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Helicobacter pylori Strain Linked to Gastric Cancer

Odds for precancerous changes are great in patients infected with specific strain of Helicobacter pylori

THURSDAY, Aug. 30 (HealthDay News) -- Infection with strains of Helicobacter pylori expressing the cytotoxin-associated (cagA) gene is strongly associated with precancerous gastric lesions, reports a study published online Aug. 28 in the Journal of the National Cancer Institute.

Martyn Plummer, of the International Agency for Research on Cancer in Lyon, France, and colleagues analyzed gastric biopsy specimens from 2,145 Venezuelan participants to determine the relationship between H. pylori infection, particularly strains expressing the cagA gene, and gastric cancer. Participants were followed with yearly gastroscopies to evaluate progression of lesions over a mean of 3.5 years.

A strong association was found between H. pylori strains expressing the cagA gene and precancerous gastric lesions, but cagA-negative strains were only associated with chronic gastritis. Of patients with dysplasia or precancerous changes, 75 percent had evidence of cagA-positive H. pylori infection, whereas 17 percent of patients with normal gastric mucosa were cagA-positive. Compared with uninfected individuals serving as controls, the odds ratio for dysplasia was 15.5 in cagA-positive individuals and 0.90 for cagA-negative individuals.

"The proportion of all gastric cancers worldwide attributable to H. pylori was estimated to be 63 percent. Our results imply that, in populations with a high prevalence of cagA-positive H. pylori, the attributable fraction may be even higher," the authors conclude.

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