The Dog Cancer Survival Guide (91 page)

Empowered and educated clients make the best decisions, so, the more you know and understand about your dog’s cancer, the better off you’ll be.

When Dr. Dressler first invited me to co-author this book, I did not say yes immediately. I’m very busy with my practice, and my husband is also a very busy veterinarian. Add two children under the age of five, and you get an idea of my life. I even had to think carefully about whether contributing to this book was worth the time and effort necessary.

After reading the first edition and reviewing Dr. Dressler’s blog, my loyalty to dogs and to my profession inspired me to say yes. I’m not a veterinarian by accident, and I didn’t become an oncologist because it’s easy. I work with animals because I love them, and I practice oncology because I believe in it. I’m also a dog lover, just like you are.

I have participated in this entire book, from cover to cover, including
Chapter 11
(which is also about conventional cancer treatments). As you can tell from reading the sidebars, I don’t always agree with Dr. Dressler. Even so, I respect his work and know him to be a well-trained Cornellian (Cornell University grad). He doesn’t recommend voodoo, and he’s exhaustive in his literature research. He uses science to back up his work, and only recommends what has been shown to have value.

Important: if you haven’t yet read the rest of this book, make it a priority to do so. There is important information there that isn’t covered in this section.

I see dogs with cancer day in and day out, and I see the toll the diagnosis and treatment takes on owners who worry over their dogs. My heart goes out to each and every one, and to you, the reader, as well. Here’s what I tell my own clients about worry:

“Worry doesn’t help your dog get better. It’s wasted energy. Try not to worry about outcomes, or whether he will live up to or exceed the statistics. Let me worry about those things – that’s my job! Meanwhile, you should be focusing on caring for your dog in ways I can’t: enjoying your time together. Reporting back to me how he’s doing is enough work for you – leave the rest to me.” I hope the information in this book allows you to worry less, and enjoy your time with your dog more.

L
ymphoma is an aggressive cancer; it occurs in the lymphatic cells and quickly spreads throughout the body. Also called lymphosarcoma and malignant lymphoma, it is called non- Hodgkin’s lymphoma when it occurs in humans.

Despite its aggressive nature, oncologists consider lymphoma one of the most treatable of canine cancers because it is highly responsive to chemotherapy. Dogs receiving chemotherapy have a median survival time of thirteen to fourteen months. During that time, most dogs live well, even during the chemotherapy treatments.

Early detection and treatment are vital to this happy outcome.

Without treatment, symptoms worsen and interfere with normal life functions, such as eating and drinking. Lymphoma negatively affects vital organ function. Most affected dogs will succumb to the disease in one month, on the average, while for some it can be a matter of days.

Lymphoma occurs in tiny cells called lymphocytes, specifically in the T-cells and the B-cells, which are part of the immune system. These specialized white blood cells circulate in the clear body fluid called lymph, which flows through the lymphatic system. T- and B-cells, along with other lymphocytes, are responsible for fighting and destroying bacteria, viruses and other foreign substances in the body. When these normally helpful immune system cells undergo a malignant transformation and become cancerous, they lose their ability to function normally and are called lymphoma. Lymphoma can develop in T-cells, in just the B-cells, or in both.

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

To understand this cancer, you must first grasp the complexity and vastness of the lymphatic system. It is a vast network of tubes and tissues, similar to the circulatory system in structure: large vessels lead to smaller and smaller ones, as they branch into most body tissues. Inside the network is the lymph, which carries the lymphocytes, as well as nutrients, to the cells, and wastes away from them.

If a map of the lymphatic system looks a little like a subway map, then the lymph nodes are the subway stations. Lymph nodes (or lymph glands) are “filters,” located throughout the body. As the lymph flows through, the nodes trap bacteria, viruses and other foreign substances, so they can be contained and destroyed by lymphocytes. Organs that contain a lot of lymphatic tissue are sometimes called lymphoid organs: examples include the spleen, thymus and bone marrow. Lymphocytes also originate in these tissues.

Lymph nodes can become swollen when there is an infection (viral, bacterial, etc.) in the body, because they are filled with white blood cells, including B-cells and T-cells, fighting and destroying the infection. You are probably already familiar with this phenomenon from your own life experience, especially if you have ever had strep throat. As you may remember, this infection creates “swollen glands” in the neck, which can be felt through the skin and may cause pressure or discomfort in the throat. These glands are actually lymph nodes.

