The Dog Cancer Survival Guide (92 page)

The nature of the lymphatic system is movement, which is why lymphoma spreads so quickly, and so widely. This is why I strongly recommend that new lumps in a dog’s body be tested, measured and recorded in the dog’s records for later comparison.

Lymphoma is highly treatable if caught early, so I recommend getting suspicious lumps checked out with a fine needle aspirate to determine if cancer is present. This is especially true when the dog is already not feeling well, or more than one lymph node is enlarged. No one – not even experienced oncologists – can be sure that a suspicious lump is benign, just by feeling it.

Lymphoma can usually be confirmed with this fine needle aspirate. A lymph node close to the surface of the skin is selected, as it is safer to access and does not require sedation or surgery. Typically, organs are not aspirated, especially if their appearances on ultrasound images are normal. On the other hand, if peripheral lymph nodes are normal on exam and these organs are abnormal on ultrasound, they will need to be aspirated to make the diagnosis. Because there are so many places lymphoma can occur, the aspiration site is decided on a case-by-case basis.

If the aspirate comes back “inconclusive,” a biopsy will be done. If either the aspirate or the biopsy comes back positive for lymphoma, I recommend starting treatment immediately; that day, if possible. With many other cancers, owners may have a few days to deliberate treatment options. In the case of fast-moving lymphoma, any delay can cause problems. Once positive results on the aspirate or biopsy are received, I recommend you see an oncologist as soon as possible, and that you be prepared for her to recommend treating the cancer on that day or the next.

I strongly recommend consulting with an oncologist when your dog has lymphoma, because most have successfully treated many, many dogs with this disease. By “successfully,” I mean dogs have an excellent quality of life and significant life extension.

The next step an oncologist will take is to run tests to determine how far the lymphoma has advanced, or what stage it is in. These tests are critical to developing the best treatment plan, custom-tailored to your dog. Tests may include blood work, urine tests, chest X-rays, abdominal ultrasound, immunophenotyping (testing for whether B-cells and/or T-cells are malignant) and, sometimes, a bone marrow test.

These tests are useful because knowing the stage of the cancer can help in gauging survival times. In addition, these tests provide a baseline, so that as treatment progresses, we can observe how the lymphoma is responding. Careful examination and thorough staging can help your oncologist decide how to treat the lymphoma, and you to decide whether to treat it.

One thing I look for in particular is a large “tumor burden” – in other words, a lot of lymphoma showing up in nodes, organs, and/or the bloodstream. If the patient has a large tumor burden, he is at risk for developing “acute tumor lysis syndrome” within forty-eight hours after the first chemotherapy treatment.

Ironically, this syndrome arises because the chemotherapy is very effective for lymphoma. As massive numbers of cancer cells die, the substances that were once inside them (intracellular electrolytes and metabolic by-products such as phosphorous and potassium) are released quickly into the bloodstream; so quickly that the body is overwhelmed. This syndrome is characterized by vomiting, diarrhea, lethargy, collapse, increased or decreased heart rate, heart arrhythmias, renal failure, muscle twitches and breathing problems. This is especially serious when the dog is dehydrated because of not eating and drinking well, or because she has been vomiting from the lymphoma.

When I see large tumor burden in the staging tests, I tailor the dog’s treatment plan to include hospitalization for a day or two, after treatment. This allows us to administer IV fluids prior to and after treatment. The fluids flush out the system and remove the metabolic wastes from circulation. Typically, dogs do not need to be hospitalized for subsequent treatments.

If a dog does not have a large tumor burden, this kind of reaction to chemotherapy during and immediately after treatment is rare, as is the need for hospitalization. Staging tests and examinations help determine which dogs are at risk.

As useful as these tests are, they can cost over $1,000 – and they do not treat the cancer, only tell us more about it. If you ultimately decide not to use chemotherapy to treat the lymphoma, these extra tests could seem like a waste of money. If you have received a positive biopsy or aspirate, and are not sure that you want to treat the lymphoma with chemotherapy, tell your oncologist about that possibility. If owners tell me this, or if they tell me that funds are limited, I may advise them to skip some tests or even staging altogether and, instead, put that money toward treatment.

