According to the report, the eight most common cancers worldwide in terms of incidence are also the eight which cause most deaths. These are cancers of the lung, stomach, breast, colon/rectum, mouth, liver, cervix, and oesophagus. Together they accounted for about 60% of the 6.3 million cancer deaths and 10.3 million cancer cases in 1996.
The number of cases and deaths for each is as follows:
|Site||Cases Female||Cases Male||Cases Both Sexes||Deaths Total|
|Lung||390 000||990 000||1 320 000||989 000|
|Stomach||380 000||635 000||1 015 000||776 000|
|Colon-rectum||430 000||445 000||875 000||495 000|
|Liver||165 000||375 000||540 000||386 000|
|Breast||910 000||---||910 000||376 000|
|Oesophagus||160 000||320 000||480 000||358 000|
|Mouth||190 000||385 000||575 000||324 000|
|Cervix||525 000||---||525 000||247 000|
(Note: The number of deaths from a disease in any year do not relate only to new cases of the disease occurring in that year, but also to cases occurring in previous years).
In all of these cancers, at least one lifestyle factor plays an important role. The most worrying trend is the increasing number of women developing either lung cancer or breast cancer.
Lung Cancer: Incidence rates of lung cancer in men are increasing in most countries. In countries where the smoking epidemic first began, and has now passed its peak, they are beginning to fall - for example in Finland, the United Kingdom and the United States. Among women, incidence rates are rising briskly in countries where female smoking is long established. Lung cancer is now the commonest cause of death from cancer in women in the US. In the European Union countries, a 33% increase in female lung cancer cases is predicted by 2005. Worldwide, about 85% of lung cancers in men and 46% in women are tobacco- related. The ratios in developed countries are 91% and 62%. There is no effective treatment for lung cancer. Only 7%-12% of patients are alive five years after diagnosis.
Stomach cancer: The steady decline in cases in most industrialized countries during the last 30 years is attributed to nutrition richer in vitamins from fresh fruits and vegetables, and less consumption of preserved, cured and salted foods. But the disease is the second most common cancer worldwide, and almost two-thirds of all cases are in developing countries. Infection with the bacterium Helicobacter pylori contributes to the risk of the cancer. Only about one patient in five survives longer than five years after diagnosis.
Colorectal cancer: Studies show a higher risk of colorectal cancer in people eating a diet low in vegetables, legumes and whole cereals. Frequent consumption of red meat increases the risk. Although it is more common in richer countries, incidence of the disease is rising in some developing countries. Incidence increases rapidly in the first generation of migrants moving from a low-risk country, such as Japan, to a high-risk country, such as the United States. If diagnosed at an early stage, 90% of patients survive at least five years, compared to no more than 8% of those diagnosed at an advanced stage.
Liver cancer: A major problem in developing countries, with China alone accounting for 55% of all cases. The risk is twice as high in men as in women everywhere; 83% of all cases are attributable to infection with hepatitis B virus. Most other cases are linked to excessive alcohol consumption. Only about 6% of patients survive more than five years.
Breast Cancer: More than half of all cases are in industrialized countries. Incidence is in-creasing in most parts of the world, particularly in regions which previously had low rates. Studies show that the incidence in women who migrate from low to high-risk regions, slowly rises, over two or three generations, to the rates of the host country. This illustrates the importance of lifestyle as well as hormonal risk factors in the development of the disease. Other risk factors are obesity after menopause, and diet, in particular too high a consumption of animal fats. At least half of breast cancer sufferers survive at least five years after diagnosis.
Oesophageal cancer: Tobacco and alcohol are the most important risk factors, particularly in combination. Smoking accounts for 45% of cases in men worldwide, but only 11% of female cases. About 85% of cases are in developing countries. About 75% of patients die within a year of diagnosis: only 5-10% survive for five years.
Mouth cancer: Tobacco and alcohol consumption are again major risk factors. Three out of four cases worldwide are in developing countries. Studies indicate a protective effect of a diet rich in vegetables and fruit. Five-year survival from the disease ranges between 80% in its early stages to as low as 5% in advanced cases.
Cervical cancer: Eighty per cent of cases occur in developing countries, where it is often the most common cancer in women. Cases and deaths have declined markedly in many industrialized countries, mainly because of extensive screening programmes. The sexually-transmitted human papilloma virus is found in more than 95% of cases; it is a necessary but probably not sufficient cause of the disease. A vaccine against the virus is being developed. Survival depends on the stage of the disease at diagnosis, with 90% of localized cases surviving five years compared to less than 10% with distant spread.