Benefit of Screening Mammography in Women Aged 40-49: A New Meta-Analysis of Randomized Controlled Trials

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Abstract
Eight randomized controlled trials (RCTs) of screening mammography have been conducted involving women aged 40-49 at entry. Current data are now available from these trials at 10.5 to 18 years of follow-up (average follow-up time: 12.7 years). Meta-analysis has been performed using a Mantel-Haenszel estimator method to combine current follow-up data from the eight RCTs of mammography that included women aged 40-49 at entry, including new follow-up data presented at the NIH Consensus Development Conference held January 21-23, 1997. Combining the most recent follow-up data on women aged 40-49 at entry into all eight RCTs yields a statistically significant 18% mortality reduction among women invited to screening mammography (relative risk: 0.82; 95% confidence interval: 0.71-0.95). Combining all current follow-up data on women aged 40-49 at entry into the five Swedish RCTs yields a statistically significant 29% mortality reduction among women invited to screening (relative risk: 0.71; 95% confidence interval: 0.57-0.89). Meta-analysis including the most recent follow-up data from all eight RCTs involving women aged 40-49 at entry demonstrates for the first time a statistically significant mortality reduction due to regular screening mammography in women of this age group.