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Table 2 Mammographic density and risk of breast cancer according to method of detection: unmatched analysis and radiologists' classification of density

From: Mammographic density and breast cancer risk: current understanding and future prospects

    Categories of percent density, percentage  
   Number of pairsa <10 10 to <25 25 to <50 50 to <75 >75 P valueb
All Case 1,112 230 272 336 178 96  
  Control 1,112 362 270 290 144 46  
  ORc   1 1.75 2.06 2.43 4.74 <0.0001
  (95% CI)    (1.4, 2.2) (1.6, 2.6) (1.8, 3.3) (3.0, 7.4)  
Screen-detected Case 717 173 171 219 102 52  
  Control 717 242 162 196 88 29  
  ORc   1 1.65 1.77 1.98 3.52 <0.0001
  (95% CI)    (1.2, 2.2) (1.3, 2.4) (1.3, 2.9) (2.0, 6.2)  
Non-screen-detected <12 monthsd Case 124 12 22 33 32 25  
  Control 124 35 29 29 23 8  
  ORc   1 2.11 3.61 5.65 17.81 <0.0001
  (95% CI)    (0.9, 5.2) (1.5, 8.7) (2.1, 15.3) (4.8, 65.9)  
Non-screen-detected >12 monthse Case 262 43 79 80 42 18  
  Control 262 82 79 62 30 9  
  ORc   1 2.00 2.64 3.13 5.68 <0.0001
  (95% CI)    (1.2, 3.4) (1.5, 4.6) (1.6, 6.2) (2.1, 15.5)  
  1. aNine pairs were excluded from the screen or non-screen group analysis because of missing information on detection (n = 1) or the last mammogram date (n = 8). bP value for the Cochran-Armitage trend test. cAdjusted for age, body mass index, age at menarche, parity, number of live births, age at first birth, menopausal status, age at menopause, hormone replacement therapy (ever/never), breast cancer in first-degree relatives (0, 1, and 2+), study (National Breast Screening Study, Ontario Breast Screening Program, and Screening Mammography Program of British Columbia), and observation time (2 years, 2 to 4 years, and greater than 4 years). dCancers detected within 12 months of the last screening date. eCancers detected 12 months or more after the last screening date. Table reproduced from [15]. CI, confidence interval; OR, odds ratio. Republished with permission from [15].