The cells of most tissues are able to divide and reproduce exact of themselves. The process of normal cell division is under strict control. In cancerous tissue this process is out of control. The cells which are produced are not only abnormal in both form and function but there is a tremendous over-production of cells at the site at which the cancer has started from a single cell, and the cancerous cells may spread throughout the body. Each cell or clump of cells which spreads gives rise to a new colony of cancer cells, called a metastasis, in whatever tissue it lands.

Cancer occurs throughout the world; no country, no population is free of it. Cancer does not, however, occur with the same frequency in all countries; there are wide variations in total cancer death rates from country to country. There are also wide variations among different countries in the death rates for specific cancers.

What is the probability that a person will develop cancer?

Over their lifetime, one in three people will develop cancer and in over70% of cases it will be in those over 60 years of age. Cancers of the lung account for approximately 15% of all new cancers diagnosed with two-thirds of these being in males. For women, the most common cancer is that of the breast (approximately 18% of all new cancer diagnoses) followed by those of the reproductive system (ovary, cervix and uterus together account for 10% of all new diagnoses). In males, prostate cancer contributes 10% to all new cases diagnoses.
In both sexes there are high frequencies of skin cancers and tumors of the gastrointestinal system (19% and 13% in males and females).

What are the risk factors of cancer?

Air pollution: The ambient air in specific areas may contain industrial plant emissions, automobile exhaust, and other polluant linked to cancer, but in most places, the air we breathe does not contain highlevels of carcinogens (a causative factor of cancer).
Water pollution: Drinking water contains complex mixtures of known and suspected carcinogens including asbestos, metals, radioactive substances, and industrial chemicals. Even the process of treating water may create small quantities of chemicals linked to cancer, but the levels are so small that there is probably a low risk, if any, associated with most drinking water supplies.
Alcohol: Consumption of alcoholic beverages increases the risk of cancer, particularly of the mouth, pharynx, larynx, and oesophagus. There is no doubt that drinking and smoking together have a synergistic, or combined, effect, and do contribute to the high incidence of some cancers.
Diet: It has become clear that what we eat-or don't eat-for breakfast, lunch and dinner may have profound effects on our chances of developing cancer.
Diet and nutrition are not quite the same thing. Diet is all food and liquid you swallow. Some of this is used by the body and some goes to waste. Food is used to build the body, keep it in working order, and provide energy.
Drugs: The development of "miracle" drugs that effectively treat a variety of illness has been one of medecine's major achievement. Unfortunately, when chemically altering or arresting the course of one disease, these drugs can contribute to the development of other disease, including cancer.
Drugs are believed to account for fewer than 2% of all cancers.
Familial factors: Most cancers are caused by a variable mix of hereditary and environmental factors. Some rare cancers are inherited, and usually appear at an early age. A number of rare hereditary disorders may predispose a person to cancer but the added action of one or more environmental factors is often needed for the cancer to develop.
Ionizing radiation: Ionizing radiation is a known cause of cancer, and of other adverse effects as well. It may account for about 3% of all cancers.
Occupation: Some cancers may appear among people working in the same place, and exposed to the same chemicals or industrial carcinogens.
Solar radiation: Solar radiation is the chief cause of nonmelanoma skin cancer, responsible for about 90% of cases.
Tobacco: Cigarette smoking increases the risk of cancer of the lung more than any other site. Cigarette smoking also increases the risk of cancers of the larynx amd oesophagus.
Viruses: Although some viruses are associated with human cancers, other factors are believed to be responsible for the development of cancer.
Viruses may make cells more susceptible to the effects of radiation or chemical carcinogens, for example.

The advances in understanding cancer have been of little direct benefit to the cancer patient. For many cancers, the success of treatment is primarily determined by early detection, allowing the curative treatment of localized disease by surgery or radiotherapy. Unfortunately, the majority of cancers have already metastasized by the time of diagnosis and cannot be cured by surgery or radiotherapy alone. Major progress has unquestionably been made in cancer chemotherapy, and effective drug combinations are now capable of curing most patients suffering from several cancers.

Abdelali Haoudi

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