title: Effectiveness of Breast Cancer Screening: Systematic Review and Meta-analysis to Update the 2009 U.S. Preventive Services Task Force Recommendation.
abstract: BACKGROUND
  In 2009, the U.S. Preventive Services Task Force recommended biennial mammography screening for women aged 50 to 74 years and selective screening for those aged 40 to 49 years.
  
  
  OBJECTIVE
  To review studies of the effectiveness of breast cancer screening in average-risk women.
  
  
  METHODS
  MEDLINE and Cochrane databases to 4 June 2015.
  
  
  METHODS
  English-language randomized, controlled trials and observational studies of screening with mammography, magnetic resonance imaging, and ultrasonography that reported breast cancer mortality, all-cause mortality, or advanced breast cancer outcomes.
  
  
  METHODS
  Investigators extracted and confirmed data and dual rated study quality; discrepancies were resolved through consensus.
  
  
  RESULTS
  Fair-quality evidence from a meta-analysis of mammography trials indicated relative risks (RRs) for breast cancer mortality of 0.92 for women aged 39 to 49 years (95% CI, 0.75 to 1.02) (9 trials; 3 deaths prevented per 10,000 women over 10 years); 0.86 for those aged 50 to 59 years (CI, 0.68 to 0.97) (7 trials; 8 deaths prevented per 10,000 women over 10 years); 0.67 for those aged 60 to 69 years (CI, 0.54 to 0.83) (5 trials; 21 deaths prevented per 10,000 women over 10 years); and 0.80 for those aged 70 to 74 years (CI, 0.51 to 1.28) (3 trials; 13 deaths prevented per 10,000 women over 10 years). Risk reduction was 25% to 31% for women aged 50 to 69 years in observational studies of mammography screening. All-cause mortality was not reduced with screening. Advanced breast cancer was reduced for women aged 50 years or older (RR, 0.62 [CI, 0.46 to 0.83]) (3 trials) but not those aged 39 to 49 years (RR, 0.98 [CI, 0.74 to 1.37]) (4 trials); less evidence supported this outcome.
  
  
  CONCLUSIONS
  Most trials used imaging technologies and treatments that are now outdated, and definitions of advanced breast cancer were heterogeneous. Studies of effectiveness based on risk factors, intervals, or other modalities were unavailable or methodologically limited.
  
  
  CONCLUSIONS
  Breast cancer mortality is generally reduced with mammography screening, although estimates are not statistically significant at all ages and the magnitudes of effect are small. Advanced cancer is reduced with screening for women aged 50 years or older.
  
  
  BACKGROUND
  Agency for Healthcare Research and Quality.
authors.forename: Heidi D
authors.initials: HD
authors.lastname: Nelson
authors.forename: Rochelle
authors.initials: R
authors.lastname: Fu
authors.forename: Amy
authors.initials: A
authors.lastname: Cantor
authors.forename: Miranda
authors.initials: M
authors.lastname: Pappas
authors.forename: Monica
authors.initials: M
authors.lastname: Daeges
authors.forename: Linda
authors.initials: L
authors.lastname: Humphrey
mesh_terms: D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000401:mortality* / Q000517:prevention & control*; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D012307:Risk Factors; D013997:Time Factors