[Helicobacter pylori and gastric cancer]. / Helicobacter pylori e cancro gastrico.

ABSTRACT

Several unresolved issues still cast doubts on the epidemiological data which point to an association between infection from Helicobacter pylori (Hp) and gastric cancer. These are a) the male/female ratio of gastric cancer ranges from 4 to 1.5 in all studies, whereas the prevalence of Hp infection is the same in both sexes; b) the prevalence of Hp infection is as high as 90% in several developing countries where the frequency of gastric cancer is very low; c) the acquisition of the infection at a young age, considered very important with regard to the risk for cancer, varies from 4.2% to 83% in several countries in which the mortality for stomach cancer is, on the average, 10/100,000; d) the incidence of cancer in patients with a duodenal ulcer is half of that of the general population but Hp infects up to 100% of these patients. In the sequence of events that lead to gastric cancer, Hp appears to play a role only in the very initial steps, as a causative agent of chronic inflammation. The further events which lead to cancer are multifactorial, involving environmental agents and the host response. It is therefore inappropriate to consider Hp a direct carcinogen for humans. This also applies to specific strains of the bacterium such as the ones expressing the cagA gene. In a study we conducted in an area with a low incidence of gastric cancer (Latina), the prevalence of Hp infection was equal to 78.6% and, among the positives, 81% resulted cagA positive. This data, if compared with a similar research that took place in another area with a high incidence of gastric cancer (San Marino) where the prevalence of Hp infection was 51% and cagA 69%, further demonstrates the inconsistency of associating Hp and cancer of the stomach.