People with Helicobacter pylori infection are more likely to develop stomach cancer than those who are not infected with the bacterium.
The bacterium, present in the bodies of around two-thirds of the population, is the main cause of stomach ulcers, yet in most people it does not cause symptoms.
"The findings of this systematic review add to the increasing evidence that eradicating H. pylori in the general population has the potential to prevent gastric cancer," states co-author of the study Dr. Paul Moayyedi, a professor of medicine at McMaster University in Hamilton, Canada.
Gastric cancer - also referred to as stomach cancer - is the third most common cause of cancer death worldwide. According to the American Cancer Society (ACS), an estimated 10,720 people will die from this type of cancer in the US this year.
Although a leading cause of death worldwide, gastric cancer has become less prevalent in the US over the past few decades. Some doctors have speculated that this could be because people are treated with antibiotics more frequently than in the past and that these antibiotics kill off H. pylori bacteria.
The bacterium is easily treated with a one-week course of antibiotics, taken on its own or in combination with bismuth or medication to suppress stomach acid production such as proton pump inhibitors.
For the review, the researchers analyzed the findings of every randomized controlled trial comparing patients receiving at least 1 week of H. pylori therapy with patients receiving a placebo or no treatment at all. For studies to be eligible for the review, they had to follow participants for at least 2 years and feature at least two participants who subsequently developed gastric cancer.
Of the six trials that met eligibility criteria, most treated H. pylori with a combination of antibiotics with proton pump inhibitors. In all, the researchers assessed data obtained from nearly 6,500 participants.
Pertinent findings for countries with high gastric cancer rates
The researchers discovered that 1.6% of participants receiving treatment to eliminate H. pylori developed gastric cancer, compared with 2.4% of participants given no treatment or a placebo.
Due to a small number of deaths occurring, however, it was unclear to the researchers whether or not the treatment decreases the number of deaths from the disease.
The researchers suggest that the apparent association between H. pylori and gastric cancer could be explained by changes in ascorbic acid concentrations and levels of reactive oxygen species in the gut caused by H. pylori infection.
"We feel our review provides sufficient evidence for countries with high gastric cancer rates to consider population H. pylori testing and treating," concludes Dr. Moayyedi.
"More research is needed on the extent of this effect and on any potential harms of H. pylori treatment, so any country starting screening should do pilot projects to obtain more information on these issues."
Due to the findings of the study, Dr. Moayyedi believes that international guidelines for the management of H. pylori infection could change, as they add to the increasing evidence that eradicating the bacterium could potentially prevent the cancer.
"The review highlights the need for further trials in different populations to provide more evidence, and these should report both the benefits and harms of such an approach," concludes lead author Alex Ford, of the Gastroenterology Unit at St. James' University Hospital in Leeds, UK.
H. pylori was previously found by a study to potentially reduce the risk of multiple sclerosis in women by reducing immune system sensitivity.