cancer
Syringes are used to harvest bone marrow from the pelvis of a donor prior to transplantation into a patient with leukaemia. Bone marrow is rich in blood-forming and immune system cells. Donated bone marrow can be used to save the lives of patients whose own marrow cells have been destroyed by the chemotherapy and radiotherapy needed to eradicate their cancers.
Group of diseases characterized by abnormal proliferation of cells. Cancer (malignant) cells are usually degenerate, capable only of reproducing themselves (tumour formation). Malignant cells tend to spread from their site of origin by travelling through the bloodstream or lymphatic system (see metastasis). Cancer kills about 6 million people a year worldwide.
Causes
There are more than 100 types of cancer. Some, such as lung or bowel cancer, are common; others are rare. The likely causes remain unexplained. Triggering agents (
carcinogens) include chemicals such as those found in cigarette smoke, other forms of smoke, asbestos dust, vehicle exhaust fumes, and many industrial chemicals. Some viruses can also trigger the cancerous growth of cells (see
oncogene), as can X-rays and radioactivity. Dietary factors are important in some cancers; for example, lack of fibre in the diet may predispose people to bowel cancer and a diet high in animal fats and low in fresh vegetables and fruit can increase the risk of breast cancer. Psychological
stress may also increase the risk of cancer, more so if the person concerned is not able to control the source of the stress.
Cancer genes
In some families there is a genetic tendency towards a particular type of cancer. In 1993 researchers isolated the first gene that predisposes individuals to cancer. About 1 in 200 people in the West carry the gene. If the gene mutates, those with the altered gene have a 70% chance of developing colon cancer, and female carriers have a 50% chance of developing cancer of the uterus.
| A report published in June 2001 in the Journal of the National Cancer Institute confirmed a decrease in the number of US cases and deaths from the major cancers. The number of new cases and deaths fell 1.1% each year from 1992 to 1998. Cancer deaths overall dropped by 2% for black men, who have historically had the highest death rates from the disease in the USA. Death rates also declined for lung and prostate cancer in men, and colorectal cancer in men and women. However, although breast cancer deaths in women fell by 2.4% each year, the report found that new cases of breast cancer rose 1.2% each year during the same period. |
| Around 550,000 people died from cancer in the USA in 2000. |
| In 1994 a gene that triggers breast cancer was identified. A mutation in the gene BRCA1 was found to be responsible for almost half the cases of inherited breast cancer, and most cases of ovarian cancer. In 1995 a link between BRCA1 and non-inherited breast cancer was discovered. Women with the mutated gene have an 85% chance of developing breast or ovarian cancer during their lifetime. A second breast cancer gene BRCA2 was identified later in 1995. |
| The commonest cancer in young men is testicular cancer, the incidence of which has been rising by 3% a year since 1974 (1998). In 2000 British researchers announced the discovery of a mutant gene that increases incidence of testicular cancer 50-fold. The gene TGCT1 is inherited from the mother and if a successful screening system is devised 95% of testicular cancer cases will be able to be predicted. |
Treatment Cancer is one of the leading causes of death in the industrialized world, yet it is by no means incurable, particularly in the case of certain tumours, including Hodgkin's disease, acute leukaemia, and testicular cancer. Cures are sometimes achieved with specialized treatments, such as surgery, chemotherapy with cytotoxic drugs, and irradiation, or a combination of all three. Monoclonal antibodies have been used therapeutically against some cancers, with limited success. There is also hope of combining a monoclonal antibody with a drug that will kill the cancer cell to produce a highly specific magic bullet drug. In 1990 it was discovered that the presence in some patients of a particular protein, p-glycoprotein, actively protects the cancer cells from drugs intended to destroy them. If this action can be blocked, the cancer should become far easier to treat. Public health programmes are concerned with prevention and early detection. |
Cancer
Faintest of the zodiacal constellations (its brightest stars are fourth magnitude). It lies in the northern hemisphere between Leo and Gemini, and is represented as a crab. The Sun passes through the constellation during late July and early August. In astrology, the dates for Cancer are between about 22 June and 22 July (see precession).
Cancer's most distinctive feature is the open star cluster Praesepe, popularly known as the Beehive, visible to the naked eye as a nebulous patch.
| In Chaldaean and Platonist philosophy Cancer was the ‘Gate of Men’, through which souls descended into human bodies, eventually returning to heaven through Capricornus, the ‘Gate of the Gods’. |
| In astrology, Cancer was one of the unfortunate signs governing the human breast and stomach. The object at the head of the Crab which Bayer called Epsilon Cancri is Praesepe. |
)
