/ kænsər /
Any malignant growth or tumor caused by abnormal and uncontrolled cell division; it may spread to other parts of the body through the lymphatic system or the blood stream.
Group of diseases characterized by abnormal proliferation of cells. Cancer (malignant) cells are usually degenerate, capable only of reproducing themselves (tumor formation). Malignant cells tend to spread from their site of origin by traveling through the bloodstream or lymphatic system (see metastasis).
There are more than 100 types of cancer. Some, like 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, exhaust fumes, and many industrial chemicals. Some viruses can also trigger the cancerous growth of cells (see oncogenes), as can X-rays and radioactivity. Dietary factors are important in some cancers; for example, lack of fiber in the diet may predispose people to bowel cancer and a diet high in animal fats and low in fresh vegetables and fruit increases the risk of breast cancer. Psychological stress may increase the risk of cancer, more so if the person concerned is not able to control the source of the stress.
In some families there is a genetic tendency toward 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.
This accounts for an estimated 10% of all colon cancer.
In Sept 1994 a gene that triggers breast cancer was identified. BRCA1 is responsible for almost half the cases of inherited breast cancer, and most cases of ovarian cancer. Women with the gene have an 85% chance of developing breast or ovarian cancer during their lifetime.
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 tumors, including Hodgkin's disease, acute leukemia, 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 programs are concerned with prevention and early detection.
A US trial commenced 1995 to treat cancer patients with gene therapy. Ten women with breast cancer were injected with a virus genetically engineered to destroy tumors. Up to 1 billion viruses were injected into the chest cavity over a four-day period. Researchers are hopeful of extending life expectancy, rather than providing a total cure.
UK trials began 1995 of a drug designed to check tumor growth and prevent cancer spreading. The drug, called BB-2516, performed well in animal trials.Its manufacturer hopes it will stabilize cancer in humans, enabling sufferers to lead relatively normal lives whilst maintaining dosage.