The Dog Cancer Survival Guide (113 page)

The conventional treatments Dr. Ettinger recommends for soft tissue sarcoma 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
.

Although surgery is clearly important, there is an increasing move toward a combined treatment of surgery and radiation therapy for narrow or incomplete margins. Most commonly, radiation therapy is started two to three weeks after surgery. A course of radiation therapy after surgery can help to control the tumor locally and prevent recurrence from microscopic cells. Low and intermediate grades of STS may really benefit from this combined approach: 75% of afflicted dogs are still alive, five years later, without tumor regrowth. STS is one of the few malignancies associated with five-year control rates, which justifies the extra expense and involvement of adding radiation treatments in the minds of owners who choose it. If your dog is a candidate for this approach, keep in mind the multiple anesthesia sessions (fifteen to twenty) and the early and late side effects (see
page 125
).

In some cases, radiation therapy may be recommended before surgery, to reduce the size of a tumor that is otherwise inoperable. There are no studies that prove whether pre- or post-operative radiation therapy has better response rates, better local control rates or fewer complications, so the decision is usually made on a case-by-case basis. I find the best outcomes are achieved when the team of specialists includes a surgeon, a medical oncologist and a radiation oncologist. Incidentally, radiation is not used as a sole treatment, because these tumors do not respond well to radiation alone.

STS does not respond well to chemotherapy, either, especially in the primary site. We may use chemotherapy to treat grade III and other high-risk tumors (those with high proliferation markers and microvessel scores) after surgery and/or radiation. In certain cases, the addition of chemotherapy may prevent or delay metastasis and possibly treat existing metastatic disease.

When chemotherapy is used to treat the primary STS tumor, for example a non-resectable tumor, it is considered palliative, not an attempt at a cure. It may shrink the mass a little, which can make the dog more comfortable.

Metronomic, or low-dose oral chemotherapy, has recently been reported to delay recurrence in dogs with incompletely removed low and intermediate grade tumors. Using chronic, low doses of oral cyclophosphamide and piroxicam may be an alternative to post-surgical radiation therapy. In studies, dogs who did not receive metronomic chemotherapy had a median recurrence at seven months, while dogs treated with metronomic chemotherapy reached about fourteen months. Clearly, these statistics are not as impressive as those associated with post-surgical radiation treatments; on the other hand, metronomic chemotherapy is less expensive and does not have the side effects associated with radiation, so therefore may be an attractive option.

Low or intermediate grade STS is treatable, with excellent long term control and survival rates associated with aggressive surgery or combined surgery and radiation treatments. The prospects are worse for a high-grade tumor, which is more likely to metastasize, but treatment and tumor control is still possible. Combining surgery, radiation and chemotherapy can extend life and enhance life quality.

B
rain tumors develop in the tissues of the brain, inside the head. Most grow slowly, and are often found long after becoming well established. While tumors invariably affect the brain’s function, this adaptable organ can often compensate for the damage. This can go on for a long time, until decompensation occurs, which is when the brain can no longer cope. This often happens very quickly, and it may seem as if your dog is very sick “overnight.” Brain tumors are relatively rare in dogs, and very serious. If left untreated, survival times range from one week to two months.

In most areas of the body, there is room for tumors to grow quite a bit before they start to squeeze out normal functioning tissue. In the confined space of the skull, however, tumors can rapidly take up space needed by the rest of the brain. The brain responds to compression with many different kinds of neurologic changes, from personality disorders to seizures.

What makes these tumors so difficult to treat is the lack of a firm diagnosis. Because the brain is hard to access, and biopsies are not commonly done, it is difficult to determine the type of tumor involved or the likely prognosis for your dog. The goal of treatment is to remove the tumor if possible, reduce its size, and relieve the symptoms associated with the mass, including brain inflammation and swelling. A combination of radiation, surgery and chemotherapy may be used, depending upon the tumor’s size and location.

The inability to determine the tumor type, in the vast majority of cases, makes forming a prognosis quite difficult for your vet or oncologist. Left untreated, the prognosis is certainly poor: weeks to months. Brain tumors are named for the type of brain tissue they arise in; common tumors include: meningioma, glioma, choroid plexus tumor, ependymoma and medulloblastoma, to name a few.

Brain tumors develop within normal cells found in the brain or the meninges (three layers that cover and protect the brain and spinal cord). The most common brain tumor is the meningioma, found in the meninges, which accounts for just under half of all cases. The second most common tumor is the glioma, which is found in the glial cells, which surround and protect the delicate neurons in the brain. These are followed by choroid plexus tumors, which develop in the space where cerebrospinal fluid is made; ependymomas, which occur in the lining of the ventricles of the brain; and medulloblastomas, which occur in the brain tissue in the cerebellum.

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

Other cancers, like pituitary tumors, nasal cancers and bone tumors, can invade the brain from their primary locations. Hemangiosarcoma, mammary carcinoma and lymphoma all metastasize to the brain. Although located in the brain, they are not primary brain cancers, and are not dealt with here.

We often classify tumors in other body locations as either malignant or benign, depending upon their cell characteristics when they are viewed under a microscope in a lab. Classifying brain tumors this way can be misleading: all brain tumors are malignant, in the sense that they are life-threatening and devastating, because they grow within the confined space of the skull. Their mass, and the associated inflammation and edema (swelling), compress the normal brain tissue, resulting in neurological changes. Whether symptoms stem from the tumor or the associated compression and/or inflammation, their overall effect is malignant.

There are no known risk factors for brain cancer, and only a few associations. Dogs with brain cancer are nearly always older than five years of age (95%). Studies have shown that dogs with meningioma, the most common brain cancer, have a high proportion of receptors in their cells for the hormone progesterone; both estrogen and progesterone can influence cancer development.

Certain breeds are also at increased risk: Golden Retrievers, Boxers, Doberman Pinschers, Scottish Terriers and Old English Sheepdogs.

Breeds with long, narrow heads, such as Collies and Greyhounds, may be at an increased risk for meningiomas, and dogs with a short snout or flat, pushed-in face, such as Boxers, Pugs and Boston Terriers may be at an increased risk for gliomas.

Brain tumors are often first discovered when the dog starts having seizures, which happens in 45% of dogs with brain cancer. If your dog is four to five years or older and has a seizure, a brain tumor is the most likely cause.

Other owners may notice circling, drunk walking (ataxia), holding the head at a tilted angle, an altered mental status (your dog seems out of it), limb weakness or paralysis, or subtle behavior changes, including aggression. Sometimes the symptoms are much vaguer: increased lethargy or decreased appetite. The symptoms usually affect one side of the body more than the other side (are asymmetrical), because the lesion is usually on one side of the brain.

One of the difficulties with brain cancer is that some tumors develop so slowly that your dog’s brain is able to compensate for the alterations, effectively masking the neurological symptoms or making them so subtle that they are hard to detect. Vague or subtle changes in behavior, happening over many months, for instance, can be easy to overlook by the owner and the vet.

In humans, the first symptom of a brain tumor is a severe, persistent headache, and it makes sense to think that dogs experience some sort of head pain, too. Since dogs cannot tell us directly if they have a headache, they may have other, more subtle ways of sending the message. When looking back, many owners realize that their dog has become less social, more depressed, more irritable or more sensitive to being handled.

Brain cancer is suspected, based on your dog’s age, breed, history of symptoms and neurological examination. The results of a neurological exam can vary based on where the lesion is located in the brain, how extensive it is and how quickly it is growing. A complete exam from a neurologist can usually reveal the area of the brain where the problem is located.