MedicalResearch.com Interview with: Anthony Miller, MD Director, Canadian National Breast Screening Study Professor Emeritus, Dalla Lana School of Public Health University of Toronto MedicalResearch.com: What are the main findings of the study? Prof. Miller:  The study involved 89,835 women aged 40 to 59. All underwent an annual physical breast examination, while half were randomly assigned to undergo annual mammograms for five years, beginning in 1980. During the five-year screening period, 666 invasive breast cancers were diagnosed in the mammography arm and 524 in the controls.  Over the 25 year follow-up 180 women in the mammography arm and 171 women in the control arm died of breast cancer.  The overall hazard ratio for death from breast cancer diagnosed during the screening period associated with mammography was 1.05 (95% CI: 0.85 – 1.30).  The findings for women aged 40-49 and aged 50-59 were almost identical. After 15 years of follow-up an excess of 106 cancers was observed in the mammography arm, attributable to over-diagnosis, i.e. 22% of screen-detected invasive breast cancers, half of those detected by mammography alone. This represents one over-diagnosed breast cancer for every 424 women screened by mammography. By 2005, 3,250 of the 44,925 women in the mammography arm of the study were diagnosed with breast cancer, and 500 had died of it. The control group of 44,910 women had 3,133 breast cancer diagnoses and 505 breast cancer deaths. We conclude that annual mammography in women aged 40-59 does not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available. (more…)