Cancer Chemotherapy for the Veterinary Health Team

Kenneth Crump, Douglas H. Thamm, Kenneth Crump, Douglas H. Thamm

• Publisher: Wiley-Blackwell
• Year: 2011
• Print ISBN: 9780813821160
• eBook ISBN: 9780470960059
• Edition: 1
• Topic: Medicine
• Subtopic: Veterinary Medicine

Cancer Chemotherapy for the Veterinary Health Team is a clinically relevant and practical manual designed as a guide for the safe and effective administration of cancer chemotherapy. Coverage includes patient assessment, chemotherapy equipment, drug preparation, safety considerations, handling, administration, waste disposal, and management of chemotherapy side effects. An alphabetical listing of common chemotherapy agents offers information on their uses, indications, and toxicities, as well as administration guidelines for methods, routes, and speeds.

With background information for effectively communicating with clients, including coverage of veterinary cancer surgery and radiation therapy, the book provides specific strategies that address the challenging emotional issues surrounding the diagnosis and treatment of cancer in pets. With particular insight into the technician's role, Cancer Chemotherapy for the Veterinary Health Team is a must-have reference for any practice offering chemotherapy.

1

Dispelling the Myths of Animal Cancer and Its Treatment

Douglas H. Thamm

Key Points

• Cancer is a disease we can sometimes cure.
• The four most dangerous words in cancer treatment are “Let’s just watch it.”
• Obtaining a diagnosis prior to surgery is important.
• Often, the part of the tumor that we can see and feel is only the “tip of the iceberg.”
• Pets experience chemotherapy differently from humans.
  • Fewer and less severe side effects
  • Most dogs and cats do not lose a lot of hair from chemotherapy
• The sooner we start chemotherapy, the better chance the drugs have to do their job.
• Radiation therapy is a form of local therapy.
  • Side effects like nausea, fatigue, or bone marrow suppression do not occur.
  • Pets are not radioactive after treatment.

Introduction

There is a great stigma attached to a diagnosis of cancer. It is natural for owners of pets with cancer to relate cancer treatment in animals with the experiences they have had with their own treatments, that of their friends, or their family members. Understanding how cancer treatment in animals differs from cancer treatment in humans is critical when informing owners about cancer and discussing treatment options. Pet owners want to make an informed decision when selecting treatment for their dogs or cats with cancer, and the veterinary technician is often called upon to help answer these questions for the owners.

This chapter describes many of the common questions that owners have about animal cancer and its treatment, and some ideas on how to answer those questions. It is presented in a “question-and-answer” format, with explanations and additional information following the answers.

General Information, Pretreatment Diagnostics, and Staging

Client: Is cancer really a problem in animals?

Technician: Unfortunately, yes. It is the leading “natural” cause of death in adult dogs and the second or third leading cause in cats. Up to 50% of dogs and 30% of cats will be affected by some type of tumor in their lifetime.

Client: Why does it seem like there is so much more cancer in pets these days?

Technician: Better health care = longer life. Cancer is an old-age disease, and more pets are living long enough to get old-age-related illnesses.

Explanation

We are getting so good at managing other husbandry-related conditions in our pets (nutrition, infection, parasites, keeping pets indoors and on leashes) that they are now living long enough to develop more old-age conditions, such as heart disease, kidney disease, endocrine disease, and cancer. Furthermore, now that there are more cancer specialists and options for treating cancer in pets, it is being reported more frequently.

Client: Did something in the environment play a role in Sparky’s cancer? Was I feeding the wrong food?

Technician: For most forms of cancer, we don’t know of any specific causes.

Explanation

There have been some relationships suggested between certain types of cancer and the environment. For instance, some suggest a relationship between canine lymphoma and certain farm chemicals or living in urban areas. Canine mesothelioma has been linked to asbestos. Second-hand smoke has been a suggested contributor to feline gastrointestinal lymphoma. But in most cases, such associations do not hold up to further investigation. Thus, based on what we currently know, food additives, lawn chemicals, pesticides, or cosmic rays do not seem to significantly increase a pet’s risk of most cancers.

Client: What is the difference between “cancer” and “tumor”?

Technician: There is no practical difference. Both refer to abnormal masses in the body that occur as a result of cell growth that has become disorganized and no longer responds to the normal signals telling them to stop growing.

Client: What is the difference between “benign” and “malignant”?

