Is Chemotherapy Right for Your Pet?

By Jennifer Coates, DVM on Nov. 4, 2013

In the past, a diagnosis of cancer in a pet typically resulted in two treatment options: euthanasia now or euthanasia later (hopefully with the pet receiving comfort care in the meantime). Nowadays, owners have many more options.

Surgery is the first line of treatment for cancerous masses that have not obviously metastasized. Complete surgical removal can sometimes be curative, but even when that is not possible, removing the bulk of the cancer will often greatly improve patient comfort and the length of his or her remission.

Radiation therapy can be used to shrink a cancerous tumor before surgery, to treat “dirty margins” (areas around the surgical site where cancerous cells remain), to improve patient comfort, or as the primary form of treatment for some types of cancers.

Chemotherapy is a part of most cancer treatment protocols, particularly when the cancer is known or suspected to have metastasized or is of a type that affects multiple parts of the body at the same time (e.g., lymphoma or leukemia).

Some owners elect not to pursue surgery, radiation therapy, or chemotherapy for their pet’s cancer. Oftentimes, they have very good reasons for not doing so. Concurrent disease, the stress of treatment, extremely advanced age, and (unfortunately) finances all have to be taken into consideration when deciding what treatment options are appropriate for pets and their owners. What should never play a role, however, is a misunderstanding regarding the likelihood of side effects from treatment. Chemotherapy has a particularly bad reputation in this regard.

Even though veterinarians and medical doctors use many of the same drugs when designing chemotherapy protocols for their patients, the incidence of side effects in dogs and cats is MUCH lower. This doesn’t have anything to do with the inherent toughness of dogs and cats; it simply results from the fact that veterinarians take a different approach in comparison to medical doctors.

People understand the concepts of delayed gratification and sacrifices in the short term bringing about gains in the long term. I have great regard for the mental capacities of (some) dogs and cats, but frankly, I think these concepts are beyond them. For this reason, veterinarians are not willing to significantly compromise a pet’s current well-being for a “cure” that may or may not happen. We tailor our chemotherapies in such a way that the nausea, anemia, hair loss, and exhaustion that are part and parcel of human chemotherapy protocols are the exception rather than the rule for dogs and cats. The majority of my patients who have been treated with chemotherapy for cancer don’t react poorly to the medications at all or only experience minor side effects.

But chemotherapy is still not for everyone. The flip side of taking a less aggressive approach is that cure rates and remission lengths are generally lower than they are on the human side of things, and owners do have to accept the possibility that adverse reactions are still possible, even if they don’t occur as frequently as is generally expected.