Cancer Care Clinic: Chemotherapy FAQ
WHAT IS CHEMOTHERAPY?
Cancer cells multiply rapidly, resulting in tumor growth and potentially metastasis (spread to other organs). Chemotherapy drugs (chemo) are compounds that kill fast-growing cancer cells. They may be administered intravenously (IV), by subcutaneous (under the skin) or intramuscular (IM) injection, or orally. Traditional chemotherapy drugs work by damaging cellular processes so that cancer cells cannot grow and divide, eventually killing them. Not all drugs work for all cancers, and in some cases, a combination of drugs is the best course of treatment.
WHAT ARE THE BENEFITS OF CHEMOTHERAPY?
The benefits of chemotherapy differ by the type of cancer and treatment. General goals of chemotherapy can include: cancer cure, cancer remission, decrease risk of local recurrence, decrease risk of metastasis (spread of cancer), shrink or stabilize a tumor, improve survival, or preserve a good quality of life. Chemotherapy is very effective as the only treatment for some types of cancer. For other cancers it may be recommended after surgical removal of a mass to minimize the growth of metastasis in other organs. Occasionally, chemotherapy may be used in conjunction with radiation to help increase the ability of the radiation to kill the cancer cells.
ARE THERE RISKS OR SIDE-EFFECTS INVOLVED?
In general, chemotherapy is EXTREMELY well tolerated in dogs and cats, with minimal side effects.
There are some risks involved with any type of treatment for cancer. Most chemotherapy drugs cannot differentiate between fast-growing cancer cells and other normal cells in our body that grow quickly. Normal cell damage may result in side effects in some pets. Usually these side effects are manageable and are outweighed by the benefits of killing cancer cells. In one study, 95% of veterinary oncology clients had a positive experience and felt the treatment was effective for their pet.
Dogs and cats generally tolerate chemotherapy much better than human patients. The two side effects encountered most commonly are irritation to the gastrointestinal tract and bone marrow suppression. Normal cells in both sites divide very rapidly, so they maybe more susceptible to the toxic effects of the chemotherapy. Gastrointestinal signs may include decreased appetite, nausea, vomiting, and/or diarrhea. Symptoms are usually mild and can be resolve quickly with supportive care at home. Less than 5% of veterinary patients require in-hospital care for side effects of chemotherapy.
If the cells of the bone marrow are affected, the result may be more serious. If these progenitor cells which produce the white blood cells are damaged, the patient's white blood cell count may drop low enough to result in an increased susceptibility to infection. White blood cell counts of all chemotherapy patients are monitored carefully and antibiotics are used preventatively when needed. In rare cases (~1-2 out of every 100), a pet may need to be hospitalized to treat a blood infection.
Hair loss in pets receiving chemotherapy is usually very minor, although some breeds are prone to significant hair loss (e.g. poodle, Old English sheepdog, schnauzer, Lhasa apso, Shih Tzu, or Maltese). Animals such as Scottish terriers often lose their beards. Hair will grow back after completion of chemotherapy. Cats will lose their outer haircoat, leaving their soft undercoat, and will also lose their whiskers.
Some chemotherapy drugs can be extremely irritating to tissues if leakage occurs during injection, which can cause severe inflammation, ulceration, and swelling at the injection site. This complication is rare because drugs are administered carefully through catheters by experienced technicians and doctors. Other potential side effects are drug-specific, with damage to the kidneys or liver being possible with some drugs. Such side effects are monitored for and treatment is adjusted if problems are noted.
HOW WILL WE KNOW IF THE CHEMOTHERAPY IS WORKING?
Monitoring for response to chemotherapy will include physical examinations as well as diagnostic tests such as blood work or imaging (e.g. radiographs or ultrasound). Recommendations for specific tests will depend on the tumor type, organs involved, and chemotherapy protocol. Your doctor and the chemotherapy veterinary technician will keep you updated on your pet's response at each visit and will outline the plan for the next visit.
IS CHEMOTHERAPY EXPENSIVE?The exact cost of chemotherapy depends on the size of the patient, number of treatments, and the drugs being administered. Several treatment options may be available to fit financial as well as time constraints. The projected cost of your pet's specific treatments will be discussed in detail with you. This estimate will include medication cost, administration fees, doctor examinations and routine blood work monitoring. Financing is available through Care Credit.
HOW IS CHEMOTHERAPY GIVEN?The type, dose, schedule and duration of your pet's chemotherapy protocol are determined by your oncology doctor. Administration of chemotherapy is performed by our Cancer Care Clinic staff, comprised of trained veterinary technicians and doctors. Almost all cases are outpatient treatments. Chemotherapy administration is not painful; during treatment, we make every effort to keep your pet comfortable and stress-free.
HOW OFTEN AND FOR HOW LONG WILL MY PET RECEIVE CHEMOTHERAPY?
The length of a particular chemotherapy protocol will vary depending on the disease being treated. Drugs are commonly given in the hospital once every week to once every three or four weeks, depending on the type of cancer and treatment. Some oral drugs are prescribed for home use.
WHAT ABOUT DIET AND OTHER MEDICATIONS WHILE RECEIVING CHEMOTHERAPY?
Tell your doctor about all over-the-counter and prescription medications, including vitamin or herbal supplements. Give your doctor a list including the drug name and dosage. Some medicines may interfere with chemotherapy. Your doctor will give further instructions on medication use. Discuss your pet's current diet with your doctor and do not make any changes without consulting your doctor. If your pet has mild gastrointestinal upset from chemotherapy, your doctor will often make specific recommendations for a bland diet that may include prescription pet food or home-cooked food.