Chemotherapy by Infusion for Malignant Bone Tumors

Abstract

One of the important factors for determining the destruction of human cancer cells by chemotherapeutic agents is the proliferative state of the tumor cell population at the time of drug exposure. Two classes of chemotherapeutic agents are available: one is nonspecific or cell-cycle specific; the second is phase specific (Valeriote and Von Pulten, 1975). Phase-specific agents kill cells in one phase of the cell cycle and have little effect on cells in other phases, whereas cell cycle specific agents kill cells throughout the cell cycle and are less cytotoxic to cells in the nonproliferative state. These differences in cell··cycle kinetics are responsible for the differences in tumor response to various anticancer agents. For example, little or no response would be noted with a cell cycle specific drug in a tumor with a large fraction of cells in the resting or G₀ phase (low grade or mitotically inactive tumors). If the drug were administered frequently, however, or if the exposure were prolonged, then more normal hemopoietic stem cells would be destroyed, causing increasing toxicity and intolerable side effects to nonmalignant cells that would be mitotically active.