Scientists have been researching how an inherited condition called Lynch Syndrome can increase the risk of bowel, womb and other cancers.
A new DNA model will now help diagnose those at increased risk.
In the UK alone, about 16,000 people die from bowel cancer every year, and womb cancer affects about 2,000 women making it the commonest form of gynaecological cancer.
Wales has the highest rates for womb cancer in the UK.
In all those cancer cases, it is estimated that some 5% develop the diseases as a result of having Lynch Syndrome.
Patients who currently have genetic testing for Lynch Syndrome are often given an inconclusive result which leaves them unsure of whether they face a high risk of cancer.
“As a result of this research, doctors will now be able to say much more confidently whether those patients have Lynch Syndrome, and therefore whether they are at a higher risk of cancer,” said Dr Ian Frayling from Cardiff University’s Institute of Medical Genetics.
He is one of the members of the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) which organised the research.
“It will also save NHS resources and be safer because we will be able to reassure people that they are not at risk and so don’t need the extra screening,” added Dr Frayling.
“As a result of this, colleagues and the families they care for all over the UK are now benefiting, and we are working on incorporating this into the UK guidelines on testing for Lynch Syndrome.”