSA tumors have often involved the bone and invaded other local tissues by the time they are diagnosed, so the goal of treatment is to control the region with surgery and/or radiation.

The first treatment is usually surgery. Complete excision is essential, as second and third tumor surgeries are usually unsuccessful and recurring tumors worsen your dog’s prognosis. An aggressive surgeon, who will make wide excisions, is more likely to achieve complete tumor removal, so I recommend a specialist who is comfortable and experienced in oral surgeries. It is worth the added expense to get this surgery right the first time.

The conventional treatments Dr. Ettinger recommends for oral cancer should be considered part of step one of Full Spectrum cancer care (
Chapter 11
). Please review that chapter for more general information about surgery, radiation and chemotherapy and how to handle their common side effects.

For more information on all other Full Spectrum steps, including nutraceuticals, immune boosters, dietary changes and brain chemistry modification strategies, review Full Spectrum cancer care, which begins on
page 103
.

You will also find information about specific chemotherapy agents in
Chapter 41
.

While it is hard to imagine your dog missing a large part of her jaw, I can report that owners are usually satisfied after the surgery. Radical surgeries are usually well tolerated by the dog, even when large portions of the jaw must be resected. They feel less pain, and they can still use their mouths well. Often surgeons can show you a picture of a dog with a similar procedure so you can visualize what your dog will look like after having healed from surgery.