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Pet Health Information
Chemotherapy in Dogs and Cats
Chemotherapeutic drugs are used in veterinary medicine to treat a variety of different types of cancers. Many neoplasms are responsive to the drugs that we have available. Use of chemotherapy often provides our patients the best chance at prolonged survival.
How does chemotherapy work?
Chemotherapeutic drugs stop, or slow the replication of cells. Unfortunately, these drugs are not yet sophisticated enough to only target cancerous cells; other rapidly dividing cells in the body (such as the cells of the gastrointestinal tract and the cells or the bone marrow) are affected as well. It is when these "normal" cells are affected that we see side effects of the drugs.
What are the side effects?
Most common side effects include vomiting and diarrhea, due to destruction of the cells of the gastrointestinal tract. Often, this will be transient and resolve without medical attention. If the cells or the bone marrow are affected, the number of white blood cells usually drops. If this happens, your animal is more prone to obtaining secondary infections, such as respiratory or bladder infections. These infections will need to be treated with antibiotics. Occasionally, in about 5-10% of our chemotherapy patients, an infection becomes serious enough that your animal may need to be hospitalized for intravenous antibiotics and fluid support. If there are specific side effects to be expected from a drug used on your pet, we will provide you with that information on the day of treatment.
But I don’t want my animal to be sick from the chemotherapy.
Most of us have had experience with a person with cancer who received chemotherapy as a treatment. We are familiar with what human patients go through; nausea and vomiting, extreme lethargy and weakness, hair loss. In our animal patients, our goals are different. We don’t aim to cure the cancer, but to palliate our patients. This means that we aim to strike a balance between slowing the progression of the disease and giving our patients a good quality of life for their remaining time with us. The doses used in veterinary medicine are selected to meet this goal.
What do the treatments consist of?
Generally, the first couple months of treatment are very intensive and can be costly. Most drugs are given intravenously, and sometimes your pet will have to stay for the day to receive the drugs slowly. Sometimes there are oral medications to be given at home. You must be committed to this treatment course, which means getting your pet to the hospital for frequent treatments and evaluations. The drugs used, the duration of treatment, and the intensity of treatment are all dependent on the type of cancer your animal has, and how sick they are at the time of diagnosis. Generally, your pet receives 2 months of one protocol before decisions are made as to whether we need to change to other drugs or alter the schedule of treatment. Some animals will need to receive chemotherapy for the rest of their lives, whereas others who go into remission may have treatment discontinued.
If you have any other questions about what to expect from chemotherapy, please feel free to talk with one of our veterinarians.