The Dog Cancer Survival Guide (119 page)

In the case of an oral tumor, both the left and right mandibular (lower jaw) lymph nodes should be aspirated, because lymphatic draining can cross to the opposite side of the jaw. In other words, a mass on the right side of the mouth can metastasize to the left lymph nodes. There are also chains of lymph nodes in the head and the neck that should be checked. These cannot typically be felt on an exam, but they can be detected on a CT scan.

I strongly recommend a CT scan for oral melanoma. The amount of detail you can see in a CT scan (or in dental X-rays, if need be) is extremely helpful in planning treatments. The tumor may be much more invasive and extensive than it seems on examination, and this information can inform treatment decisions later.

Melanoma behaves differently, depending upon the location (more specifics are discussed in the treatment section); the most malignant form is oral malignant melanoma.

This is the official clinical staging system for canine oral malignant melanoma:

• Stage I:
  The primary tumor is smaller than 2 centimeter in diameter, with no lymph node involvement.
  
• Stage II:
  The primary tumor is between 2 and 4 centimeter in diameter, with no lymph node involvement.
  
• Stage III:
  The primary tumor is larger than 4 centimeter in diameter, with or without lymph node involvement.
  
• Stage IV:
  The primary tumor is of any size, with distant metastatic disease.
  

Dogs with oral melanoma who do not receive treatment have a median survival time of about two months. In general, the prognosis is better for dogs with a tumor under 2 centimeters in diameter, with no lymph node metastasis, no bony invasion, and a low mitotic index, as revealed under the microscope (a low mitotic index is anything less than 3/10 highpowered field).

The first course of action with any melanoma is surgery to remove the primary tumor. Radiation may be necessary to control local microscopic disease, and the melanoma vaccine (or chemotherapy) is recommended to control distant metastasis. Let’s look at each of these melanoma types separately, to get a more detailed picture.

If there is no evidence of metastasis in distant body locations, and if wide (wider than two centimeters) margins, including underlying bone, can be obtained, surgery is recommended for oral melanomas. Lymph nodes that drain the region of the tumor that test positive should also be removed surgically.

These surgeries are easier if the tumor is small, forward (rostral), and involve the lower jaw (mandible). Surgeries on the mandible also tend to have lower recurrence rates. Sometimes the surgery must be quite radical, even removing half of the lower or upper jaw. Even so, owners report high satisfaction with these aggressive surgeries because they feel the mouth is less painful and still retains functionality. The median survival time for these resections is eight to ten months.

Of all the prognostic factors, the two most predictive factors in formulating a prognosis for your dog are the size of the primary tumor and the ability of the first treatment (usually surgery) to control the disease. When the tumor is smaller than two centimeters in diameter with no metastasis, and is treated with aggressive surgery resulting in clean, wide margins, the median survival time is seventeen months. Boarded surgeons tend to be more aggressive in their surgeries, which is why I recommend using one, if you can.

When the primary tumor is greater than two centimeters in diameter, or there is already lymph node metastasis, the median survival time with aggressive surgery is much shorter: four months. Dogs that get a conservative surgery (margins less than two centimeters wide and/or with dirty margins) have a 70% chance of recurrence and survival times of three to four months. These statistics explain the importance of early detection and an aggressive surgery.

Radiation therapy can be used as an alternative to surgery when the tumor is inoperable or you do not want to use surgery. In these cases, over 80% of dogs can achieve long-term local control over the disease, with complete response rates of 50-70% (which means the tumor disappears for a time) and median survival times of five to nine months.

The conventional treatments Dr. Ettinger recommends for melanoma 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
.

There are fewer early side effects with melanoma radiation protocols, because they are not the same as traditional protocols. Called coarse-fractionation protocols, they feature fewer total treatments and higher doses per treatment. Higher doses at each treatment are required because melanoma cells are unique in their ability to repair radiation-induced damage. While there is an advantage to these protocols – fewer treatments, less anesthesia, fewer early side effects, less expense – there is a trade-off, too: your dog is more likely to have late side effects like bone damage, muscle damage and central nervous system damage, for example. I recommend close consultation with a radiation oncologist to determine whether the standard melanoma protocols are appropriate for your dog. If there is a good overall prognosis and an expectation of a longer survival time, she might recommend your dog receive standard doses over more sessions to minimize the late-occurring side effects.

Just as tumor size is predictive for surgery outcome, it’s predictive for radiation therapy outcome. Dogs with tumors smaller than two centimeters often have a survival time of fifteen to twenty months, whereas, dogs with larger tumors and more advanced disease, metastasized to distant locations, typically live only five to six months.

Dogs with oral melanoma typically die because of their distant metastasis, which is more likely to occur in dogs with larger tumors or dogs that have already metastasized at the time of diagnosis. Because of melanoma’s high rate of metastasis in general, following up surgery or radiation with systemic therapy (melanoma vaccine or chemotherapy) is an important part of the treatment plan for dogs with any stage of oral melanoma.

Carboplatin is the standard chemotherapy drug used for oral (and digit) melanoma, and it extends survival time to approximately one year after surgery. Its use, however, has dropped since the approval of the melanoma vaccine (see below), which is more effective. (Some oncologists use both.)

Fewer than 30% of dogs respond to chemotherapy when used as a standalone therapy in place of surgery or radiation, so it is not generally used on its own.

“We humans, when we hear cancer, we automatically think - imminent death and that is not always the case. Don’t panic. Make sure you seek as much information as possible about the cancer and treatment options because depending on the type of cancer there could be many treatment plans available. Do not rely on one medical opinion; I work with an oncologist and a holistic vet and they have been instrumental in helping my dog have the best possible immune system and therefore fight the cancer. Also, I am part of a few cancer groups. These groups can provide vital information for your pet because they have been there and done it. They also help you realize that there a lot of other people/dogs out there going through the same thing and can provide support.”

- Marian Beeman, Fairfax Station, Virginia