Carcinogenesis Health Dictionary

When a new drug is introduced, it has usually been studied only in relatively few patients – typically 1,500. If n patients have been studied, and no serious effects observed, there is still a chance of a serious adverse e?ect occurring in the general population as frequently as 3/n (1:500).

Adverse effects can be divided into types. First, those which are closely related to the concentration of the drug and accord with what is known of its PHARMACOLOGY. These so-called type A (augmented pharmacological) effects are distinguished from type B (bizarre) effects which are unpredictable, usually rare, and often severe. ANAPHYLAXIS is the most obvious of these; other examples include bone-marrow suppression with CO-TRIMOXAZOLE; hepatic failure (see HEPATITIS) with SODIUM VALPROATE; and PULMONARY FIBROSIS with AMIODARONE. A more comprehensive classi?cation includes reactions type C (chronic effects), D (delayed effects – such as teratogenesis or carcinogenesis) and E (end-of-dose effects – withdrawal effects). Examples of adverse reactions include nausea, skin eruptions, jaundice, sleepiness and headaches.

While most reported adverse reactions are minor and require no treatment, patients should remind their doctors of any drug allergy or adverse e?ect they have suffered in the past. Medical warning bracelets are easily obtained. Doctors should report adverse effects to the authorities – in the case of Britain, to the Committee on Safety of Medicines (CSM), using the yellow-card reporting machinery.... adverse reactions to drugs

Invisible light rays of very short wavelength beyond the violet end of the sun’s spectrum. Ultraviolet-C (UVC) (wavelength <290 nm [nanometre – see APPENDIX 6: MEASUREMENTS IN MEDICINE]) is entirely absorbed by the earth’s atmosphere and would otherwise be lethally damaging. Ultraviolet-B (UVB – 290– 320 nm) intensity increases with altitude: it is greatest in midsummer and at midday and penetrates cirrhus cloud. UVB causes sunburn and also tanning. Ultraviolet-A (UVA – 320– 400 nm) penetrates deeper into our skins but does not cause sunburn; it is implicated in many photochemical reactions and PHOTODERMATOSES and in CARCINOGENESIS. UVR helps the skin to synthesise vitamin D.

Ultraviolet lamps produce UVR and are used to tan skin but, because of the risk of producing skin cancer (see SKIN, DISEASES OF), the lamps must be used with great caution.... ultraviolet rays (uvr)

A rare disease in which DNA repair mechanisms fail, rendering the skin especially vulnerable to damage from ultraviolet light (see ULTRAVIOLET RAYS (UVR)). Extreme photosensitivity begins in infancy; later, marked freckling occurs and premature CARCINOGENESIS in the skin usually leads to early death. There may also be neurological complications.... xeroderma pigmentosum

A unit of the material of heredity. A gene corresponds to a particular area of DNA within a chromosome. There are about 30,000 different genes arranged on the 23 pairs of chromosomes. These genes control the development and functioning of organs and body systems, providing an “instruction manual” for an individual’s growth, survival, reproduction, and possibly also for aging and death. Genes also play a part, together with environmental factors, in determining a person’s intelligence, personality, and behaviour.

Genes fulfil these functions by directing the manufacture of proteins. Many proteins have a structural or catalytic role in the body. Others switch genes “on” or “off”. The genes that make these regulatory proteins are called control genes. The activities of control genes determine the specialization of cells; within any cell some genes are active and others idle, according to its particular function. If the control genes are disrupted, cells lose their specialist abilities and multiply out of control; this is the probable mechanism by which cancers form (see carcinogenesis; oncogenes).Each of a person’s body cells contains an identical set of genes because all the cells are derived, by a process of division, from a single fertilized egg, and with each division the genes are copied to each offspring cell (see mitosis; meiosis). Occasionally, a fault occurs in the copying process, leading to a mutation. The gene at any particular location on a chromosome can exist in any of various forms, called alleles. If the effects of an allele mask those of the allele at the same location on its partner chromosome, it is called dominant. The masked allele is recessive. (See also genetic code; inheritance.)... gene

(carcino-) combining form denoting cancer or carcinoma. Example: carcinogenesis (development of).... carcin

n. any substance that, when exposed to living tissue, may cause the production of cancer. Known carcinogens include ionizing radiation and many chemicals, e.g. those found in cigarette smoke and those produced in certain industries. They cause damage to the DNA of cells that may persist if the cell divides before the damage is repaired. Damaged cells may subsequently develop into a *cancer (see also carcinogenesis). An inherent susceptibility to cancer may be necessary for a carcinogen to promote the development of cancer. See also oncogenic. —carcinogenic adj.... carcinogen

n. (in oncology) the first step in the development of cancer (see carcinogenesis).... initiation