THE PREVALENT TYPES OF CANCER ACROSS THE WORLD
There are big contrasts in the prevalent types of cancer across the world, and stomach and liver cancer are not alone in this respect. In fact, most forms of cancers show marked variation between countries that differ significantly in what might broadly be called lifestyle. Thus, for example, as recently as 2002 the chances of a woman developing or dying from breast cancer were about three times lower in Japan than in Britain or the USA (Fig. 1). Lung cancer, highest incidence, in the developed world, is rare in East Africa.
1. Worldwide variation in breast and lung cancer
We know that these differences reflect lifestyle because of what has happened when significant numbers of people have emigrated. Thus, for example, after the Second World War a considerable number of Japanese people moved to the USA: within a generation, the women had acquired the statistical profile for breast cancer of American women. Similar shifts have been observed in the incidence and mortality of colon cancer following group migrations. Even so, the gap in breast cancer incidence between the USA and Japan is closing, presumably as Western habits swamp traditional Japanese lifestyles.
The picture is, however, complicated by the fact that such differences occur not only between countries but also within national populations. Thus, for example, we noted that in the USA stomach cancer is thirteenth on the list of killers but in 2009, for every white person that this disease claims, 2.3 African Americans will die despite 66% of the population is white and only 14% African Americans. A further 15% of the USA population is Hispanic or Latino, originating mainly from Mexico, Puerto Rico, Central and South America, Cuba and Dominica, 60% of these having been born in the USA. For this group, overall cancer death rates are lower than for non-Hispanic whites (419 versus 574/100,000 in the period 2000–2003). This is because of the rates for the major cancers (prostate, breast, colorectal and lung) are lower although Hispanic rates are higher for stomach, liver, cervix, and acute lymphocytic leukaemia and gallbladder cancers. This difference appears to be more sustained than occurred in the cohorts of migrants mentioned earlier, but the cancer rates in descendants of Hispanics are nevertheless approaching those of non-Hispanic whites.
For the Caribbean (Fig. 2) the overall cancer mortality rate is similar to that of South America (around 120 per 100,000) but both are significantly greater than in Central America (92).
Taken together the average cancer mortality for Latin America is somewhat below that of North America (Canada and the USA being very similar). As might be anticipated, the rates vary markedly between countries. For men, Uruguay, Argentina and Chile have the highest mortality and for women, it is Colombia and Chile. A significant factor is tobacco use, which varies widely across the region but is high in Uruguay where the male lung highest in Latin America. In Argentina male lung, prostate and colorectal cancers are high but in Chile, Colombia, Ecuador and Peru stomach cancer is the major male cancer and, for females in those countries, it is also one of the most common, together with cervical cancer. The latter, together with breast cancer, are major causes of female death throughout South America. There is some evidence that stomach cancer deaths may be declining across Latin America as food quality improves. However, the effect of smoking together with the trend towards excess weight and obesity in the entire region is a significant factor in the increased cancer mortality evident in most countries, Chile being an exception where there has been a slight fall since 1996.