How long will it take to reduce gastric cancer incidence by eradicating Helicobacter pylori infection?

Helicobacter pylori (H. pylori) is the most important risk factor for the development of gastric cancer. The objective of this article is to estimate how the number of clinically diagnosed cases caused by H. pylori would reduce in the years after the eradication of the infection from a population. It is assumed that the eradication of H. pylori will prevent the start of some new gastric tumors, but those that have passed the "point of no return" will continue to develop until diagnosed clinically. The observed reduction in the number of clinically diagnosed cases of gastric cancer will depend on the form and parameters of the distribution of the time t taken for tumor to develop into a clinical case after passing the "point of no return." This analysis assumes that the time t follows normal and log-normal distributions with means 5, 10, and 15 years. If the mean value of time t were 5 years, H. pylori caused cases should be almost eliminated after 10 years, whereas if the mean were 10 years, the number of cases should be halved. If the mean were 15 years, the reduction would only be about 15% after 10 years. The eradication of H. pylori from a population will reduce the incidence of gastric cancer, but the follow-up time needed to show and evaluate the reduction may be longer than that that has been used in studies published so far.