The Dog Cancer Survival Guide (117 page)

Perianal adenocarcinomas tend to recur, especially if they are larger than 5 centimeter in diameter at the time of diagnosis. For these tumors, a more aggressive surgery is required, with wide margins, and later surgeries may be necessary, if regrowth occurs. In these cases, the size of the tumor can predict the expected outcome: dogs with perianal ACA smaller than 5 centimeter live for two years, while those with perianal ACA over 5 centimeter live for one year. Dogs with metastasis at the time of diagnosis have median survival times of seven months, regardless of the size of the primary tumor.

Anal sac adenocarcinoma (ASAC) is even more aggressive, and may require a multi-modal approach. Controlling the disease locally with surgery and radiation is important, as is using chemotherapy to address the high probability of metastasis.

ASAC needs aggressive surgery with adequate margins; a poorly planned surgery (or biopsy) can actually spread the disease locally, compromising a successful outcome. For this reason, I strongly recommend running advanced imaging to thoroughly plan the biopsy or surgery ahead of time, especially for larger tumors. MRIs and CT scans can provide good detail about the primary tumor, the extent to which it has invaded local tissues and whether it has spread to regional lymph nodes (and which ones).

During the surgery, up to fifty percent of regional lymph nodes (typically the sublumbar lymph nodes) can usually be removed completely, although the surgeon will not know whether removal is possible until the surgery takes place. Removing metastatic lymph nodes can improve survival times, so this is important.

The conventional treatments Dr. Ettinger recommends for perianal and anal sac tumors 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
.

Sometimes, the anal sphincter must be partially removed during this surgery. This sphincter is the round muscle that literally keeps the anus closed between defecations, so removing it can make some owners worry that their dogs will become incontinent. This may be true for a little while after surgery, but dogs can lose up to 50% of the sphincter and still rehabilitate themselves, once they have healed. Fecal incontinence is usually not a concern for the long-term.

For ASAC treated only with surgery, median survival times are ten to eighteen months. Including surgery in your dog’s treatment time is considered a must, because studies show that dogs who receive surgery fare better than those who do not.

If your dog has increased ionized calcium levels, survival times are shorter, usually six to nine months (note that some studies failed to show this was a negative predictor). The ionized calcium levels typically go back to normal levels after the surgery. Check them periodically to monitor for recurrence and/or spread.

If the surgery results in incomplete margins, radiation should be used to control microscopic disease and prevent recurrence and/or regional spread. Your radiation oncologist may also want to treat the sublumbar lymph nodes to prevent or delay metastasis. Keep in mind that there are side effects to radiation. In this area, the skin and the lining of the colon and rectum are affected, so your dog may have burning, irritation, inflammation and diarrhea for two to four weeks after treatment. Late side effects can also occur months or years later; in this area they tend to be chronic diarrhea, straining to defecate, scarring of the tissue or stricture (narrowing) of the anus.

Palliative radiation can be used for inoperable ASAC tumors, or for disease that is confined to the regional lymph nodes. This use of radiation may slow the progression of the disease, but is rarely curative. Early side effects are less common than with a full course of radiation therapy.

Because ASAC is so metastatic, chemotherapy is recommended to delay the spread. The most effective drugs as of this writing are carboplatin, mitoxantrone, and Adriamycin, and others are being evaluated. Piroxicam and Palladia are also under evaluation; check with your oncologist. Some recent studies show that survival times may approach two or even two and a half years when all three modalities are used to treat ASAC (surgery, radiation and chemotherapy). Another, smaller study of afflicted dogs with no distant metastasis, showed that surgery followed by daily, fractionated radiation therapy and mitoxantrone chemotherapy produced a survival time of thirty-one months or nearly three years. If your dog has ASAC with no distant metastasis and you can afford to use all three therapies, I strongly recommend considering it. (The exception is if clean margins are achieved surgically – in these radiation may not be recommended.)

“There is always hope! You should learn everything you can about the type of cancer your fur baby has and then no matter how much or how little time you have, live each day for just that day. Yes, you will have ‘down’ days but don’t brood on them, just know that they will happen. Look at the diet you are feeding your friend, and see where you can make it better, variety is very good for them too just as it is for you. Read and learn everything you can: the treatments, the medications, supplements and diets, because it is you who are the closest to your friend, and you know what is best for your dog.”

- Shirley, Salem, Oregon

Chemotherapy is sometimes used as a standalone therapy for inoperable ASAC tumors; this is considered palliative care and is associated with shorter survival times of seven months.

If your dog has elevated blood calcium levels, an injectable medication called pamidronate can be given intravenously to lower them and decrease associated symptoms. Prednisone can also be used.

Stool softeners may be helpful for dogs with intrapelvic masses that cause obstruction of the pelvic canal.

Perianal and anal sac tumors are extremely variable in their outcome – from curable to highly metastatic. Nevertheless, I consider even the aggressive ASAC a treatable cancer, when combined therapies are used. These can extend life and make dogs much more comfortable than they are at diagnosis.

M
elanoma is a common dog cancer that occurs in darkly pigmented skin. The most common forms are oral, digit, and skin, although melanomas can appear anywhere melanocytes, the cells they occur in, are located in the body.

Oral malignant melanoma (OMM) is the most common oral tumor in dogs, accounting for 30-40% of all oral tumors. It is highly metastatic and has often spread to distant sites away from the tumor by the time of diagnosis. Digit melanoma, which occurs on the toes, is also metastatic, although less so than the oral type. Although melanoma which occurs in the skin is very malignant in humans, it is typically benign in dogs.