There is a test available from PetScreen called the Canine Lymphoma Test (CLT). It uses advanced technology to detect certain lymphoma biomarkers, present in a dog’s blood serum, which indicate a high likelihood of lymphoma. Despite the manufacturer’s claim that this test provides a minimally invasive alternative to a fine needle aspirate, in my opinion, it is not necessary for the average dog with lymphoma.

One reason is: using a fine needle to aspirate a lymph node just under the skin is no more invasive than collecting the blood needed for this test.

Also, lymphoma is not technically difficult to diagnose in most dogs, as their lymph nodes are close enough to the skin to allow an easy aspiration. (Lymph node aspiration is no more invasive than the blood draw required for CLT.) CLT may have more use in cases where lymphoma is suspected, but not detectable, after the routine staging I describe above.

This test may have more promise as a monitoring tool used during the monthly rechecks that are necessary after chemotherapy treatments end. It may help to detect lymphoma relapse, although the expense might be burdensome. It is unclear whether using this test to find relapsed lymphoma will lead to longer survival times; if you consider using it, keep these limitations in mind.

There are many factors that we consider in order to arrive at a prognosis. The most consistently predictive factor is the lymphoma’s immunophenotype: does it occur in the B-cells, the T-cells, or both? B-cells typically respond better to chemotherapy than T-cells do, and a dog with B-cell lymphoma survives longer, statistically. Therefore, a dog with B-cell lymphoma has a better prognosis than a dog with T-cell lymphoma.

The second most consistent prognostic factor is the substage: whether the dog is feeling sick at the time of diagnosis. In general, if the dog feels sick at the time of diagnosis, the prognosis is negatively affected.

Substage (a):
no clinical signs related to lymphoma – in other words, the dog does not feel sick, at time of diagnosis.

Substage (b):
there are clinical signs related to lymphoma – in other words, the dog feels sick at time of diagnosis (lethargy, vomiting, diarrhea, weight loss, anemia, fever, etc.).

Lymphoma, like most cancers, has a staging system associated with it. As a general rule, the higher the stage is, the worse the prognosis, although stage is less consistently helpful for prognosis than it may be in other cancers; studies vary. Even so, I include the staging system for your information:

Stage I:
one lymph node is involved.

Stage II:
multiple lymph nodes are involved, on the same side of the diaphragm

(The diaphragm is located between the chest cavity and the abdomen, so lymph nodes above the diaphragm are in the “head end” and those below the diaphragm are in the “tail end” of the body.)

Stage III:
multiple lymph nodes are involved, on both sides of the diaphragm.

Stage IV:
the liver and/or the spleen are involved, with or without stage(s) I, II or III present.

Stage V:
the bone marrow and/or blood are involved, or there is extranodal (outside of the lymphatic system) involvement (for example in the eye or the gastrointestinal tract), with or without stage(s) I, II or III present.

There are several other independent predictive factors we look for to arrive at a prognosis. These are also reliable, statistically proven predictors:

How does the lymphoma respond to treatment?
If the lymphoma responds well to treatment, the prognosis improves. If the lymphoma does not respond well the prognosis worsens. Obviously, your dog’s response cannot be known until treatment is started, so this indicator won’t help you until after treatment begins.

Is the dog on prednisone?
If a dog is already on prednisone before chemotherapy begins, the prognosis worsens. Prednisone tends to activate a protein in the walls of cancer cells, called a multidrug resistance (MDR) pump (see
page 130
). This protein pump kicks toxins out of cells on contact. For cancer cells, chemotherapy drugs are the toxins. If the dog is already on prednisone, this pump may be active, which means that it could interfere with the effectiveness of chemotherapy protocols. This is not an absolute rule, as some of my patients on prednisone, even those with other negative predictors, have outlived others. Ironically, prednisone is often used in chemotherapy protocols, and also has an anti-cancer protocol of its own. The problem is
use prior to starting chemotherapy,
so inform your oncologist if your dog is on prednisone and, if you have to start using prednisone for some other disease, do so in consultation with your oncologist. Despite this negative predictor, I recommend starting treatment, even if your dog is on prednisone already, as any delay in treatment worsens the overall prognosis.

