A national screening programme for prostate cancer could be introduced by the NHS following an international effort by more than 1,000 scientists to unravel the genetic causes of prostate, breast and ovarian cancer.
The study, the largest to look for the faulty DNA that drives the cancers, revealed scores of genetic markers that can identify people most likely to develop the diseases.
Doctors said a simple £5 saliva test based on the markers could give patients a personalised "risk profile" for the diseases and pave the way for individually tailored screening, with those most at risk having more regular health checks.
The findings have major implications for the treatment of prostate cancer. A test based on markers for the disease could identify men whose lifetime risk was 50%, nearly five times the national average.
Ros Eeles, professor of cancer genetics at the Institute of Cancer Research in London, described the results as "the single biggest leap forward" in understanding the genetics of the disease.
