Australasian Science: Australia's authority on science since 1938

Helicobacter Protects Against Cancer

By Stephen Luntz

The bacterium that causes stomach ulcers provides protection against an increasingly common form of cancer.

Adenocarcinomas are one of two types of oesophageal cancers. Although globally they are less common than squamous cell cancers, they now make up 60% of oesophageal cancers in Australia – and rising.

Dr David Whiteman of the Queensland Institute of Medical Research says: “Unfortunately the prognosis is very bad. Median survival is 1–2 years. By the time most people present with symptoms the tumour is usually really large.”

Some previous research had indicated there might a negative correlation between infection with Heliobacter pylori and oesophageal cancer. However, the evidence was not clear and, as Whiteman says: “We know that H. pylori infection causes gastritis, stomach ulcers and cancers of the stomach, so it might seem odd to propose that this germ could also have benefits”.

However, a comparison of 800 people with oesophageal cancer and 1400 without confirmed that having H. pylori is protective against adenocarcinomas but not against squamous cell cancers.

Whiteman says that rising rates of adenocarcinomas in the developed world may partly be driven by falling rates of H. pylori, both through better hygiene and ulcer medication. “However, we believe rising obesity is a bigger factor, since body fat is known to be a major contributor.”

The mechanism remains unknown, but Whiteman says the most likely theory is that H. pylori reduces the acidity of the stomach in some people. Bouts of acid reflux can bring the stomach acids into the oesophagus, and it may be that acid damage contributes to cancer formation. “It’s also possible there is an immune response that creates a change in the lining of the oesophagus,” Whiteman says.

But anyone suffering from stomach ulcers does not need to choose between reducing their pain and risking their life. “Stomach ulcers can puncture, leading to death, and H. pylori can cause stomach cancers, which are much more common than oesophageal cancers, so you’re much better off getting ulcers treated and accepting the minimal increase in risk of getting adenocarcinoma,” says Whiteman.