The Dog Cancer Survival Guide (31 page)

Am I saying that antioxidants should not be used? No. Mega-doses may be counter-productive, that’s true. But low, supplemental doses of antioxidants such as vitamins A, C and E can have a good effect on the body. For example, in one study, (human) cancer patients were given antioxidants in addition to their regular chemotherapy treatments for six months. Although the doses were lower than the recommended dietary allowance for these vitamins, they still had a statistically significant effect on the patients. After six months, those taking low doses of vitamin C had less toxicity and spent less time in the hospital. After three months on vitamin E, patients experienced lower rates of infection. After six months on B-carotene, patients had a lower risk for chemotherapy toxicity.

These results are remarkable. If
supplemental
low doses of antioxidants can help a cancer patient experience less toxicity from chemotherapy, and fewer days in the hospital, that is an excellent (and relatively inexpensive) outcome.

Many people, including some vets, make the mistake of thinking that if a low dose is good, a bigger one is better – or better yet, a mega-dose. There are many proponents of mega-doses of antioxidants during cancer treatments. I strongly advise against indiscriminate mega-dosing. As we’ve seen, it may actually be desirable to give cancer cells pro-oxidants, which create free radicals, which could push the cell toward apoptosis, or natural death. In these cases, introducing antioxidants to neutralize free radicals may be counterproductive to healing the cancer.

(The one exception may be intravenous doses of vitamin C, given during and after treatments, which have helped a handful of human cancers go into remission, likely because the large doses of vitamin C actually caused a pro-oxidant effect in the body. I have not
personally
found large doses of vitamin C helpful enough to recommend them across the board, but I am not against their use if your vet has had success with them and they are carefully worked into a comprehensive plan. If this is something you are interested in, please consult with your vet about your dog’s case.)

The bottom line is that mega-doses of antioxidants or potent antioxidant formulations could interfere with pro-oxidant therapies that use free radicals to target cancer cells. Supplemental levels, however, have been shown to be helpful with side effects from conventional treatments. Since eating vegetables has been shown to definitively help prevent cancer, using the cancer diet outlined in
Chapter 14
for dietary antioxidants seems to be the wisest course of action, supplemented by a commercial multivitamin that contains regular, low, dietary levels of antioxidants.

This chapter will be upsetting to some guardians. I remember feeling startled and a little guilty when I first started my research. I have dramatically changed the way I care for my own dog, and my patients, as a result of this information.

If you’re feeling down, I hope that you will be gentle with yourself. This is not common knowledge, and it’s all right that you were not aware of it earlier.

It helps me to remember that my dog is always living in the present moment, where the past is past, and the future isn’t here, yet. Just like a dog shakes water off his coat, you, as guardian, can master your emotions, take your new insights, and use them to help your dog now.

E
ven the most experienced and skilled oncologist cannot tell you for sure whether a lump is cancerous, just by looking at it or feeling it. To get a
diagnosis
(determine if cancer is present) we must run at least one test.

Depending upon the diagnosis, we may also need to look for evidence that it has spread, because sometimes it has by the time of diagnosis. What we find will determine the
stage
of the cancer.

Depending upon the cancer type, several different tests may be used to diagnose and stage your dog’s cancer. Please see Dr. Ettinger’s section of this book for details on the typical diagnosis and staging tests for the most common dog cancers.

In order to determine whether a mass is cancerous, we have to run at least one test. A fine needle aspirate may confirm a tumor, and a biopsy is usually necessary to get an accurate diagnosis and enough information to plan treatments.

The first test for malignancy is usually the fine needle aspirate. The vet inserts a very thin needle into the tumor, to draw up a sample of the cells and fluid inside. If the aspirate is taken from an internal organ, the surface area might need to be shaved and disinfected first. The procedure is often done without sedation or anesthesia, because it is usually only slightly uncomfortable for the dog. The entire procedure takes about two minutes, and the needle is only in the dog for a fraction of that time.

This is one of the most common questions I hear from dog owners, and it sounds like a great idea. We would all love a practical, simple way to detect cancer much earlier than we typically do. It would be good to have a screening tool we could use in high-risk breeds, to make a diagnosis, determine a prognosis, and monitor remission during or after treatment.

The ideal test would be very accurate. It would measure markers in the blood, which are only produced by tumors, or by the dog’s body, in response to the presence of tumors. Ideally, a positive result would occur only with patients who have cancer, and never with patients who don’t. On the flip side, a negative result would always occur with patients who do not have cancer, and never with patients who do.

Getting a very accurate test like this is not easy. Inaccurate test results can occur when other, noncancerous health conditions create false positive or false negative test results. If the test doesn’t reflect the state of cancer in the body accurately, it loses some of its value. “False-positive” test results can lead to additional testing or even to unnecessary treatments. False-negative results are also problematic; the patient might go without treatment.

We have not found a tumor marker that has met this ideal standard, which is why we do not yet have a blood test for cancer in dogs. No specific marker has been found which can be used as a practical screening tool for generally healthy dogs and/or for high-risk dogs.

This is a hot topic for researchers, so, hopefully, an accurate and relatively inexpensive test can be developed soon. If or when such a test becomes available, its use will still need to be evaluated on a case-by-case basis, because any test costs money, and the value of the information gathered must be weighed against a whole host of other factors.

There is one blood test available, which detects canine lymphoma markers in the blood, but I recommend its use only in certain cases. You will read about it in the lymphoma chapter, which starts on
page 297
.

The vet cannot tell, just by looking at the sample with the naked eye, what kind of cells are inside, so the fluid sample is put on a slide and examined under a microscope by the vet or a cytologist (someone who studies cells). The sample can often confirm that, yes, cancer cells are present (and sometimes what kind) or, no, cancer is not present, at least not in that sample. The sample might also reveal signs of infection or inflammation.

Lymphoma, mast cell tumors, histiocytomas, and cysts are usually easy to diagnose with a simple fine needle aspirate. Other growths may be harder to diagnose this way because some tumor cells clump together so tightly that the vet can’t create enough vacuum inside the needle to pull them apart and up. Other tumors, especially some connective tissue tumors, don’t shed cells easily, so the sample contains only fluid, and no cancer cells. If there are no tumor cells in the sample that does not mean that the tumor is not cancerous. In these cases, the cytology report will label the test inconclusive, and another method will have to be used to diagnose the cancer.

A fine needle aspirate cannot be used to stage cancer (tell how far it has spread) or grade cancer (predict how aggressive it is) with precision. It only shows whether cancer is present in the collected specimen. This is why we so often need to do a biopsy.