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Cancer: the growing burden
More than 10 million people developed cancer in 1996 and over 6 million others already having the disease died of it. The gradual elimination of some other fatal diseases, combined with rising life expectancy, means that the risks of developing cancer are steadily growing.
As most cancers appear in adults at an advanced age, the burden of cancer is much more important than other diseases in populations with a long life expectancy.
The eight leading cancer killers worldwide are also the eight most common in terms of incidence. Together, they account for about 60% of all cancer cases and deaths. They are cancers of the lung, stomach, breast, colon-rectum, mouth, liver, cervix and oesophagus. Although they do not share the same risk factors, a few major factors dominate this group, namely diet, tobacco, infections, alcohol and hormones.
The most ominous trends are in lung cancer and breast cancer. Lung cancer is not only the biggest killer and the most common of cancers - almost a million deaths a year and over 1.3 million cases - it is also preventable. Globally, 85% of cases in men and 46% in women are due to smoking. Rates for men are increasing in most countries, and rates for women are rising rapidly in countries where female smoking is long established. As tobacco consumption is increasing in many developing countries, the lung cancer epidemic seems certain to continue and grow.
Lung cancer is the most common cancer in men in developed countries, followed by prostate cancer.
In 1996 there were an estimated 17.9 million persons with cancer surviving up to five years after diagnosis. Of these, 10.5 million were women, 5.3 million of whom had cancer of the breast, cervix or colon-rectum. Among men, prostate, colorectal and lung cancer were the most prevalent.
Breast cancer kills 376 000 women a year worldwide and there are about 900 000 new cases annually. Incidence is increasing in most parts of the world. In developing countries, breast cancer is now almost as common as cervical cancer, the leading female cancer in the developing world. Unlike cervical cancer, however, breast cancer has no infectious agent to explain its rising incidence.
Stomach cancer is the second most common cancer worldwide and almost two-thirds of all cases are in developing countries. Colorectal cancer is more common in richer countries but its incidence is rising in some developing nations. The majority of cancers of the liver, mouth, oesophagus and cervix occur in developing countries. The risk of developing those cancers that are typical of higher socioeconomic groups - cancers of the breast, colon and rectum - can be expected to increase with economic development.