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Chemotherapy (pronounced keem-o-therapy) is the use of certain drugs to treat disease, as distinct from other forms of treatment, such as surgery. Chemotherapy dates at least as far back as the use, by the Indians of Peru, of cinchona bark in the treatment of fevers, such as malaria. The first modern chemotheraputic agent was Paul Ehrlich's arsphenamine, an arsenic compound discovered in 1909 and used to treat syphilis. This was later followed by sulfonamides discovered by Domagk and penicillin G discovered by Alexander Fleming.Please note that today, the term chemotherapy is mostly used for the drug treatment of cancer, and the rest of this article discusses that topic. Antibiotics are referred to as antibacterial chemotherapy, but in medical practice this word is only used in the context of the treatment of tuberculosisTuberculosis is also called TB consumption (TB seemed to consume people from within with its symptoms of bloody cough, fever, pallor, and long relentless wasting), wasting disease White Plague (TB sufferers appeared markedly pale), phthisis (Greek for con.
Other uses of chemotherapy agents (including the ones mentioned below) are the treatment of autoimmune disease ( DMARDs).
1 Chemotherapy for cancer
Cancer is the uncontrolled growth of cellstained for keratin The cell is the structural and functional unit of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, (humans have an estimated 100,0s due to damage to DNADeoxyribonucleic acid DNA is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses. DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate ( mutationThis article is about mutation in biology, for other meanings see: mutation (disambiguation). Mutations are permanent, transmissible changes to the genetic material (usually DNA or RNA) of a cell. Mutations can be caused by copying errors in the genetic ms) and, occasionally, due to an inheritedA genetic disorder or genetic disease is a disease caused, at least in part, by the genes of the person with the disease. There are a number of possible causes for genetic defects: They may be caused by an unwelcome mutation, as are most cancers. There ar propensity to develop certain tumours.
Broadly, most chemotherapeutic drugs work by impairing mitosisIn biology, mitosis is the process of chromosome segregation and nuclear division that follows replication of the genetic material in eukaryotic cells. This process assures that each daughter nucleus receives a complete copy of the organism's genome. ( cell division), effectively targeting fast-dividing cells. As these drugs cause damage to cells they are termed cytotoxic. Some drugs cause cells to commit apoptosis (effectively "cell suicide").
Unfortunately, scientists have yet to be able to locate specific features of malignant cells that would make them uniquely targetable (barring some recent examples, such as the Philadelphia chromosome as targeted by imatinib). This means that other fast dividing cells such those responsible for hair growth and replacement of epithelium in the intestine are also affected. However, some drugs have a better side-effect profile than others, enabling doctors to adjust treatment regimens to the advantage of patients in certain situations.
As chemotherapy affects cell division, tumours with a high growth fractions (such as acute myelogenous leukemia and the lymphomas, including Hodgkin's disease) are more sensitive to chemotherapy, as a larger proportion of the tumour cells are undergoing cell division at any time.
Chemotheraputic drugs affect "younger" tumours (i.e. less differentiated) more effectively, because at a higher grade of differentiation, the propensity to growth decreases. In some solid tumours, cell division has effectively ceased, making them insensitive to chemotherapy. Another problem with solid tumour s is the fact that the chemotherapeutic agent often does not reach the core of the tumour. Solutions to this problem include brachytherapy and, of course, surgery.
