The Perseus Foundation

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🐾 Onco Bits of Knowledge 🐾 Chemotherapy is a word that creates an instant emotional response in everyone. Visions of debilitating nausea, hair loss, and lack of energy appear at the thought of having to receive chemotherapy. However, the reality of chemotherapy for animals is much different from that of human cancer patients. What to Expect if my Pet Needs Chemotherapy During your first visit, your veterinary oncologist will go over your pet’s personalized chemotherapy plan in detail. A member of the team will also describe next steps and the process around scheduling subsequent chemotherapy treatments for your dog or cat. Please don’t hesitate to reach out to your veterinary oncology team if anything remains unclear after your visit. At subsequent chemotherapy appointments: A technician will ask follow up questions related to how your pet has been doing. These may include any symptoms or signs that developed over the last week, observations about the energy level of your pet, changes in behavior, and whether prescription refills are needed. He or she will also ask about how treatment is going in reference to the ongoing quality of life for both you and your pet. A team member will draw a blood sample for a CBC (Complete Blood Count). This blood test is required before administration of chemotherapy to ensure that the white blood cells are adequate for treatment. If your pet requires an intravenous drug, an IV catheter will be placed in a leg to administer the treatment. Rarely, light sedation may be required in order to keep your pet still during treatment. Frequently Asked Chemotherapy Questions WHAT IS CHEMOTHERAPY? The use of a drug or chemical to treat any illness is considered “chemotherapy”, but this term commonly refers to the use of drugs in the systemic treatment of cancer. The ultimate goal of chemotherapy would be to cure the patient of cancer. In most instances at this point in time in veterinary medicine, this goal is not realistic. The goals the team strives to control rapidly progressive disease, prevent spread of the tumor, restore deteriorated function, and provide a good quality of life during the time of remission. The term “remission” refers to the time interval during which there are no outward signs that the patient has cancer. Unfortunately, it is impossible to predict in many cases which animals will achieve a full remission or for how long. Every situation and client-pet situation is different and must be dealt with individually. In appropriate situations, chemotherapy can be used to benefit pets with cancer. Most pets tolerate chemotherapy well, do not realize that they are ill, and appear to enjoy their extended life. However, each owner must believe that they are doing the right thing for their pet, in their situation. If it becomes obvious that therapy is not working, or that the pet is experiencing pain or discomfort, your team will discuss and make recommendations for changes in the treatment plan. HOW DOES CHEMOTHERAPY WORK? Cancer cells generally multiply very rapidly. Most chemotherapy drugs work by damaging rapidly growing cells (including both cancer cells and some normal cells in the body). Different drugs interfere with different steps in the process of cell growth and division, but this action decreases the ability of these rapidly growing cells to divide, and kills them. Some newer targeted chemotherapy protocols attack specific cancer cells more specifically. Often, the best approach is to combine a series of different drugs in order to effectively kill the cancer cells. Your pet’s dose, schedule and treatment protocol will be customized for your pet’s type of cancer, and amended as needed throughout the course of care. A TYPICAL CHEMOTHERAPY APPOINTMENT During the first appointment, the doctor will examine your pet, and consult in detail with you and your regular veterinarian. Your oncologist will determine whether chemotherapy will be useful for your pet’s cancer. If the decision is made to move forward with chemotherapy, the doctor will discuss options, next steps and tailor the plan for chemotherapy for your dog or cat. Treatments are individually tailored, although specific chemotherapy protocols consisting of several different drugs are followed for different types of cancer. Many chemotherapy drugs are given intravenously through an IV catheter; others are administered as injections under the skin or orally. Before administering the chemotherapy to your pet, a blood sample is drawn. The white blood cell count, red blood cell count, and platelet count are checked to make sure that it is safe to proceed with treatment; in some cases, your pet may not receive treatment due to a low white or red blood cell count. Chemotherapy may take up to 1.5 hours to administer. In some rare cases, a patient may need to be sedated in order to keep them calm. If your pet requires an intravenous drug, an IV catheter will be placed in a leg to administer the treatment. The route chosen depends on the kind of cancer being treated and how well the therapy is tolerated by the patient. Treatments may be necessary on a daily, weekly, or monthly schedule. The specific length of your pet’s individual course of treatment will be discussed in detail with you. WILL MY PET EXPERIENCE SIDE EFFECTS? Maybe. Chemotherapy is a word that creates an instant emotional response in everyone. Visions of debilitating nausea, hair loss, and lack of energy