By Gene Emery

(Reuters Health) – Eradicating the bacteria that cause stomach ulcers can slash the odds of stomach cancer by more than half among people who have had a family member develop the tumor, according to the results of a new clinical trial.

Having a family history of gastric cancer can double or triple the risk of stomach cancer. The odds are also elevated among people infected with Helicobacter pylori, or H. pylori, bacteria, which linger in the gut of about half the world’s population, the study team notes in The New England Journal of Medicine.

The new trial, which followed 1,676 volunteers for a median of 9.2 years, was an attempt to see if wiping out the bacteria using two antibiotics and a drug that blocks the production of stomach acid would cut the cancer risk. It did: by 55%.

While 2.7% of the 844 volunteers given placebo therapy developed gastric cancer, the rate was just 1.2% for those who received antibiotic therapy.

The antibiotic therapy didn’t always kill off H. pylori; the failure rate was about 30%. But when it did, the cancer rate dropped even further to 0.8%, reducing the odds of developing stomach cancer by 73%.

The results are “good news because we think that only a one- or two-week course of antibiotics can prevent gastric cancer,” lead study author Dr. Il Ju Choi of the National Cancer Center in Goyang, South Korea, told Reuters Health in an email.

He said that if someone with a family history of stomach cancer is getting an endoscopy – where a doctor looks for stomach problems by passing a tube down the throat – it is wise to test for H. pylori infection.

“If infected, then the organism should be treated,” he said. A breath test can show whether antibiotic therapy has worked. In the 10% to 30% of the cases where the bacteria are still present, different antibiotics can be tried.

Once the initial infection has been cleared, H. pylori testing doesn’t have to be done in subsequent endoscopies because the rate of reinfection is usually low – less than 2% per year in high-income countries, Choi said. But it can be 3% to 10% per year in low-income countries.

The volunteers in the new study were the parents, siblings or children of people being treated for stomach cancer at Dr. Choi’s hospital. All were infected with H. pylori, and none had a history of stomach ulcers.

There is no approved vaccine to protect against the H. pylori. Several attempts have been unsuccessful.

Dr. Choi speculated that if H. pylori could be eradicated, 80% to 90% of gastric cancer cases could be prevented in people under 40, and one third to one quarter of the cancers could be averted in older people.

For now, in the United States, because Asians and Hispanics “have much higher gastric cancer incidence, they should check their H. pylori infection status and treat the organism if family history is present,” he said.

SOURCE: The New England Journal of Medicine, online January 29, 2020.