H. pylori and cancer

Microscope image of helicobacter pylori bacterium

What is H. pylori?

Helicobacter pylori (H. pylori) is a type of bacteria found in the stomach. It normally infects people during childhood and infection used to be very common, but is now becoming much less so in developed countries such as the UK.

Once infected, a person usually stays infected for life unless they are treated with specific antibiotics. In the great majority of people who have it, the infection does not cause any health problems. In some people H. pylori can cause stomach ulcers.

What cancers are linked to H. pylori?

Infection with H. pylori is mainly linked to stomach cancer (especially a type called non-cardia gastric cancer). Around 4 in 10 stomach cancer cases in the UK are caused by these bacteria.

About 2 in 100 cases of Non-Hodgkin Lymphoma in the UK are linked to these bacteria as well. And there is some evidence that bowel cancer risk may also be increased in people with H. pylori infection.

As well as raising the risk of these cancers, H. Pylori is also linked to a reduced risk of oesophageal (food pipe) cancer. It’s unclear why this is the case. As H. Pylori infection rates have gone down in the UK, stomach cancer rates have dropped, but oesophageal cancer rates have risen. This is not just because of H. Pylori, but the infection could have played a part.

How can H. pylori cause cancer?

H. pylori can cause long-lasting inflammation in the stomach (called ‘severe chronic atrophic gastritis’ or SCAG) and this can lead to stomach cancer. People with SCAG have an increased risk of stomach cancer.

But millions of people around the world are infected with these bacteria and only very few (1-3 out of 100) go on to develop stomach cancer. Researchers now think this is because there are different types of H. Pylori bacteria, some of which are more likely to cause problems than others. And other risk factors such as smoking and what we eat probably also play a role.

How H. pylori may cause other types of cancer, including bowel cancer, is less well understood at the moment and more research is needed.

Reducing the risk

H. pylori infection can be detected with a blood test or a breath test. It can usually be cured fairly easily with a course of antibiotic treatment, but some infections are now becoming resistant to antibiotics.

There is some evidence that curing H. pylori infection reduces the risk of stomach cancer a little. But stomach cancer is rare, especially in countries such as the UK, and having the infection can also lower the risk of oesophageal cancer. So treating H. pylori infection is probably not in everyone’s best interest.

For this reason, your doctor may not treat H. pylori infection unless you have symptoms, such as stomach pains (a symptom of an ulcer).

In the UK, other ways to reduce stomach cancer risk are likely to have a bigger impact than treating H. pylori. This includes giving up smoking and eating a healthy, balanced diet.

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