THURSDAY, July 31 (HealthDay News) -- In patients who've had surgery for stomach cancer, removing Helicobacter pylori bacteria from the stomach greatly reduces the risk of cancer recurrence, a Japanese study finds.

Almost all stomach cancers not related to the heart develop from H. pylori, which has been classified as a group I carcinogen for stomach cancer by the World Health Organization, according to background information in the study.

While removal of H. pylori has been shown to have a preventive effect on stomach cancer in animals, trials in humans have produced mixed results.

This new study included 544 patients who had surgery to remove early stomach cancer. Half of them received an H. pylori eradication regimen, while the other half received no treatment. The eradication group received 30 milligrams of lansoprazole twice daily, 750 milligrams of amoxicillin twice daily, and 200 milligrams of clarithromycin twice a day for a week.

All the patients were examined at 6, 12, 24 and 36 months for signs of stomach cancer. After three years, stomach cancer had recurred in nine eradication group patients and in 24 control group patients. The eradication group patients were two-thirds less likely to suffer cancer recurrence than those in the control group, the researchers said.

The findings were published in this week's issue of The Lancet.

"The results of our study suggest that treatment to eradicate H. pylori reduces the risk of developing new gastric carcinoma in patients who have a history of such disease and are thus at risk for developing further gastric cancers ... we believe that our data add to those from previous studies showing a causal relationship between H. pylori infection and gastric cancer, and also support the use of H. pylori eradication to prevent the development of gastric cancer," the researchers concluded.

In an accompanying commentary, Dr. Nicholas Talley, of the Mayo Clinic in Jacksonville, Fla., noted that colonoscopy is widely used to screen for colorectal cancer even though there are no published randomized trials of benefits versus risks.

"Yet, worldwide, gastric cancer kills more people, and there is better evidence that H. pylori eradication can prevent mortality than there is for colonoscopy screening. Preventing gastric cancer by eradicating H. pylori in high-risk regions should be a priority," Talley wrote.

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