Technician: Malignant tumors are those that have the ability to invade surrounding tissues deeply and/or spread to other parts of the body. Benign tumors do not spread and do not invade very deeply. Small surgery is much more likely to permanently fix a benign tumor than it is to fix a malignant tumor.

Client: Why should I treat my dog’s cancer?

Technician: Cancer is a disease that we can sometimes cure. Diseases like heart disease, diabetes, and other endocrine diseases, as well as cancer, can all be thought of as chronic diseases. We treat many animals with chronic diseases that are never cured. Even in cases where cure is unlikely, there are many ways we can extend a pet’s excellent quality of life with treatment.

Client: Why can’t we just watch the mass and see what happens?

Technician: The four most dangerous words in cancer treatment are “Let’s just watch it.” The sooner we know what this is, the sooner we can begin appropriate treatment.

Explanation

Owners may question why a fine needle aspiration or biopsy of a mass needs to be performed, rather than simply monitoring the mass for change. In general, delay in diagnosis only increases the difficulty of treatment because delay allows the tumor to grow. This may mean a larger, more complicated, more risky, or more expensive surgery. Larger tumor size is associated with worse outcomes for several important veterinary cancers. The lump you are dealing with may be benign, but if it is malignant, the time to find that out is now.

Client: Doesn’t performing a fine needle aspiration or biopsy make the tumor “angry” and increase the risk of spread?

Technician: NO. There is no risk of increased spread from a fine needle aspiration or biopsy.

Explanation

Exceptions to this rule are the following:

(1) Some mast cell tumors may become “inflamed” following a fine needle aspiration due to histamine release, although this does not, in any way, increase the spread. This is rarely serious and can be treated or prevented with an antihistamine, such as diphenhydramine.

(2) Needle aspiration/needle core biopsy of splenic and bladder masses is not recommended due to the risk of local tumor dissemination in the abdomen and/or seeding of the biopsy tract. In these situations, tumor cells can seed either the abdominal cavity after bleeding (spleen) or the body wall as tumor cells are dragged through it by the needle (bladder). Cytocentesis for urine collection in patients suspected or known to have bladder cancer should likewise be avoided.

(3) It is important that needle aspirations and biopsies of cutaneous/subcutaneous masses are planned so that the biopsy tract can be removed when the tumor is removed. This will prevent regrowth along the tract.

Client: Why don’t we just take the tumor off? Why do we need to do a fine needle aspiration or biopsy first?

Technician: Knowing what we are dealing with before surgery lets us know how big a surgery we need to perform, and whether there are any tests that should be performed beforehand.

Explanation

Obtaining a diagnosis prior to surgery lets the veterinarian know whether additional tests are indicated prior to surgery and helps to plan the surgical approach. This helps avoid situations like “Why didn’t you take X-rays before surgery?” and “Why should I have to pay for a second surgery if you ‘didn’t get it all’ the first time?” If surgery is used to obtain a diagnosis, it is important that the owner understands that it may only be another diagnostic test. Based on what is learned from a diagnostic surgery, more tests or treatments might be necessary.

Client: We already did surgery. Isn’t that enough? Why can’t we just wait and see if it grows back?

Technician: If a malignant tumor has been incompletely removed (the so-called dirty cut), the likelihood of regrowth may be high. Tumors that grow back can be much harder to treat.

Explanation

Additional treatment, such as more surgery or radiation therapy, is often recommended if a tumor has been incompletely removed. Locally recurrent tumors (tumors that grow back after surgery) are associated with a worse prognosis in certain diseases, such as canine mast cell tumor and oral melanoma, and are suspected of being worse in others. For this reason, if a tumor is incompletely removed, the time to be aggressive is the very first time the tumor occurs.

Client: Why can’t we wait and see if it spreads, instead of treating now?

Technician: The sooner we start chemotherapy, the better chance the drugs have to do their job. Chemothe...

Table of contents

• Cover
• Title page
• Copyright page
• Contributors
• Preface
• Acknowledgments
• 1 Dispelling the Myths of Animal Cancer and Its Treatment
• 2 Cancer Basics
• 3 Preparation for Chemotherapy Administration
• 4 Assessment of the Chemotherapy Patient
• 5 Chemotherapy Handling, Safety, and Disposal
• 6 Workflow for Chemotherapy Administration
• 7 Chemotherapy Agents
• 8 Management of Chemotherapy Side Effects
• 9 Compassionate Client Communication
• Glossary
• Index