appear at the thought of having to receive chemotherapy. However, the reality of chemotherapy for animals is much different from that of human cancer patients. Your team understands this no that the primary concern for pets receiving chemotherapy is quality of life. Doses of drugs and treatment schedules are designed to minimize discomfort to the patient, while providing the most effective defense against the disease. As a result, most people are pleasantly surprised at how well their pets feel while undergoing chemotherapy. Ideally, the dog or cat receiving chemotherapy does not even realize that he or she is ill, and most of our patients do not have side effects with treatment. The drugs used in chemotherapy, however, are extremely potent and side effects can occur in about 20-30% of animals that receive treatment. The potential for side effects must be balanced against the benefits of the chemotherapy and the side effects of the cancer if left untreated. Choosing chemotherapy for your pet is an individual decision The most common side effect reported by owners is that the pet seems to be “off” for a day or two. This might mean that the pet has slightly less energy or seems less excited than normal about eating. Less commonly, the pet may skip a meal or two, have one episode of vomiting or diarrhea, or seem lethargic. Unfortunately, there is no way to predict which pets will develop the most serious reactions. The animal receiving chemotherapy needs to be watched closely and taken to his or her veterinarian at the first sign of illness. Although serious side effects can occur with any chemotherapy, there is less than a 5% chance that a patient will be hospitalized with side effects. WHAT ARE THE POSSIBLE SIDE EFFECTS OF CHEMOTHERAPY IN PETS Practically all anti-cancer drugs have side effects. These side effects arise because the normal cells in the body are also exposed to the anticancer drug. The most sensitive normal cells are found in the blood, gastrointestinal tract, skin, and reproductive system. Consequently, potential side effects include infections, bleeding, decreased appetite, vomiting, diarrhea, thin hair coat or skin color changes, and sterility. Rare side effects associated with specific drugs include bladder discomfort, kidney damage, and heart failure. Although serious adverse effects can occur with any chemotherapy, there is less than a 5% chance that a patient will be hospitalized with side effects and less than a 1% chance of fatality caused by overwhelming infections. In general the potential benefit of treatment with anticancer drugs outweighs the possible side effects. Below are listed some of the potential side effects of many chemotherapeutic agents in more detail: Nausea (and refusal to eat) can occur in veterinary patients, and seems to occur more frequently in cats than in dogs. If this happens, it usually occurs 2-5 days after treatment, and it is usually transient requiring no specific treatment. Tempting the pet with favorite foods, and warming the foods slightly will often increase palatability. If this condition persists, medication to reduce nausea and promote appetite can be used. Vomiting can also occur during treatment, also typically 2-5 days after a treatment has been given. If your pet vomits once or twice, and otherwise seems bright, active, and alert, withhold food and water for 12 hours and then reintroduce water. If your pet does not vomit after drinking water, you can offer food. If the vomiting is repetitive (more than 3-4 times) or contains blood, if vomiting resumes with feeding, or if your pet is lethargic, weak, or depressed, your pet probably requires veterinary attention. Diarrhea may occur, but is often mild and transient. If stools are soft, feed bland food (boiled chicken and rice) for dogs. If the diarrhea is bloody, watery, persists for more than 24 hours, or if your pet is lethargic and has diarrhea, veterinary attention is required. Hair Loss (Alopecia): Pets rarely lose their hair, but if they do, they are not bothered by it as much as people are. Dogs and cats with fur vs. dogs with hair: Fur does not grow continually throughout their lives like it does in people. Therefore, hair loss in pets is rare. Exceptions include certain breeds of dogs, such as poodles, Old English Sheepdogs and other breeds with hair that grows continually and who require hair cuts to manage length. In general, if a pet needs to visit a groomer periodically to be clipped, then the pet may experience some degree of hair loss as a result of chemotherapy. Cats may, lose all or most of their whiskers. Reduction in the Number of White Blood Cells (Neutropenia): There are various types of cells in the blood. The decrease in the number of infection fighting white blood cells is known as neutropenia. Many chemotherapeutic agents impair the body’s ability to produce these white blood cells. As a result, neutropenia may occur seven to ten days after chemotherapy. Neutropenia, alone, is not a danger to a patient. However a patient’s ability to fight off infection is impaired by neutropenia. Prior to each dose of chemotherapy, we perform a complete physical exam and a blood test called a complete blood count (CBC) to make sure it is ok to administer the next chemotherapy treatment. Should the patient have a significant reduction in the number of white blood cells, the doctor may want to delay chemotherapy treatment and/or prescribe antibiotics to protect against infection. Hematuria (bloody urine): One of the