Cancers
Cells in our bodies are always dividing, as new cells replace old ones. 36Cancer cells divide rapidly, and form growths called tumours(肿瘤）. They can spread to take over a whole organ and stop it working properly. If cells break away from the tumour, they can travel to other parts of the body and start new tumours.
We do not know why some people get cancer while others don’t. But faulty genes are certainly the cause of some cancers. Others are caused by chemicals in the environment.
Cancer is not a single disease. 37 The most common types affect the digestive system and lungs. In women, cancers of the breasts and cervix (子宫颈) are also common.
Smoking is the cause of almost all cases of lung cancer. Tobacco smoke contains chemicals which can damage the lungs. The more cigarettes a person smokes, the greater their risk of suffering from lung cancer. 38
Cancers of the skin are also quite common. Many types of radiation, especially ultraviolet rays (紫外线) from the Sun, can damage skin cells and cause cancer.
Most cancers can be treated successfully if they are caught early enough. Some treatments involve surgery to remove the tumour. This is often followed by a course of strong drugs. 39 They kill healthy cells as well as cancer cells.
In the most up-to-date treatments, drugs are delivered directly to the cancer cells using “magic bullets”. These are special antibodies which only attach themselves to cancer cells.
Similarly, radiotherapy(放射疗法) is a type of cancer treatment which uses radiation to kill cancer cells. A narrow bean(光线) of radiation is focused directly at a tumour. 40
A. Most skin cancers are completely curable.
B. And the healthy cells nearby are not damaged.
C. Many of these drugs have unpleasant side-effects.
D. An X-ray of the lungs shows the position of a tumour.
E. Different cancers can affect almost any part of the body.
F. But sometimes the process goes wrong, and a cancer cell is formed.
G. Fortunately, the risk of getting cancer is reduced when someone stops smoking.