Chemotherapy is a valuable form of treatment for many types of cancer in dogs and cats. For certain cancers, such as lymphoma, chemotherapy is used alone with the goal of achieving remission. Chemotherapy is also often used following surgery or radiation therapy to delay or prevent metastasis (the development of secondary malignant growths at a distance from a primary site of cancer). In some cases, chemotherapy is used to alleviate symptoms and improve quality of life. Our goal during cancer treatment is to improve the health and quality of life for our patients. We never want the treatment to be worse than the disease.
Cancer is defined as the uncontrolled growth of cells. Traditional chemotherapy medications interfere with the growth of cells by blocking various stages of cell division. Some chemotherapy approaches involve preventing the development of new blood vessels that would feed the tumor or blocking growth factors.
Different chemotherapy drugs have different targets, and in many cases, a combination of drugs is the most effective way to kill cancer cells. Since chemotherapy can affect all dividing cells in the body, healthy cells with high growth rates can also be affected. Cells in the bone marrow, lining of the gastrointestinal tract and hair follicles have high growth rates and can therefore be affected by chemotherapy. Therefore, side effects can occur in those tissues, but normal cells are typically better able to recover and repair themselves than cancer cells.
What to Expect
Chemotherapy schedules are tailored to each patient’s needs. Treatments may be given weekly or less often. Most treatments are given in the hospital but some are administered at home.
Anti-cancer drugs can be administered via the following routes, although not all drugs can be administered by every route.
Oral: Given by mouth and absorbed by the gastrointestinal tract
Intravenous: Injected directly into the bloodstream through an intravenous catheter; this is the most common way chemotherapy is administered
Subcutaneous: Injected under the skin
Intralesional: Injected directly into the tumor or surgical site
Intramuscular: Injected into a muscle
Intracavitary: Injected directly into the chest or abdomen
With the drug dosages used in veterinary medicine, most pets experience minimal to no side effects. A small percentage of animals do become ill after receiving chemotherapy. Side effects most commonly occur 2-3 days following treatment but could occur the day of treatment until 10-14 days later.
Potential side effects may include nausea, vomiting, diarrhea, constipation, fever, bloody urine, hair loss. If your pet does experience side effects, medications may be prescribed to alleviate symptoms. Your oncologist may also recommend prophylactic (preventative) medications or alter the drug type or dosage to decrease the likelihood of side effects from subsequent treatments.
Cancer is a disease that can be managed much like other diseases.
Frequently Asked Questions
Will my pet's hair or whiskers fall out with chemotherapy?
Most animals do not experience hair loss. Shaved areas will grow back slowly. Cats may lose their whiskers and guard hairs. Dogs that need to be clipped and groomed, such as poodles, terriers, etc., are likely to have mild to moderate hair loss. The hair loss tends to be worse following treatment with Adriamycin. The hair will re-grow once the treatments have finished. Occasionally the hair will grow back a different texture or color. This is a cosmetic side effect only and does not negatively affect the quality of your pet's life.
Will my pet get sick from chemotherapy?
Our goal at the Veterinary Cancer Group is to provide the best quality of life possible for as long as possible. The drug dosages used in veterinary medicine do not cause side effects in most animals. Despite this, there is a slight risk of side effects and a small percentage of animals may become ill after chemotherapy. Most side effects occur during the first few days of therapy, although they can occur at any time during treatment. If your pet does have side effects, the drug type or dosage will be modified to minimize the chance of side effects reoccurring. Signs of illness can range from a slight decrease in energy and appetite to lethargy, anorexia, diarrhea, and vomiting. Typically, over-the-counter medications are all that is needed if side effects should occur.
Do I need to take precautions regarding myself, my family, or other pets while my pet is on chemotherapy?
For orally administered chemotherapy drugs, it is important that the capsules or pills are kept out of the reach of children. If you are pregnant, trying to get pregnant or nursing, try to arrange for someone else to administer them. Most oral drugs have a protective coating, but we recommend that latex or polyvinyl gloves be worn when handling these medications. It is very important not to cut the pills into pieces or open the capsules, as this can increase the risk of exposure.
Can flea and tick control or heartworm prevention be used while the pet is receiving chemo?
Yes, many of our patients receive Advantage, Frontline, Program or other flea/tick preventative while on chemotherapy. There have been no reports of contraindications using these products with receiving chemotherapy. Do consult with your family veterinarian for their product recommendations.