Carriers told to have stomachs removed.

Researchers have come up with the first precise risk estimates of people developing stomach cancer if they have inherited certain gene mutations. This matters because people diagnosed with one of the mutations leading to hereditary diffuse gastric cancer, a rare disease, are recommended to have their stomachs surgically removed.

Previously the best estimate was that 70 per cent of people with the mutations of the E-cadherin (CDH1) gene would develop stomach cancer.

Now University of Otago researcher Professor Parry Guilford and colleagues overseas have analysed 75 families with a strong family history of the deadly cancer, including a Bay of Plenty whanau who lost 25 members to the disease in 30 years.

Among those with a CDH1 mutation, the risks of developing stomach cancer are 70 per cent for men and 56 per cent for women. Women with the mutation also have a 42 per cent risk of developing lobular breast cancer, a type of breast cancer that is harder to detect by mammography than other forms of the disease, often delaying its diagnosis.

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Professor Guilford said the now-accurate risk estimates would help patients to make better-informed decisions about whether to have preventive surgery to remove their stomachs or a breast - or to opt instead for surveillance, which includes an annual endoscopy, a check via a viewing tube down the oesophagus. About two-thirds of those told they have the mutation choose surgery. "We recommend people take the surgical option. That way they can be guaranteed not to get stomach cancer."

Cases caused by a CDH1 mutation account for around 2 per cent of gastric cancer and less than 1 per cent of breast cancer. Professor Guilford's group is trying to find drugs to treat CDH1-mutation tumours.

Mutation detected
Q. What are the diseases?
A. Rare forms of stomach and breast cancer caused by an inherited mutation in the CDH1 gene.
Q. How is the mutation detected?
A. By a blood test.
Q. What has the study found?
A. It has produced precise risk estimates of developing the disease if a person has one of the mutations.
Q. Why is this important?
A. It gives patients with the inherited mutation a better basis for deciding whether to have their stomach removed preventively, or instead have annual cancer check-ups.