Types of Chemotherapy Drugs
Paul Ehrlich originated the term chemotherapy in 1914 while searching for a substance to cure syphilis. Although many agents have been developed to treat infectious diseases induced by bacteria, the development of anti-cancer agents has been by trial and error, serendipity or empiricism. These agents are classified according to their composite structure, similarity to other compounds, derivation, and mechanism of intracellular action. Engineered anti-cancer agents (designer drugs) such as monoclonal antibodies, cytokines, gene therapy vectors, antisense and peptide molecules have only been developed recently. Specific therapies are dependent on metabolic functions, which differ from normal cells, and are unique to the malignant cell. Fundamental experimental observations support the concept that chemotherapeutic agents primarily function by inhibiting mitosis (cell reproduction) and inducing apoptosis (cell death).
We organize chemotherapy drugs by category
Chemotherapy is employed in caring for half the patients who develop cancer. Most chemotherapy drugs kill cancer cells outright, or stop their reproduction and spread by inhibiting metabolic functions of the cancer cell. These drugs are called “cytotoxic.” The can also act on healthy cells (because they also divide) which is the basis for side effects and unwanted complications of therapy.
Some chemotherapy agents work in specific parts of the cell’s reproductive cycle. You see agents that are described as inhibiting the S-Phase or the M-Phase. Others are non-phase specific.
Other drugs do not fall into the “cytotoxic” category, but instead work by disrupting the ability of the tumor to stay intact. This is the method of action that most targeted therapies use.
Chemotherapy is an individual treatment plan designed specifically for each patient in which a drug or group of drugs is administered by oral or intravenous route (or other less commonly used routes such as intrathecal injection) at a precise dose, based on weight, and given over a finite and defined time period. Adjuvant therapy is chemotherapy given to high risk patients after other definitive local therapy (radiation or surgery) has removed the tumor. It is established therapy for breast, colorectal, osteosarcoma, Wilm’s tumor and some stages of gastric, non-small lung cell cancers and some melanomas. On the other hand, non-adjuvant therapy is given as primary chemotherapy before other localized therapy such as surgery or radiation is used. It may be beneficial in treatment of advanced but limited breast tumors, laryngeal, esophageal, bladder, anal cancers and some sarcomas.