Background: Helicobacter pylori (H. pylori) infection has been classified as a group I carcinogen for gastric cancer by International Agency for the Research on Cancer since 1994. The findings from several epidemiological studies in Asian countries, however, showed inconsistent results regarding the association between H. pylori infection and gastric cancer. We conducted a nested case-control study to evaluate the potential role of H. pylori infection on the gastric adenocarcinoma development in a Korean cancer cohort. Methods: The KMCC (Korean Multi-center Cancer Cohort) had stored serum or plasma from the study participants for the molecular epidemiological studies of cancer causes since 1993. Occurrence of stomach cancer patients was identified through active and passive surveillance using both the Central Cancer Registry database and the National Health Insurance Cooperation database. Medical record review with detailed clinical information including cancer stages, histologic types and subsites was conducted for potential gastric cancer patients. Four controls from the eligible cancer-free cohorts were matched to each cancer case by age, sex, site and year of recruitment. H. pylori IgG enzyme-linked immunosorbent assay (ELISA) was tested for serum or plasma samples of the cases and controls. A conditional logistic regression model was used to estimate the matched odds ratio and 95% confidence intervals. Results: Of the 10,581 men and women without previous cancer history recruited between 1993 and 2000, 82 newly developed gastric cancer cases were identified by December 2001. Seropositivity of the cases was 84.2% and that of the 328 matched controls was 81.7%. The odds ratio for H. pylori infection to gastric cancer was 1.03 (95% CI 0.78-1.37). In subgroup analysis, non-cardia cancer cases (OR 1.18, 95% CI 0.79-1.75), cases followed more than 5 years (OR 1.22, 95% CI 0.60-2.49) and subjects with no peptic ulcer history (OR 2.54, 95% CI 0.72-8.91) showed non-significantly increased risk. Conclusion: This study suggests no association between H. pylori infection and gastric cancer risk in Korean although subgroup analysis showed insignificantly increased risk. This study is the first nested case-control study within population-based prospective cohort including both males and females in Asia area with high prevalence of H. pylori infection on the association between H. pylori infection and gastric cancer. Relatively small sample size for the analysis on different subsites is a limitation of this study. Further investigations on the subtypes of H. pylori, genetic susceptibility of the host, and their interaction with dietary antioxidants with sufficient years of observation and numbers of cohort are considered in the next study.

[Proc Amer Assoc Cancer Res, Volume 45, 2004]