Helicobacter pylori, peptic ulcer and gastric cancer in China.

INTRODUCTION Recent epidemiological evidence supports a strong relationship between Helicobacter pylori infection and gastric cancer [1-11]. The relative risk for cancer with an infection of five years and over is in the region of three to six (Table 1). The identification of almost universal coexistence of H. pylori related antral gastritis in patients with duodenal ulcer disease [12, 13] and the subsequent proof of significant reduction in duo-denal ulcer relapse rate after successful eradication of the organism [14-16] forms the platform that H. pylori infection is aetiologically related to duodenal ulceration. Although the relationship between H. pylori infection and gastric ulcer disease appears less convincing than that between H. pylori infection and duodenal ulcer disease, there has been recent evidence from therapeutic study that successful eradication of the organism helps to reduce the gastric ulcer relapse significantly [17]. It is generally accepted that patients with duodenal ulcer seldom develop gastric cancer, the chance of an associated gastric cancer having been estimated to be one-fifth of that of gastric ulcer [18]. It thus appears that H. pylori infection occupies a common ground for three divergent conditions. Geographical differences in the prevalence of peptic ulcer within the same country have been well described, such as the higher frequency in the north than in the south of India, in Scotland than in England, or in the west than in the east of Australia [19-21]. However, the relationship of the ulcer and cancer distribution within any one country, which may have pathogenetic implications, has not been examined, probably because not many countries are known to have a high prevalence of both conditions. China is a vast country where duodenal ulcer, gastric ulcer and gastric cancer are known to be prevalent and where a systematic study of the distribution of peptic ulcer and gastric cancer has not been reported in the English literature. Such information, together with the knowledge of the H. pylori prevalence should throw light on the pathogenesis of these H. pylori related conditions. This forms the basis of this review.