Lymphoma is thought to start (and is often first detected) in the lymph nodes. However, in some cases, it is not detectable in the nodes, but in other places, such as the kidneys or central nervous system. Regardless of where it begins, lymphoma is, by definition, a systemic cancer, one that is everywhere in the body, because lymphocytes circulate everywhere the lymph goes. This spreading nature also means lymphoma tends to progress rapidly.

About 80% of dogs with lymphoma have the “multicentric” form, in which multiple lymph nodes are cancerous. Often, the first involved lymph nodes are on the outside of the body, just under the skin. As lymphoma progresses, it can also involve the internal lymph nodes in the chest and abdomen, and also the liver, spleen and bone marrow. Less commonly, lymphoma will spread to the digestive tract, skin or nervous system.

Advanced lymphoma can infiltrate the bone marrow, where blood cells are produced. When this happens, blood cell production can be affected. As the cancer fills the space inside the bone, normal blood cells become crowded, resulting in low red blood cell count (also called anemia), which leads to low energy; low white blood cell count, which can lead to infections; and low platelet count, which leads to blood clotting difficulties. Sometimes only one cell line is affected, sometimes all three.

A few specific breed lines, or families, of Rottweilers, Otter Hounds and Bullmastiff have been reported to be genetically predisposed for lymphoma, which means the genes that cause lymphoma can be passed down through their breed lines.

Studies also show that some breeds are generally at an increased risk for developing lymphoma. These include the Boxer, Basset Hound, St. Bernard, Scottish Terrier, Airedale, Labrador Retriever and the Golden Retriever.

Those same studies show the following breeds at decreased risk: Dachshund, Pomeranian, Pekingese, Toy Poodle, Chihuahua and Brittany Spaniel.

Intact (non-spayed) females also appear to be at decreased risk for lymphoma.

In 1994, a study linked herbicides (particularly 2,4-D) and canine lymphoma. However, a subsequent study re-analyzed the results and failed to confirm them. For this reason, the jury is still out on whether herbicide exposure creates a proven risk for developing lymphoma.

Other environmental factors are reportedly associated with canine lymphoma, including electromagnetic radiation exposure (like the exposure from high voltage power lines), proximity to industrial areas and exposure to paints or solvents.

The major sign of lymphoma is one or more enlarged lymph nodes. These are often discovered by the owner while petting the dog. There are several common sites for these masses, including under the jaw, in front of the shoulder and behind the knee. Because many dogs are otherwise healthy in the early stages, swellings under the skin may be the first sign that something is wrong.

Swollen lymph nodes typically feel firm and can be moved back and forth under the skin. They are generally not painful to the touch, and your dog will usually not seem to mind if you touch them. If lymphoma is present, lymph nodes will typically increase in size rapidly over the span of weeks, or even days. As the nodes grow, larger masses may feel more fixed, or anchored, in place.

Sometimes, cancerous lymph nodes can hide deep in the body, where they cannot be felt through the skin. When organs with a lot of lymphoid tissue, such as the spleen, liver or thymus are involved, there may be additional symptoms specific to those organs. For example, if the skin is involved, dogs may have ulcerated, oozing skin lesions, usually in multiple locations. If lymph nodes within the chest or lungs are involved, the dog may cough or have difficulty breathing.

Sometimes, a palpably swollen lymph gland is not the first sign there’s something wrong. An owner may bring his dog in because he is experiencing general symptoms, such as weight loss, decreased appetite, lethargy, vomiting, diarrhea or fever. In these cases, a vet will typically do a physical exam and run routine blood work to discover the cause of the symptoms. The vet may find a lump during the physical exam.

Even if she doesn’t, elevated blood calcium levels may show up in the blood work, warning her of the possible presence of lymphoma. Blood work can also be quite normal, even in advanced lymphoma.

Elevated blood calcium levels are associated with both B-cell and T-cell lymphoma, particularly with T-cell lymphoma. This is, in part, because cells in a special lymph node in front of the heart, called the mediastinal lymph node, can produce a hormone, which raises blood calcium levels. This special node cannot be seen or felt on the surface of the body, so, the owner would not have known it was enlarged.