About chemotherapy: Dr. Michelle Wall (Board Certified-Oncology)

Chemotherapy in Pets

There are numerous preconceived beliefs regarding the use of chemotherapy for our four legged family members.  Most of us have unfortunately either personally experienced chemotherapy, or have witnessed a family member or close friend undergo treatments.  Since many of our first time clients assume chemotherapy would be a dreadful experience for their pets, and therefore are understandably apprehensive to choose this route for their furry family members, we decided to discuss chemotherapy in pets.

What is chemotherapy?

Chemotherapy drugs are compounds that are toxic to cancer cells.  Chemotherapy may be given by intravenous (in the vein) or subcutaneous (under the skin) injections, or by mouth.

How does chemotherapy work?

Cancer cells generally multiply very rapidly.  Most chemotherapy drugs work by damaging the ability of these rapidly growing cells to divide, eventually killing them.

What are the benefits of chemotherapy? 

  1. Chemotherapy is the most effective single treatment for some types of cancer, offering the best opportunity for remission while at the same time preserving a good quality of life.  A good example of this type of cancer is lymphoma.
  1. Chemotherapy is often recommended after surgical removal of a malignant cancer.  The purpose of chemotherapy in this setting is not only to prevent recurrence of the cancer at the original site, but also to prevent spread (metastasis).  Examples of cancers in which chemotherapy is used in this way is hemangiosarcoma of the spleen in dogs and malignant bone tumors in dogs.
  1. Occasionally, chemotherapy will be used alone for the treatment of cancers in which it is not possible to perform surgical removal or radiation therapy, or in cancers that have already metastasized.   In most cases, the goal of treatment will not be to cure the cancer, but rather to improve that patient’s quality of life temporarily by reducing pressure, bleeding, and/or pain.

Are there risks or side effects associated with chemotherapy?

There are risks involved with any type of treatment for cancer.  Some normal cells will be injured and killed by the chemotherapy.  Side effects may be apparent because of these normal cells being killed.  However, these side effects are usually outweighed by the benefits of killing the cancer cells.

Dogs and cats tolerate chemotherapy much better than human patients do.  We do not use as intensive of a dosing regimen as is utilized in human oncology.  The two side effects encountered most commonly in our animal patients are toxicity to the gastrointestinal tract and toxicity to the bone marrow.  Normal cells in both of these areas divide very rapidly, so they are more susceptible to the toxic effects of the chemotherapy.  When the cells lining the gastrointestinal tract are affected, the result may be vomiting and/or diarrhea.  Most patients will experience this side effect at least once or twice during their course of chemotherapy treatment, but the symptoms are usually mild and can be overcome with supportive care at home.  White blood cells are cells of the immune system responsible for fighting infections.  The bone marrow produces these cells (called progenitor cells).  If these progenitor cells are damaged, the patient’s white blood cell count may drop low enough to result in an increased susceptibility to infection.  Even bacteria to which a patient would normally be resistant can cause serious illness in this situation.  White blood cells are therefore monitored very carefully.

Hair loss in cats and dogs receiving chemotherapy is usually very minor, with some notable exceptions.  If you own a poodle, Old English sheepdog, schnauzer, puli, lhasa apso, shih tzu, bichon fries, terrier, or maltese, you should expect that your pet will lose a significant amount of hair during the initial stages of chemotherapy.  However, the hair that is lost will grow back after your dog’s course of chemotherapy has been completed, or once the treatments are being administered less frequently.  Cats do not usually lose hair, although many will lose their whiskers.

Is chemotherapy expensive?

Treatment of cancer with chemotherapy can be costly.  It involves the use of the same drugs to treat human cancer patients, and many of these are expensive.  In addition, your pet will benefit from the expertise of several highly trained health care professionals.  The exact cost of chemotherapy varies with the size of the animal, the number of treatments, and the drugs being administered.

Is it safe for me to be around my pet during the time he/she is receiving chemotherapy?

Generally speaking, the risk f a person becoming exposed to significant amounts of chemotherapy as a result of handling their pet is very low.  We do not recommend changing you or your pet’s lifestyle as part of chemotherapy treatments (i.e. do not ban your pet from sleeping with you if this is part of their normal routine).  Some of the chemotherapy drugs that your pet may receive may be found in trace amounts in their urine or feces for 1-2 days after administration.

The most important goal is quality of life for your family member during the entire chemotherapy protocol, and after.



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