Why is the coexistence of gastric cancer and duodenal ulcer rare? Examination of factors related to both gastric cancer and duodenal ulcer.

The coexistence of gastric cancer with duodenal ulcer has been found empirically to be rare, but why it is rare is difficult to explain satisfactorily. To elucidate this question, we carried out a literature review of the subject. The frequency with which the two diseases coexist is 0.1-1.7%, and the main factor associated with both gastric cancer and duodenal ulcer is Helicobacter pylori infection. However, there are marked differences between the disorders of hyperchlorhydria in duodenal ulcer, and hypochlorhydria in gastric cancer. The most acceptable view of the reason for the difference may be that the acquisition of H. pylori infection occurs mainly in childhood, so that the time of acquisition of atrophic gastritis may be the most important, and if atrophic gastritis is not acquired early, high levels of gastric acid may occur, and consequently acute antral gastritis and duodenal ulcer may occur in youth, whereas, in elderly individuals, persistent H. pylori infections and the early appearance of atrophic gastritis may be the causes of low gastric acid, and consequently gastric cancer may occur. In patients with duodenal ulcer, factors such as nonsteroidal anti-inflammatory drugs (NSAIDs) and dupA-H. pylori strains may contribute to preventing the early acquisition of atrophic gastritis, while acid-suppressive therapy and vascular endothelial growth factor and other entities may inhibit atrophic gastritis. In contrast, in gastric cancer, factors such as excessive salt intake, acid-suppressive therapy, polymorphisms of inflammatory cytokines, and the homB-H. pylori strain may contribute to the early acquisition of atrophic gastritis, while factors such as NSAIDs; fruits and vegetables; vitamins A, C, and E; and good nutrition may inhibit it.