Updated results of the trials of screening mammography

Most analysts agree that screening women for breast cancer can reduce the death rate by at least 25% to 30%. In 1993 the National Cancer Institute created a great deal of confusion among women and their physicians by withdrawing support for screening women aged 40 to 49 years. The controversy arose as a result of the inappropriate and scientifically insupportable analysis of data from the early results from the randomized controlled trials of screening. Despite that the trials were not designed to evaluate women aged 40 to 49 years as a separate subgroup and that they lacked the statistical power to permit legitimate analysis of this subgroup, women aged 40 to 49 years were analyzed separately, and erroneous conclusions were drawn. In an effort to justify these conclusions, other data have been analyzed improperly to try to suggest that significant screening parameters change at menopause or at the age of 50, whereas the facts do not support any abrupt change. There are no parameters such as breast density, cancer detection rate, or positive predictive value that change abruptly at age 50 or any other age. With longer follow-up of the screening trial data and the commensurately greater statistical power, the most recent meta-analyses provide statistically significant proof that screening can reduce the death rate from breast cancer for women aged 40 to 49 years by at least 24%.