In November, 2009, a rancorous argument about screening mammography for women aged 40-49 was touched off by the publication of updated guidelines(1), supported by a systematic literature review(2) by the US Preventive Services Task Force (USPSTF). The guidelines suggested that yearly mammographic screening for women in that age group should not be automatic, but a decision made for individual patients after discussion between the patients and their doctors. This was based on a critical review of the best available data which suggested that the benefits of screening acrue to only a few patients. 1904 women would have to start screening and continue for multiple rounds to prevent one cancer death over 11-20 years of follow-up. These benefits had to be balanced...