Cancer is the uncontrolled growth of cells on or within the body. They are either localized to one part of the body as a visible mass (tumor) or spread throughout (metastasis). Cancer is common in pet animals such as the dog or cat and the rate increases with age. Dogs get cancer at roughly the same rate as humans, while cats get fewer cancers. In one survey, approximately 1 of every 250 dogs and cats developed cancer during their lifetime and cancer accounted for almost half the deaths of those pets over 10 years of age. Since the cause of cancer is not known, prevention is difficult. The exception is breast cancer which is largely preventable with early neutering.
THREE RULES FOR MANAGING THE CANCER PATIENT
RULE 1: GET A DIAGNOSIS
Biopsy, Biopsy, Biopsy. A veterinarian can never give an accurate assessment (prognosis) or develop an appropriate treatment plan for the tumor-bearing pet without a complete diagnosis. Knowing the histologic type of tumor gives the veterinarian a sense of the natural behavior of the tumor (how it will grow, where it will go).
RULE 2: EVALUATE THE ENTIRE PATIENT
Remember, there is a pet attached to the tumor. Many times we forget the BIG PICTURE. A thorough evaluation of the pet includes obtaining appropriate laboratory information (blood counts, blood chemistry, urinalysis) and survey radiographic images of the thorax, abdomen, and the tumor site. Additional information may be required depending upon the known natural behavior of the tumor (remember that biopsy you took in Rule 1 - it's extremely important). These tests may include a bone marrow aspirate, electrophoresis of serum or urine, buffy coat smears, more biopsies, ultrasound of a body area, nuclear imaging, serology, virology, or many other procedures. A thorough knowledge of the entire patient is necessary BEFORE an appropriate therapeutic plan can be presented. The goal is to identify or rule out the presence of concurrent illnesses and tumor metastases to regional lymph nodes or other body tissues (lungs, liver, skin, bone, for example). This information is essential not only for treatment planning but also to determine treatment success or failure.
RULE 3: DEVELOP AN APPROPRIATE TREATMENT PLAN
Determine your goal. Is cure possible or should more emphasis be placed on quality of life (or can both be achieved? In general, there are 3 choices facing every family with a tumor-bearing pet:
Choice 1: What Is Best For The Cancer?
In today's world there are basically 2 ways to treat cancer, remove the tumor (with surgery and getting cancer-free edges all around the tumor) or destroy the tumor's ability to grow (using radiation, chemotherapy, or both; maybe in combination with surgery). There are a number of other innovative strategies under development such as immune stimulants, nutriceuticals, and tumor vessel growth inhibitors, but their true ability to control cancer is not yet known or proven (nor the best way to use them in managing cancer patients - in humans or animals). Veterinarians cure a large majority of cancers with surgery. Those that cannot be completely removed and have not yet spread to other body sites can be cured with additional measures (radiation, chemotherapy, etc) no differently than in people. Common concerns are about "how my pet look without a leg, a lower jaw, a rib?" or "how much is radiation therapy, and what are the side effects?". Every pet owner whose loved one has cancer faces these and other questions. There are no easy answers. However, if the objective of the planned treatment is to attempt a cure of the cancer, surgery with or without radiation has to be strongly considered. Talk to a Veterinary Oncologist!
Choice 2: What Is Best For The Pet?
Remember, for most families, quality of life for their pet is more important than the pet’s remaining quantity of life. Remember, cancer is "uncontrolled growth". If the abnormal growth cannot be removed from the body or controlled with localized radiation therapy, it is entirely appropriate the use medications (anticancer drugs, nutritional supplements, pain control medications, anti-cough or anti-nausea medications, and many others) to maximize the quality of life of the cancer-bearing pet. To "control" the "uncontrolled growth" of cancer, anticancer drugs (chemotherapy) are used. The goal of chemotherapy is not to cure the cancer but to slow down the growing phase of the cancer. Yes, many cancer cells are killed with chemotherapy and tumor shrinkage can be observed; however, it is impractical for most situations to expect that every cancer cell will be killed by any chemotherapy protocol or strategy. With chemotherapy, the more drugs that are used, the more often they are given, the more cancer cells that are killed. Therefore, to significantly decrease the burden of cancer and increase the lifespan of the pet, combination chemotherapy protocols that prescribe drugs every 2, 3, or 4 weeks throughout the remaining lifespan of the pet should prolong the pet's survival. Obviously, most chemotherapy drugs do not know a normal cell from a cancer cell, thus, more drugs given more often results in the possibility of more side effects. If the goal is to provide more quality of life than quantity of life, a fewer number of drugs at lesser doses given less often will still slow down cancer just not as much!
Choice 3: What Is Best For The Family?
It is entirely appropriate not to treat cancer in pets. In fact, in some situations, we should not recommend cancer therapy. However, just because we are not controlling the cancer does not mean we cannot provide the pet a comfortable life. When this cannot be accomplished, we should strongly urge pet owners to consider the choice of euthanasia. It is important to have a support group during this process. Please rely upon the good advice of family and friends during this difficult time. In addition, there are many pet owners who are willing to share their positive and negative experiences. It is essential to provide adequate nutritional support, pain control, and other measures that ensure the pet's good quality of life. Quality of life is very subjective. Everyone has an opinion. Ask for opinions and listen to them!!!! Then make your best choice. Hindsight is 20:20 but if you follow the above rules - get a diagnosis and evaluate the whole patient - then you should have plenty of information to make the best choice available at that time.I hope this information provides some insights towards our approach in managing the veterinary cancer patient. Always consult with a Board Certified Veterinary Oncologist. Use a team approach and allow your pet owners to participate in the team. Cancer is a battle that can be won - engage into the fight, but realize when it is time to retreat.
Drs. King, Carreras and Endicott are available to consult with your veterinarian if they have oncology cases requiring further diagnostic workup or treatment.
