Chemotherapy is the use of certain chemical substances to treat disease. It is a treatment technique in its own right as well as surgery. The first known use of chemotherapy was in the use of the bark of quinoa by the Indians of Peru, in the treatment of fevers such as malaria.
Today, the term “chemotherapy” is mainly used to refer to treatments against cancer. Cancer is the uncontrolled growth of cells due to genetic mutations and, occasionally, a hereditary predisposition to develop certain tumors.
Most types of chemotherapy work by stopping mitosis (division of the cell nucleus), effectively targeting dividing cells too quickly. As these substances can damage cells, they are called “cytotoxic”. Some of these molecules cause a real “cell suicide” apoptosis.
Most chemotherapy agents used today are not the newer drugs, nor has a specific effect on neoplastic cells, so they also affect healthy cells.
This implies that other rapidly dividing cells, such as cells responsible for hair growth or regeneration of the intestinal epithelium, or blood cells, are also affected. This explains common side effects such as hair loss, decreased white blood cells, anemia (destruction of red blood cells) and bleeding (platelet destruction).
There has been significant progress in recent years with the advent of targeted therapies on the market. These consist of new molecules which are the majority of monoclonal antibodies that target a receiver or a specific part of the cancer cell. These molecules have revolutionized the treatment of certain cancers. The best examples are Herceptin in breast cancer that targets the HER-2 receptor and Gleevec in leukemia targeting the Philadelphia chromosome and the A-chromosome.