chemotherapy drugs that we use [Cytoxan (cyclophosphamide)] may occasionally cause hematuria (bloody urine) in dogs. If this occurs, you should discontinue the medication immediately and contact us for treatment. This side effect is specific to Cytoxan (cyclophosphamide). If bloody urine occurs and Cytoxan (cyclophosphamide) is not being used, contact us or your regular veterinarian for evaluation. Allergic Reactions: Allergic reactions to chemotherapeutic agents are rare and generally will not be something you have to treat at home. Should a patient have an allergic reaction, it usually develops upon administration and would be treated at the hospital. However signs to look for at home are a red muzzle/ears, scratching/pawing at the face, hives, and vomiting. Heart Damage: In rare cases, some chemotherapeutic agents, such as Adriamycin (doxorubicin), can irreversibly damage the heart muscle. The dose of these agents prescribed for most dogs is below the dose that usually causes heart disease, and less than 10% of patients develop heart disease as a result of chemotherapy. We may recommend a cardiology consultation prior to administering Adriamycin (doxorubicin) in dogs that have preexisting heart disease or that are at increased risk of heart disease (such as Dobermans, Boxers, and Great Danes) Fever/Sepsis: Virtually all chemotherapeutic drugs can temporarily suppress the body’s ability to fight infections. If the white blood cell count (neutrophils) drops too much then the pet runs the risk of developing a systemic infection. The pet will usually manifest a fever (but not always). If the bacteria travel through the bloodstream, it is known as sepsis. In rare cases, shock can occur (septic shock), and without rapid treatment, the risk of death is high. Though this period of susceptibility is brief, and occurs at a fairly predictable time, its consequences can be life threatening. Signs of fever or sepsis include: Fever greater than 103F: (temperature is taken by a re**al thermometer and should normally be between 99F and 102.8F). If you think your pet may have an infection, you may check your dog’s temperature re**ally at home (cats usually will not tolerate this). A digital thermometer is easiest to use; if it is 103 degrees or higher, please call us. If signs of an infection are noted, we will recommend that you bring your pet to the hospital for examination and treatment as soon as possible. This situation can be treated rapidly and almost always successfully. However, an extended delay before initiation of treatment may result in health complications or even death. We can see your pet at any time of the day or night if you suspect your pet has an infection. Extreme lethargy: Refusal to get up off pet bed, etc. Complete disinterest in food Extreme weakness Pale and somewhat sticky gums Severe vomiting and/or diarrhea WILL MY PET BE SICK THE DAY OF TREATMENT? Immediate reactions to chemotherapy are rare and occur shortly after treatment; we monitor patients carefully after treatment for these reactions prior to sending them home. In general, chemotherapy patients do not feel ill the day of therapy and should be able to participate in all normal activities on the day of treatment. We want your pet to have a great quality of life during therapy and enjoy all of their favorite activities as much as possible. CHEMOTHERAPY PRECAUTIONS You and your pet can continue to have normal, unlimited contact with each other throughout the course of your pet’s chemotherapy treatment. However, the following safety precautions should be followed. In some cases these precautions are not necessary, but it’s best to establish a safe routine. When in doubt, it is always better to be overly cautious! Avoid physical contact with your pet’s urine and f***s while receiving chemotherapy for 48-72 hours after each treatment (depending on the drug administered). You can wear gloves when picking up your dog’s stool or when cleaning your cat’s litterbox. Please double-bag the waste and throw it into the garbage. If your pet urinates or defecates in your home, wear gloves when you clean the area. You can use a regular household cleaner when cleaning the area. Always wear gloves when handling tablets of chemotherapy. Never split chemotherapy pills. Prednisone, antibiotics and drugs to prevent nausea/diarrhea can be handled safely without gloves. Store all pills safely out of the reach of children and pets. Pregnant or nursing women, people actively trying to conceive, immunosuppressed individuals, and children should avoid all contact with chemotherapy drugs and the waste from pets treated with chemotherapy. WHAT HAPPENS AFTER TREATMENT IS OVER? It is important for your veterinary oncologist or your regular veterinarian to examine your pet at consistent intervals after chemotherapy is over. This will allow potential problems, such as recurrence of the cancer, to be detected before they become too advanced. Finally, it is important for owners of pets who have had chemotherapy to realize that the cancers we treat are rarely cured. Almost all of our patients ultimately have recurrence of their cancers. However, it is vital to understand that most pets receiving chemotherapy have an excellent quality of life both during and after treatment. It is often possible to provide many additional months, or sometimes even years, of happy life following chemotherapy. The vast majority of owners tell us that they have no regrets about their decision to pursue chemotherapy for their pet.