Abstract
Two histological types of gastric cancer, intestinal-type and diffuse-type, have different carcinogenesis pathways. Incresed risk for gastric cancer was observed among A-bomb survivors. The objective of this study was to determine the A-bomb radiation effects on histological atypism of gastric cancer, after adjusting for potential risk factors.
The study was designed as a nested case-control study with 299 gastric cancer cases occurring in a cohort of about 20,000 individuals followed up biennially through health examinations in Hiroshima and Nagasaki since 1958. Three controls per case matched on birth year, gender, and city. There were 152 intestinal-type non-cardiac gastric cancer cases and 147 diffuse-type non-cardiac gastric cancer cases.
H. pyroli infection and atrophic gastritis were independent risk factors of both intestine- and diffuse-type non-cardiac gastric cancer. Neither radiation exposure nor smoking was related to risk for intestinal-type, after adjusting for H pylori infection and atrophic gastritis. However, increased risk of diffuse-type gastric cancer with radiation dose was found among non-smokers with marginal significance. Relative risk of diffuse-type non-cardiac gastric cancer was 2.2 per 1Gy (95% confidence interval 0.85-3.72 p=0.08) among non-current smokers.
The nested case-control study among A-bomb survivors suggested that radiation exposure increased risk of diffuse-type non-cardiac gastric cancer among non-smokers, but not intestinal-type, after adjusting for the risk factors.
