In dogs and cats, we generally do not expect the same severity of side effects as are often seen in humans, since veterinary oncologists usually use lower doses of chemotherapy than those used in man. We also do not generally combine drugs together to be administered in rapid succession, as is done in humans. These precautions taken in our pets prevent many of the severe side effects commonly experienced by people taking anticancer drugs. Since chemotherapeutic drugs travel throughout the body, they can seek out tiny numbers of tumor cells which are not visible by any currently available diagnostic test, whereas surgery and conventional radiation therapy can only treat one particular area of the body. Anticancer drugs may also be administered when there remains a very great likelihood that there are still microscopic tumor cells in other parts of the body after a tumor has been removed surgically or treated with radiation therapy, This form of drug treatment is called adjuvant chemotherapy , because it is used to increase the number of cures achieved with surgery or radiation therapy alone.
Adjuvant chemotherapy is used similarly, in hopes of increasing the cure rate in cancer treatment.
Of course, these effects that work to kill tumor cells also cause changes in normal cells, with resultant deleterious side effects in the patient being treated. This is often very difficult to do, and a slight amount of nausea is common for a few days, especially at the beginning of chemotherapy. This period is called induction , and higher doses and more types of drugs may be used during this phase. The goal of induction chemotherapy is to bring the patient into remission , which is defined as tumor shrinkage until no visible tumor nodules or masses remain. After induction, some tumors may not be in remission but may have shrunk to the point that surgery can remove the rest of the tumor.