I’d like to pause for a moment to remind you that every dog is different from every other dog, and that every cancer case is different from every other cancer case. Being acquainted with the stages and the predictors can help you nurture more accurate expectations about your dog’s possible outcome. Lymphoma moves quickly and can end a dog’s life in a matter of weeks, if left untreated. However, it is highly responsive to chemotherapy, especially in its early stages.

Much is known about lymphoma in dogs, and there are several published protocols on how to treat it. Because lymphoma is so sensitive to chemotherapy, it is the treatment of choice. The goal of treatment is to achieve a complete remission of the lymphoma while maintaining an excellent quality of life for your dog. I will outline the most important – in my experience, the most successful – protocols below.

Keep in mind as you read my recommendations that there is no “one right way” to treat lymphoma. Every patient is unique, so, the best treatment for one dog and his owner may not be the best treatment for another dog and her owner. As always, consider your preferences, budget, and other factors, as you review your options (hopefully, with your oncologist).

As tempting as it may be to think of these recommendations as “lymphoma recipe” chemotherapy treatments, it is impossible for me to give that to you. Cancer is not predictable. In any given case, in my own practice, I may tweak the starting protocol at each successive visit, in response to the dog’s progress.

The highest remission rates and the longest survival times are achieved with combination protocols, so I will begin with the one with which I have had the most success.

The University of Wisconsin (UW) CHOP protocol is my treatment of choice for just about every dog with lymphoma (except, perhaps, T-cell lymphoma), especially if money is not a concern.

Any multi-drug protocol that combines cyclophosphamide (C), doxorubicin (hydroxydaunorubicin or H), vincristine (Oncovin or O) and prednisone (P) is known as a “CHOP” protocol.
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These combination protocols have had the best success rates, so the nineteen- or twenty-fiveweek protocol, published by the University of Wisconsin, is what I currently recommend.

Over 90% of afflicted dogs go into complete remission on the UW CHOP protocol, usually within the first few weeks. The typical protocol lasts five to six months, and once it is completed and treatments end, the remission typically lasts another four to six months. If a relapse occurs during this treatment-free time, approximately 90% of dogs achieve a second remission when the same protocol is repeated. The median survival time for treated dogs is thirteen to fourteen months from the time of diagnosis.

The rate of complications from treatment is relatively low. Most dogs will experience some sort of digestive upset (vomiting, diarrhea or nausea) at least once or twice during the course of the protocol. These side effects are usually managed with the home care (described in
chapter 11
) and don’t require an office visit. The few (less than 5%) dogs who have more severe symptoms may need hospitalization for IV fluids, antibiotics and injectable anti-nausea medications. Most of these can still continue the protocol, although doses may need to be adjusted or preventive medications used.

Some dogs experience low white blood counts on these protocols. When this happens, doses may need to be reduced, or treatments delayed, to get those white blood cell counts back up (see
page 131
). Interestingly, a recent study found a silver lining in this scenario: dogs with moderate to severe low white blood cell counts during chemotherapy treatment actually experienced longer first remissions. This suggests that the dosage reductions and treatment delays did not affect the length of the first remission (longer first remissions indicate longer survival times). On the flip side, dogs that did not develop low white blood counts had shorter first remissions (which are associated with shorter survival times). Would these dogs have done better in the long run with higher doses of chemotherapy, and lower resulting white blood cell counts? This is an intriguing area that needs more study. I cannot say for sure that using higher doses with the goal of inducing low white blood counts will definitely translate to longer remissions and survival times; however, based on this study I do consider that strategy on a case-by-case basis with my own patients. If this approach is interesting to you, I would discuss it with your oncologist.