Chemotherapy

WHAT IS CHEMOTHERAPY?

The use of a drug or chemical to treat any illness is
chemotherapy, but this term commonly refers to the use of drugs
in the treatment of cancer. The goal of chemotherapy in
companion animals is either to increase the life span or to
improve the quality of life for the animal with cancer.

HOW DOES CHEMOTHERAPY WORK?

Cancer can be defined as a rapid, uncontrolled growth of cells.
Anticancer drugs work by blocking cell growth and division.
Different drugs interfere with different steps in these
processes. In many cases, a combination of drugs is the most
effective way to kill the cancer cells.

HOW IS CHEMOTHERAPY GIVEN?

Most anticancer drugs are given by mouth or by injection. The
route chosen depends on the type of drug and the type of cancer.

HOW LONG WILL MY PET RECEIVE CHEMOTHERAPY?

The length of time and frequency of drug administration depend
on the kind of cancer being treated and how well the therapy is
tolerated by the patient. Treatment may be given daily, weekly,
or monthly.

AM I AT RISK OF EXPOSURE TO THESE DRUGS?

Yes. Most anticancer drugs are very potent and must be handled
with care. Some are “carcinogens” and can cause cancer with
prolonged exposure. With orally administered drugs, it is
important that the pills or capsules are kept out of reach of
children in childproof containers. When handling these drugs,
the owner should wear latex or polyvinyl gloves to avoid
unnecessary exposure. With oral and injectable drugs, the urine
and feces of the animal may be contaminated with active drug
compounds for several days after administration.

Always avoid contact with the urine and feces of animals
receiving chemotherapy. Wear latex or polyvinyl gloves to clean
up accidents or the litter box. Rinse exposed surfaces well.

WILL MY PET EXPERIENCE SIDE EFFECTS?

Maybe. Veterinarians try to choose drug doses and combinations
that cause the fewest side effects. Ideally, the animal
receiving chemotherapy does not even realize that he or she is
ill. The drugs used in chemotherapy, however, are extremely
potent and side effects can occur. The potential for side
effects must be balanced against the benefits of the
chemotherapy and the side effects of the cancer if left
untreated. Choosing chemotherapy for your pet is an individual
decision.

WHAT KINDS OF SIDE EFFECTS OCCUR?

Side effects arise because the normal cells in the body are also
exposed to the anticancer drug. The most sensitive normal cells
are found in the blood, gastrointestinal tract, skin, and
reproductive system. Consequently, potential side effects
include infection, bleeding, decreased appetite, vomiting,
diarrhea, thin haircoat or skin color changes, and sterility.
Rare side effects associated with specific drugs include bladder
discomfort, kidney damage, and heart failure. The most serious
side effect is overwhelming infection leading to death.

WHAT ARE THE MOST COMMON SIDE EFFECTS?

The most common side effect reported by owners is that the pet
seems to be “off” for a day or two. This might mean that the pet
has slightly less energy or seems less excited than normal about
eating. Less commonly, the pet may skip a meal or two, have one
episode of vomiting or diarrhea, or seem lethargic.
Unfortunately, there is no way to predict which pet will develop
the most serious reactions. The animal receiving chemotherapy
needs to be watched closely and taken to his or her veterinarian
at the first signs of illness.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.