Pet Chemotherapy: the Good, the Bad and the Ugly

Cancer…maybe one of the scariest words a person can hear from a trusted veterinarian in reference to a pet, or should I say a beloved member of the family. But let’s face it, our furry friends live longer and better lives thanks to improved veterinary care, quality diets and better-educated owners as their pets age well and with longer lives, animals have a greater chance of reaching ages where cancer becomes common, affecting 1 in 4 dogs and 1 in 5 cats during their lifetime.

But, cancer is not as scary as it used to be. Advances in both human and veterinary medicine have resulted in many cancers being beatable or at least controllable, allowing many more years of happy, good-quality life. Some of the most important advances have been in the area of chemotherapeutics and in the proper application of chemotherapy for different types of cancer.

The first thoughts that often come to mind when someone hears “chemotherapy” are of very dangerous chemicals that bring patients to the brink of death and such severe side effects that death would seem like a blessing. But this is not the case in veterinary medicine. By applying the most current knowledge, the risk of severe side effects has been reduced to less than 5% of patients undergoing chemotherapy, with most patients enjoying a good quality of life while being treated.

Those that do experience severe side effects include bone marrow suppression, gastrointestinal upset, and less commonly alopecia (hair loss). Most chemotherapeutics target rapidly dividing cells in the body and unfortunately this does not limit their effects to just cancer cells. Bone marrow tissue is one of the most rapidly dividing tissues in the body, making it an innocent bystander in the war on cancer. When bone marrow cells are destroyed, this can leave the body’s immune system suppressed and the body more susceptible to infections that would not normally be a problem. Routine periodic bloodwork can watch for decreased numbers of white blood cells and help avoid problems by making necessary adjustments in an individual patient’s chemotherapy protocol. Gastrointestinal side effects are not common but may result from the effect of chemotherapy drugs on the vomiting centers in the brain or from direct damage and inflammation of the stomach and intestinal tract. These side effects are most often treated symptomatically until adjustments can be made to alleviate them. Alopecia is rare for veterinary patients because most animals do not have continuously growing hair, although some non-shedding breeds may be affected.

Close monitoring and anticipating possible side effects can result in safe, effective use of chemotherapy to help patients reach a state of remission and give people valuable time to spend with their furry companions.