Tamoxifen, the so called "statin of breast cancer prevention" is recommended for healthy women with a family history of the disease. So why are only 1 in 7 of those eligible taking it? And Mark Porter speaks to Professor Gareth Evans working with his team at the Wythenshawe Hospital in Manchester to reliably identify women at higher risk of breast cancer. They are testing for SNPS, spelling mistakes in the DNA that influence growth and survival of cancer cells and that give a more accurate assessment of a woman's risk.