Screening women aged 50 to 69 for breast cancer does save lives, according to the World Health Organisation. However, there has been a big debate recently about whether mammography is worthwhile since Danish researchers question the validity of studies suggesting that it is effective. Now the internal Agency for Research on Cancer has reviewed the scientific evidence. They have concluded that screening reduces the death rate by 4 in 10,000. It is difficult though since some women screened can subsequently undergo treatment for disease which, whilst detectable on screening, would never have caused symptoms during her lifetime. Furthermore, the X-rays used to carry out a mammogram can themselves produce cancers in a tiny proportion of those exposed.