Chemotherapy

Chemotherapy is the use of chemical substances to treat disease. In its modern-day use, it refers almost exclusively to cytostatic drugs used to treat cancer.

Principles

Cancer is the uncontrolled growth of cells due to damage to DNA (mutations) and, occasionally, due to an inherited propensity to develop certain tumours. Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body - in other words, the body attacks its own cells. In a contrast, transplant rejection happens because a normal healthy human immune system can distinguish foreign tissues and attempts to destroy them. Also the reverse situation, called graft-versus-host disease, may take place.

Related Topics:
Cancer - Cell - DNA - Mutation - Inherited - Tumours - Autoimmune diseases - Transplant rejection - Graft-versus-host disease

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Broadly, most chemotherapeutic drugs work by impairing mitosis (cell division), effectively targeting fast-dividing cells. As these drugs cause damage to cells they are termed cytotoxic. Some drugs cause cells to undergo apoptosis (so-called "cell suicide").

Related Topics:
Mitosis - Cell division - Apoptosis

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Unfortunately, scientists have yet to be able to locate specific features of malignant and immune 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 for replacement of the intestinal epithelium (lining) 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.

Related Topics:
Philadelphia chromosome - Imatinib - Hair - Intestinal - Epithelium - Side-effect - Doctors

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As chemotherapy affects cell division, tumours with 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 targeted cells are undergoing cell division at any time.

Related Topics:
Acute myelogenous leukemia - Lymphoma - Hodgkin's disease - Cell division

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Chemotherapeutic drugs affect "younger" tumours (i.e. less differentiated) more effectively, because at a higher grade of differentiation, the propensity to growth usually decreases. Near the center of some solid tumours, cell division has effectively ceased, making them insensitive to chemotherapy. Another problem with solid tumours is the fact that the chemotherapeutic agent often does not reach the core of the tumour. Solutions to this problem include radiation therapy (both brachytherapy and teletherapy) and surgery.

Related Topics:
Radiation therapy - Brachytherapy - Teletherapy - Surgery

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