Causal role of Helicobacter pylori infection in gastric cancer: an Asian enigma

Abstract

Helicobacter pylori (H pylori) has been etiologically linked to gastric cancer.H pylori infection is more frequent in less developed Asian countries like India, Bangladesh, Pakistan,and Thailand and is acquired at early age than in more developed Asian countries like Japan and China. Frequency of gastric cancer, however, is very low in India, Bangladesh, Pakistan and Thailand compared to that in Japan and China. Similar enigma has been reported from Africa as compared to the West. Seroprevalence of H pylori infection in adult populations of India, Bangladesh, Pakistan and Thailand varies from 55% to 92%. In contrast, seroprevalence of H pylori in Chinese and Japanese adults is 44% and 55%,respectively. Annual incidence rate of gastric cancer in India, Bangladesh, and Thailand is 10.6, 1.3, 7.1 per 100,000 populations, respectively; in contrast, that in China and Japan is 32-59 and 80-115 per 100,000 populations, respectively. Several studies from India failed to show higher frequency of H pylori infection in patients with gastric cancer than controls. Available evidences did not support difference in H pylori strains as an explanation for this enigma. Despite established etiological role of H pylori, situation is somewhat enigmatic in Asian countries because in countries with higher frequency of infection,there is lower rate of gastric cancer. Host's genetic make-up and dietary and environmental factors might explain this enigma. Studies are urgently needed to solve this issue.

Figure 1

Map of Asia showing frequency of Helicobacter pylori infection in each country, crude annual incidence of gastric cancer per 100 000 populations (shown within parenthesis, where data are available). The reference from where data are obtained is shown in superscript. A: frequency in the year 1984; B: lower annual incidence of gastric cancer for Indians and higher values for Chinese living in Singapore; C: studies using PCR among patients with dyspepsia; #: annual-age standardized incidence rates; $: annual age-standardized death certification rate estimated from the graph that appeared in the report (year 1998-99).