The University of Georgia College of Veterinary Medicine

Oncology (Cancer) Service

Chemotherapy

Download this information as a FAQ sheet [PDF]

Chemotherapy is a treatment using drugs that are toxic to cancer cells. Chemotherapy may be given by intravenous (in the vein) or subcutaneous (under the skin) injection or orally. Most chemotherapy drugs work by damaging the DNA of cancer cells. This decreases the ability of these rapidly growing cells to divide, and kills them.

Chemotherapy is the most effective single treatment for some types of cancer, offering the best opportunity for remission (when cancer becomes undetectable) while at the same time preserving a good quality of life. A good example of this type of cancer is lymphoma (also called lymphosarcoma).

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 routinely used in this way are hemangiosarcoma of the spleen in dogs and malignant (cancerous) bone tumors in dogs.

Chemotherapy may be administered to some animals while they are also receiving radiation therapy for the treatment of their cancers. Some chemotherapy drugs are effective in this situation because they increase the ability of the radiation to kill the cancer cells.

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 of these cases, the goal of treatment is not to cure the cancer but rather to improve that patient's quality of life temporarily by reducing pressure, bleeding, or pain.

Potential side effects

There are risks involved with most types of treatment for cancer because some normal cells will be injured and killed by the chemotherapy drugs. 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 generally tolerate chemotherapy much better than human patients do. The side effects encountered most commonly in canine and feline patients receiving chemotherapy are toxicity to the gastrointestinal tract and toxicity to the bone marrow. Normal cells in both of these areas divide very rapidly, so are more susceptible to the toxic effects of the chemotherapy.

When the cells lining the gastrointestinal tract are affected, the result may be vomiting, diarrhea, and loss of appetite. 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 often be overcome with supportive care at home.

Neutrophils (white blood cells) are cells responsible for fighting infection. 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 and even bacteria to which a patient would normally be resistant can cause serious illness in this situation. White blood cell counts of all canine and feline chemotherapy patients are monitored carefully, but rarely a cat or dog receiving chemotherapy will develop a life-threatening systemic infection. If this happened, you might notice lethargy and loss of appetite. The only way to successfully treat these infections is to admit the patient to the hospital and administer intravenous fluids and antibiotics.

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 frise, Yorkshire terrier, maltese, or curly coated terrier such as an Airedale or Welsh terrier, 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 treatments are being administered less frequently. Hair may need to be clipped frequently during chemotherapy to identify veins. This hair may be slow to regrow. Cats usually do not lose their hair, although many will lose their whiskers and long-haired cats may lose their outer coat.

Some chemotherapy drugs can be extremely irritating to the skin and tissues under the skin if they leak outside of the vein during injection. Examples include the chemotherapy drugs vincristine, vinblastine, adriamycin, and mustargen. Severe swelling, ulceration, and inflammation can be seen. However, this complication is rare because all IV chemotherapy drugs are carefully administered through catheters placed in veins. Some chemotherapy drugs have unique toxicities. This will be explained to you if your pet receives one of these medications.

Specific drugs: Download client information PDFs
Actinomycin-D
Carboplatin
CCNU
Cisplatin
Cyclophosphamide
Doxorubicin_Adriamycin
L-Asparaginase
MPP Protocol
Piroxicam
Prednisone
Streptozotocin
Vinblastine
Vincristine

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Surgery

Please visit the Soft Tissue Surgery Service Web page for more information about surgery options.

Information for Referring Veterinarians

Go to the hospital referral page for general instructions about how to make a referral, and to download the general referral form.

The Oncology consultation form [PDF] may be downloaded here.

Funds for Cancer Research and Treatment

Trot for the Cure

Join our amazing cancer patient, Rafter, each year as he and his owner - along with a couple hundred of our closest friends - walk and trot toward a cure with this fundraiser for cancer research in Charleston, S.C.

UGA CaRES for Pets Fund (Cancer Research, Education and Service) / Nicky Fund for cancer research and treatment brochure [PDF]

Doggie Dash: The College of Veterinary Medicine Canine Club holds an annual fundraiser to support research on cancer in companion animals.

This page was last updated March 17, 2008.