Removal of bacteria reduces risk of stomach cancer redeveloping

Treating any Helicobacter pylori infection in the stomachs of people who have been treated for gastric (stomach) cancer appears to reduce the risk of cancer redeveloping, a Japanese study has found.

The bacterium Helicobacter pylori (H. pylori) has been classified as a group I carcinogen for stomach cancer by the World Health Organisation, and studies have suggested that infection with the bacterium increases stomach cancer risk up to five-fold.

But it is not yet known for certain that treating the infection reverses this increase.

To investigate the effects of treating H. pylori, a team of researchers at Hokkaido University Graduate School of Medicine and the Japan Gast Study Group carried out a study involving 544 patients.

They found that treating H. pylori infection decreased the incidence of further 'metachronous' stomach cancers in patients who have previously been operated on for the disease.

Metachronous stomach cancers are cancers that develop at a new site in the stomach, but do not actually develop directly from the original cancer.

A total of 272 patients were treated with lansoprazole to reduce the production of stomach acid, and the antibiotics amoxicillin and clarithromycin to eradicate H. pylori, while the remaining 272 received no such treatment.

Publishing their findings in the Lancet medical journal, the researchers reveal that after three years, 24 patients in the untreated group had developed metachronous gastric cancer, compared with just nine patients who had been treated to remove the bacteria.

The researchers concluded: "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."

Writing in an accompanying editorial, Dr Nicholas Talley from Florida's Mayo Clinic said that preventing gastric cancer by eradicating H. pylori "should be a priority".

Henry Scowcroft, science information manager at Cancer Research UK, said: "This result adds to our understanding of the relationship between H. pylori and stomach cancer, and to the debate on how we should treat people with this infection.

"Cancer Research UK is helping fund a long-term trial specifically looking at whether treating H. pylori can prevent stomach cancer. The trial aims to recruit 56,000 people across the UK, treat any who show signs of H. pylori infection, and follow them over 15-20 years to see if this treatment is effective."

(Source: Lancet: Cancer Research UK: August 2008)