Studies Included	Comments	Conclusions
All RCTs*	Much less data to answer question in women aged 40 to 49 years as most trials were in women aged over 50. Best available data show no significant reduction in breast cancer mortality in women aged under 50 years. In the absence of convincing data on efficacy, harmful effects may outweigh any positive effects.	Trial data to date do not provide scientific justification to recommend screening for women younger than 50. This conclusion does not exclude possibility that screening of individual women, based on a personalized risk assessment, could be of benefit. These conclusions should be reviewed when results from the UK Age Trial become available.

^*RCT indicates randomized controlled trial.