Ridding the gut of the ulcer-causing bacterium Helicobacter pylori could prevent stomach cancer in people with a family history of the disease.

H. pylori infects more than half of all people, and has been linked to peptic ulcers and gastric cancer, which kills more people worldwide than all but two other cancers. Il Ju Choi at the National Cancer Center in Goyang, South Korea, and his colleagues studied 1,676 people with H. pylori infection who had a close relative with stomach cancer. Half of the participants received a placebo. The other half received a cocktail of antibiotics, which eradicated H. pylori in most but not all of the participants who took the drugs

About 9 years later, 1.2% of participants who had been treated with the cocktail had developed stomach cancer, compared with 2.7% of those who had received the placebo. Stomach cancer occurred in only 0.8% of those whose H. pylori population had been eradicated, compared with 2.9% of those who remained infected.