CARTAS LETTERS

Aspects of gastric cancer epidemiology with special reference to Latin America and Brazil  

Aspectos epidemiológicos do câncer gástrico com referência especial à América Latina e Brasil

Nubia Muñoz

International Agency for Research on Cancer
Lyon, France  

The most recent estimates of world-wide incidence indicate that gastric cancer is the second most frequent cancer in the world, with over 700,000 new cases per year. In developing countries, however, it still ranks first in males despite the fact that steady declines have been observed everywhere. Large differences in incidence exist even within small geographical areas and within a given country.

In Latin America, cancer registries from Costa Rica, Ecuador, and Colombia report incidence rates 3-4 times higher than cancer registries from Paraguay and Cuba. In Brazil, incidence rates are twice as high in the North (Belem) as they are in the South (Campinas, Porto Alegre).

However, despite the declining time trends in rates, the absolute number of gastric cancer cases will increase everywhere for two main reasons: ageing of the population and the tendency of the decreasing trends to level off. For example, in 1985 the absolute number of gastric cancer deaths occurring in Latin America and Brazil was 30,500 and 17,300, respectively, and the expected figure for the year 2000 is 46,100 for Latin America and 26,200 for Brazil. Thus, the magnitude of the public health problem posed by gastric cancer will increase.

The exact causes of the decline of gastric cancer and of the observed geographical differences are not well understood, but must include improvements in diet, food preservation (refrigeration), and possibly a decline in Helicobacter pylori infection.

From the point of view of diet, a decrease in the consumption of preserved or salty foods and an increase in the intake of fresh vegetables and fruits may be partially responsible for the decline. H. pylori infection is accepted today as the most common cause of gastritis and therefore the initiator of the chain of events that leads to gastric cancer.

Eradication of this bacterium by different antibiotic regimens does not seem to be the best approach to the long-term control of the infection. Our studies in a high-risk population for stomach cancer in Venezuela have shown that antibiotic combinations that are successful in eradicating H. pylori in European and North-American populations do not work in these Venezuelan populations. Possible explanations may be differences in the strains of H. pylori, including resistance to antibiotics, or frequent re-infection. These findings have far-reaching implications for strategies directed at preventing gastric cancer by eliminating or reducing H. pylori infection. In addition to the relative inefficacy of the various antibiotic regimens, their cost is not negligible.

In developing countries, therefore, the road to primary prevention of gastric cancer by eliminating H. pylori infection lies in the development of safe and effective vaccines.