Significance of Helicobacter pylori infection as a risk factor in gastric cancer: serological and histological studies.

We conducted a case-control study to examine the association of Helicobacter pylori infection as a risk factor in gastric cancer in the Japanese population. Serum IgG antibodies for Helicobacter pylori were determined in 55 consecutive patients with gastric cancer and in 75 age- and sex-matched mass survey subjects and 57 age- and sex-matched cancer-free patients with conditions considered at a high risk for development of gastric cancer (precancerous condition). We examined the histology in all subjects and particular focus was placed on the extent of Helicobacter pylori-associated gastritis. The seroprevalence of Helicobacter pylori in gastric cancer patients (82%) and those with a precancerous condition (89%) was significantly higher (P < 0.005) than that in the mass survey subjects (60%). Positive relative risk associations were found for patients with gastric cancer (odds ratio, 3, with 95% confidence intervals of 1.69-5.33) and those with a precancerous condition (odds ratio, 5.66, with 95% confidence intervals 2.66-12.03). Significant differences were found when comparisons were made among the case-control groups who were H. pylori-positive and had inflammatory cell infiltration (P = 0.0127). The characteristics of Helicobacter pylori in histologically examined gastric mucosa showed differences between Helicobacter pylori-infected and uninfected persons in all groups. However, for none of these groups was there a significant differences between background mucosa for Helicobacter pylori-infected persons with or without gastric cancer. Helicobacter pylori seroprevalence is strongly associated with an increased risk of gastric cancer and with a precancerous condition; histological investigation did not define additional factors that might be associated with increased cancer risk.