Major Categories of Chemotherapy Agents

Alkylating agents were among the first anti-cancer drugs and are the most commonly used agents in chemotherapy today. Although alkylating agents may be used for most types of cancer, they are generally of greatest value in treating slow-growing cancers. Alkylating agents are not as effective on rapidly growing cells.

Antimetabolites mimic nutrients that the cell needs to grow, tricking the cell into consuming them, so it eventually starves to death.

Plant alkaloids are antitumor agents derived from plants. These drugs act specifically by blocking the ability of a cancer cell to divide and become two cells.

Antitumor antibiotics act by binding with DNA and preventing RNA (ribonucleic acid) synthesis, a key step in the creation of proteins, which are necessary for cell survival. They are not the same as antibiotics used to treat bacterial infections. Rather, these drugs cause the strands of genetic material that make up DNA to uncoil, thereby preventing the cell from reproducing.

Examples of the various classes of chemotherapeutic drugs are listed in the table below.

Alkylating Agents Antimetabolites Plant Alkaloids Antitumor Antibiotic
chlorambucil purine antagonists actinomycin D doxorubicin
cyclophosphamide pyrimidine antagonists docetaxel mitoxantrone
thiotepa folate antagonists mitomycin bleomycin

SEER Rx helps one identify what class each chemotherapy agent falls in. This information is needed when the physician changes one drug in a regimen to determine whether a patient has transitioned from first course of treatment to subsequent treatment. The registrar is not expected to memorize this information.

One of the most important decisions for the oncologist is prescribing the right amount of anti-cancer drugs. Although large doses will kill more cells, greater amounts of drugs will produce more severe side effects. However, lowering the dosage to minimize side effects will also reduce the chances of success. The usual practice is to use the maximum safe dose for effectiveness, even at the cost of temporary side effects.

Updated: December 21, 2023