Background: Eight randomized controlled trials (RCTs) of screening mammography were conducted involving women ages 40 to 49 years at entry. Current data gathered for periods ranging from 7 to 18 years of follow-up are available from these trials.
Methods: Meta-analyses were performed using a Mantel-Haenszel estimator method to combine current follow-up data from the eight RCTs of mammography that included women ages 40 to 49 years.
Results: Combining all current data on women ages 40 to 49 years at entry into the trials yielded a 16% [corrected] benefit from screening mammography, without statistical significance at the 95% confidence level. Combining all data on women ages 40 to 49 years at entry, excluding results from the Canadian National Breast Screening Study, yielded a 24% [corrected] benefit to women invited for screening, with statistical significance at the 95% confidence level.
Conclusions: These results suggest that screening mammography in women ages 40 to 49 years at entry can reduce mortality from breast cancer when combined with adequate follow-up.