When we make our patients sick: common side effects of chemotherapy

摘要

Theoretically, cancer chemotherapy is given to kill or suppress the growth of malignant cells without killing normal cells; in fact, however, most of the commonly-used drugs are capable of killing both normal and malignant cells, depending on the dose administered. To be useful in clinical practice, an antineoplastic drug must possess selective toxicity---in other words, it should be more toxic to cancer cells than to the normal host cells at conventional doses. Unfortunately, however, our patientssometimes become ill---sometimes unexpectedly---from doses of chemotherapy drugs that are usually well tolerated. This sequela of treatment is disturbing both to us as the veterinarian who administered the drugs and even more to the owner. This lecturewill define the side effects of drugs we commonly use in small animal cancer treatment and will outline measures we can use to prevent these toxicities and to remedy them if they occur. Cells of normal tissue are damaged by chemotherapy; most, given time, will recover. Tissues that are especially affected include those in which the cells have a short life span and require constant renewal, i.e., bone marrow, gastrointestinal mucosa, gonads, and hair follicles. Myelosuppression and subsequent infection are the most common dose-limiting toxic effects of chemotherapy. Drugs which seem to be particularly myelosuppressive in dogs and cats include cyclophosphamide, carboplatin, doxorubicin (particularly when used in combination with another chemotherapeuticagent), CCNU, BCNU, and vinblastine. In some cats, vincristine has been noted to produce a marked and prolonged neutropenia.