Receiving a diagnosis of cancer in a family member can be devastating; however, it is important to know that several treatment options may be available. Your veterinarian may recommend chemotherapy, either alone or in combination with other treatments, as part of your pet’s cancer management. While the chemotherapy drugs used for both human and pet cancers are the same, the treatment experience is often drastically different. In humans, the goal of cancer treatment is to cure and while many patients experience long survival times, they also experience severe treatment side effects. Unfortunately, cancer is rarely cured in pets 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.
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, three main side effects can be expected:
- Bone marrow suppression
This is a frequent side effect of chemotherapy, the severity of which depends on the drug administered. The main risk to the patient is development of a systemic infection (sepsis) or a bleeding problem. Your veterinarian will prescribe a specific schedule of blood work (most often a complete blood count or CBC) to be performed 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.
- Stomach upset
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 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, those that have stopped drinking or any time dehydration occurs.
- Hair loss
Hair loss is not commonly encountered in pets as they do not have the continual growing hair that humans do. Dog breeds that are susceptible include (but are not limited to) the Old English Sheepdog, poodles and the Bichon Frise. Many patients may lose whiskers or guard hairs and shaved hair will return more slowly than normal. These are cosmetic changes and not harmful to your pet.
In addition, each chemotherapy drug will have a specific side effect. After each treatment, your veterinarian will outline what clinical signs to monitor and when to seek medical assistance.
The drugs used to treat your pet may come in either an injection or pill form. Pills may be administered at the veterinary clinic or they may be sent with you to be administered at home. Your 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. 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.
Fact Sheet Author
Kimberly Reeds, DVM, MS, DACVIM (Oncology)
Oklahoma State University