Eight RCTs (n=556,907) were included in the meta-analysis. All trials were judged to be fair quality.
Pooled results showed a a statistically significant reduced risk for breast cancer mortality for women aged 40 to 49 years who received mammography screening (RR 0.85, 95% CI 0.75 to 0.96), which indicated a 15% reduction in outcome following screening. The number needed to screen to prevent one breast cancer death was 1,904 (95% CI 929 to 6,378) over screening rounds that varied between two and nine, and over an 11 to 20 year follow-up period. There was no evidence of publication bias or heterogeneity. Sensitivity analyses did not significantly alter the results.
Statistically significant results were reported for women aged 50 to 59 years (RR 0.86, 95% CI 0.75 to 0.99, number needed to screen 1,339; six trials) and those aged 60 to 69 years (RR 0.68, 95% CI 0.54 to 0.87, number needed to screen 377; two trials). Evidence in women aged 70 years or older was limited to one trial and the relative risk was not statistically significant.
Results for mortality associated with clinical breast examination and harms of clinical breast examination and breast self examination screening were inconclusive.