It's occurring to the world's health agencies that they have got it wrong when it comes to regular mammogram screening for breast cancer. Many women are asked to start screening when they are 40 - yet research is showing that it's a waste of everyone's time. Mammogram x-rays are just not sensitive enough to pick up tumour growth in women in their 40s, a new study has found. Researchers at Stanford University School of Medicine have discovered that the technology accounted for 79 per cent of all missed cancers. This is because women aged 50 and younger have denser breast tissue, which prevents a mammogram from picking up tumour growth. Once a woman reaches the age of 50, a mammogram is a more useful detection tool, but it is still unable to pick up fast-growing tumours. (Source: Journal of the National Cancer Institute, 2010; July 27: doi: 10.1093/jnci/djq271).