Does a Helicobacter infection in your stomach increase your risk of stomach cancer?

Yes, an infection with the stomach bacterium Helicobacter pylori demonstrably increases your risk of stomach cancer. The bacterium has been officially classified as a proven carcinogen and is considered the single largest known risk factor for stomach cancer. Yet the risk for any individual is smaller than you might expect: of all infected people, roughly 2% ultimately develop stomach cancer, and another 20% or so develop pre-cancerous conditions. More than half of the world's population carries the bacterium.

Whether you develop cancer depends strongly on the type of bacterium. Strains carrying certain proteins, particularly CagA and VacA, are more dangerous than strains without those proteins. Alongside the bacterial type, your genetic predisposition and environmental factors also play a role. Someone with an aggressive bacterial strain and an unfavourable genetic profile therefore has a considerably higher personal risk than someone with a milder strain.

The good news is that eradicating the bacterium with antibiotics works. Large studies involving tens of thousands of people show that those who are successfully treated have nearly half the risk of stomach cancer compared with those who remain untreated. This holds true even for people aged 70 and older, and the earlier treatment is given, the greater the benefit. Treatment is even worthwhile after early-stage stomach cancer has already been removed, to prevent recurrence.

One complication is that H. pylori is increasingly resistant to the standard antibiotics. As a result, standard therapies often fail to work. If you are being treated for an H. pylori infection and symptoms persist, it is wise to ask whether the bacterium has actually been eliminated.