Treating a bacteria that commonly causes stomach ulcers may reduce the burdens of cancer.
Otago University researchers are recommending a programme to test for Helicobacter pylori.
Diana Sarfati, lead author of a new study published in the Journal of the Royal Society of New Zealand, says it will be beneficial for Māori and Pacific people - where the rates are three to six times higher.
"We've worked out the majority of that excess is due to higher rates of infection with a bacteria called H. pylori."
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Nine out of 10 people who go on to get cancer in a particular part of the stomach have been infected with H. pylori.
Treating the bacteria with tools, including antibiotics, significantly reduces cancer incidence - by up to a third.
Dr Sarfati says getting on top of it early could help a lot of people, and be cost-effective.
"You tend to get it in childhood. It's more common if people are living in overcrowded conditions or children are growing up in poverty."
But more research is needed.
"All the information on it is really old. We know that around the world, H. pylori infection is coming down - it's getting less common."
Dr Sarfati says it could help predict what will happen with stomach cancer in two or three decades.