Chemotherapy for Dogs and Cats: Understanding the Treatment Experience
When a beloved animal is given a diagnosis of cancer, the effect on the animal’s family can be devastating, marked by confusion and sadness. It is important to understand the treatments that are available for an animal’s cancer. The veterinarian may recommend chemotherapy, either alone or in combination with other treatments, as part of your pet’s cancer management. The thought of chemotherapy strikes fear in the hearts of animal owners, based on the human experience of undergoing chemotherapy. Everyone’s lives are touched by cancer in some way, and yet an animal’s experience will be different from a human’s experience, in several ways.
“While the chemotherapy drugs used for both human and pet cancers are the same, the treatment experience is often drastically different,” explains Kimberly Reeds, DVM, MS, DACVIM (Oncology), of Holland’s Veterinary Referral Hospital in Oklahoma City. “In humans, the goal of cancer treatment is to cure. While many patients experience long survival times, they also experience severe treatment side effects.”
“Unfortunately, cancer is rarely cured in pets,” adds Dr. Reeds, “and the goal of cancer treatment is to provide relief from cancer symptoms, while also providing an acceptable quality of life for as long as possible.”
The Administration of Chemotherapy in Animals
The chemotherapy drugs used to treat an animal may come in either an injection or pill form. Your veterinarian will review the administration procedures relative to your pet’s protocol and will also inform you if any other procedures such as placement of a vascular access port (VAP) or the use of sedation is required.
Pills may be administered at the veterinary clinic or they may be sent with you to be administered at home. The veterinarian will instruct you how to properly handle and administer these drugs.
Chemotherapy injections will only be administered at the veterinary clinic. Most often, these injections are given as an intravascular (IV) injection but they may also be given under the skin (subcutaneous or SQ), into the tumor, or into a body cavity such as the chest or abdomen.
The Side Effects of Animal Chemotherapy
Each chemotherapy drug will typically have a specific side effect. After each treatment, the veterinarian will outline the clinical signs for you to monitor and advise you as to when to seek medical assistance.
Pets, in general, will experience fewer and less severe side effects than humans. This is due to the lower doses and less intense dosing schedules used in pets. With any chemotherapy drug, however, three main side effects can be expected:
Bone marrow suppression
Bone marrow suppression is a frequent side effect of chemotherapy, the severity of which depends on the drug administered. The main risk to the patient is the development of a systemic infection (sepsis) or a bleeding problem. The veterinarian will prescribe a specific schedule of blood work (most often a complete blood count or CBC) to be performed to monitor when the cell counts should be at their lowest, so that problems may be addressed if needed. Blood work will also be performed prior to each treatment.
While undergoing chemotherapy, pets may exhibit vomiting, diarrhea or a decreased appetite. Most patients will experience these side effects three to five days after chemotherapy has been administered; however, some drugs cause these signs immediately. In the majority of the patients, these problems will resolve on their own with no medical intervention. Veterinary care should be sought for patients that have severe vomiting or diarrhea, and for those that have stopped drinking to treat any dehydration.
Hair loss is not commonly encountered in pets undergoing chemotherapy. The reason is that animals do not have the continually growing hair that humans do. Dog breeds that are susceptible to hair loss include, but are not limited to the Old English Sheepdog, poodles and the Bichon Frise. Many patients may lose whiskers or guard hairs. Shaved hair will return more slowly than normal. Know that these are cosmetic changes and are not harmful to your pet.
If you have concerns about your dog or cat, and you need to locate a board-certified internal medicine veterinarian with an oncology specialty, use the VetSpecialists.com search tool on the website’s homepage. The tool allows you to search for a veterinary oncologist then select the type of animal along with your location by zip code or city name. Contact the hospital of your choice to discuss your pets’ signs and to review whether there is a need for a referral from your primary care veterinarian.