CHEMOTHERAPY FOR DOGS AND CATS:
INFORMATION FOR PET OWNERS
What is chemotherapy? When is chemotherapy used?
Chemotherapy is the use of drugs in the treatment of cancer. It is the treatment of choice in certain types of cancer, such as lymphosarcoma. Chemotherapy may also be used in combination with radiation therapy or surgery when there is known or suspected metastasis (tumor spread).
How does chemotherapy work?
Chemotherapy drugs disrupt the multiplication of rapidly dividing cells, thereby slowing or stopping the growth of cancer cells. Because cancer cells may eventually develop resistance to a drug that is used frequently, different chemotherapy drugs are often used in combination or in sequence.
Will the chemotherapy make my pet sick all the time? Will the treatment be worse than the disease?
Quality of life is our primary concern. We make every attempt to balance effectively treating the cancer with allowing your pet to continue his/her normal lifestyle. If quality of life declines because of treatment, alternative modes of treatment or even stopping treatment should be considered.
What are the possible side effects of chemotherapy? How are they recognized, treated, and prevented?
Most chemotherapy drugs work by attacking rapidly dividing cells. However, they do not distinguish between the normal populations of rapidly dividing cells in the body (such as bone marrow and intestinal lining) from the cancer cells. Thus, side effects can occur due to damage to normal tissue. Not all chemotherapy drugs produce these side effects. Most animals receiving chemotherapy will NOT experience these side effects.
Bone marrow suppression: A low white blood cell count is the most common potential effect of chemotherapy on the bone marrow. Since white blood cells are important in fighting infection, illness may occur if the count is low. Signs may include fever, listlessness, depression, loss of appetite, and vomiting and diarrhea. It is also possible to see no signs or symptoms. Less commonly, a low platelet count (signs may include bruising) and/or anemia (signs may include lethargy, weakness, and pale gums) may be seen. Frequent CBCs (complete blood counts) are done during chemotherapy to watch for these problems. If a low white blood cell count occurs, antibiotics may be prescribed, and the chemotherapy may be decreased or stopped. Rarely, the animal may be hospitalized for treatment. With most chemotherapy drugs, the bone marrow suppression is reversible.
Gastrointestinal upset: Usually seen as loss of appetite, weight loss, vomiting, and/or diarrhea. A bland diet, anti-vomiting and anti-diarrheal medications may be recommended, and chemotherapy may be decreased or stopped. If GI upset occurs, medications to prevent nausea and vomiting may be given before each future chemotherapy.
Allergic reactions: signs can range from itchiness and swelling of the face, stomach upset, and rapid breathing, to shock (anaphylaxis) Treatment may include antihistamines and anti-inflammatory medications, or treatment in the hospital for shock. Medications to prevent allergic reactions may be given before certain chemotherapy drugs to prevent allergic reactions.
Changes in hair coat: Most dogs and cats will not experience significant hair loss. Certain hair coat types (Schnauzers, Poodles, Old English Sheepdog) are most susceptible. Cats often lose their whiskers and acquire a softer coat. A dull hair coat, slow regrowth in shaved areas, and increased shedding may be seen with any chemotherapy drug, and usually improves after chemotherapy is stopped, or once maintenance chemotherapy is begun.
What should I do if I think my pet is experiencing side effects?
Before calling, take your pet's temperature at home (you may use a standard digital or glass thermometer; gently insert about 1 inch into the rectum). Normal body temperature for dogs and cats is about 100 - 101.5. Then give us a call.
A doctor or technician will review your pet's signs with you and make recommendations regarding at home care vs. reevaluation at our hospital.
Should I continue my pet's routine preventive care?
Please ask us about vaccinations as they come due -assessment is made on a case by case basis. Other preventative care such as flea and tick products and heartworm medications, should be continued unless otherwise instructed. Should your pet experience any minor health problems unrelated to the cancer or the chemotherapy, such as ear infections, skin problems. etc., you should consult your primary care veterinarian.