Is Helicobacter pylori a causal agent in gastric carcinoma?

Long-term Helicobacter pylori infection and the development of atrophic gastritis and gastric cancer in Japan

The incidence of gastric cancer and the prevalence of Helicobacter pylori are high in Japan, so it is an important issue whether long-term H. pylori infection leads to chronic atrophic gastritis, considered one of the precursors of gastric cancer. We have reported that the grade of atrophy was higher in H. pylori-positive subjects than in H. pylori-negative subjects. It has also been reported that the atrophy of gastric mucosa increased in H. pylori-infected monkeys compared with control monkeys in a 5-year follow-up study. Most H. pylori infections occur in children, and atrophy of the gastric mucosa progresses during aging. Long-term data show that H. pylori infection can lead to gastric atrophy and may play an important role in the development of gastric cancer. Interestingly, there was no difference in the prevalence of H. pylori between patients with chronic gastritis and gastric cancer in Japan, but the prevalence of H. pylori in young Japanese gastric cancer patients was significantly higher than in the control group. These data clearly show that H. pylori infection is one of the risk factors of gastric cancer in young Japanese people, There is no answer to whether curing H. pylori infection can reverse the atrophy of the gastric mucosa and decrease the risk of gastric cancer development. To clarify this issue, an intervention study must be done. A large clinical trial called the Japanese Intervention Trial of H. pylori is in progress.

Helicobacter pylori infection, serum pepsinogen level and gastric cancer: a case-control study in Japan

We conducted a case-control study to evaluate the effect of Helicobacter pylori (HP) infection on the risk of gastric cancer in Tokyo, Japan. The sera at the time of diagnosis from 282 gastric cancer cases and 767 sex- and age-matched cancer-free controls were tested for the presence of anti-HP IgG antibody (HM-CAP ELISA kit) and serum pepsinogen (PG) level (PG I and PG II Riabead). No significant association was observed in all sets [matched odds ratio (OR) = 1.04, 95% confidence interval: 0.73-1.49]. In subgroup analyses, however, an association was suggested in females [OR = 1.57], a younger population (< 50 years) [OR = 1.86], early cancer [OR = 1.53] and small cancer (< 40 mm) [OR = 1.55]. Furthermore, we observed a tendency for odds ratios to decrease with an increase in age or cancer growth (depth of tumor invasion and tumor size). Considering that the spontaneous disappearance of HP due to extended mucosal atrophy may lead to these decreasing odds ratios, we applied the conditional logistic model adjusted for the PG I/II ratio as a measure of atrophic gastritis. This analysis showed a positive association with HP infection in all sets [OR = 1.69; 1.01-2.81], distal cancer [OR = 1.88; 1.07-3.31] and intestinal-type cancer [OR = 3.76; 1.39-10.18]. We concluded that the risk of cancer associated with HP infection may be underestimated in studies with cross-sectional exposure because of spontaneous disappearance of HP due to extended mucosal atrophy.