Men born at high risk of developing prostate cancer should have extra checks every year from the age of 40, experts say.
Men with certain mutations in their DNA, their genetic code, are more likely to develop prostate cancer.
Scientists at the Institute of Cancer Research (ICR) said an annual blood test could help spot tumours early, when they were easier to treat.
Prostate Cancer UK said any decisions needed to be made carefully.
Read more on BBC News.