Table 1

Combined relative risks for breast cancer associated with different classifications of mammographic density, study designs, and study populations from meta-analysis [3]

General population
 Symptomatic population


Incidence studies
 Prevalence studies




Classification
 Cases/Non-casesa
 RR (95% CI)
 Cases/Non-casesa
 RR (95% CI)
 Cases/Non-casesa
 RR (95% CI)
Wolfe parenchymal pattern
 2,664/23,469b

2,169/32,184b
1,857/25,394b
     N1
 181/3,613
 1.0
 557/15,731
 1.0
 428/3,318
 1.0
     P1
 525/6,682
 1.8 (1.4, 2.2)
 519/9,684
 1.3 (1.0, 1.5)
 315/5,031
 1.0 (0.77, 1.3)
     P2
 1,162/10,433
 3.1 (2.5, 3.7)
 660/4,369
 2.0 (1.3, 3.0)
 526/5,128
 1.5 (0.91, 2.4)
     DY
 246/2,309
 4.0 (2.5, 6.3)
 294/2,216
 2.4 (2.0, 3.0)
 400/4,976
 1.7 (1.0, 2.8)








Percentage mammographic density
 4,508/8,342b

2,219/4,063b
160/160b
     <5%
 1,194/1,744c
 1.0
 643/1,182c
 1.0
 35/84c
 1.0
     5%–24%
1.8 (1.5, 2.2)
1.4 (1.1, 1.8)

     25%–49%
 1,049/1,045
 2.1 (1.7, 2.6)
 589/835
 2.2 (1.8, 2.8)
 66/35
 5.5 (2.8–11)
     50%–74%
2.9 (2.5, 3.4)
 438/665
 2.9 (2.3, 3.8)
 34/23
 4.8 (2.2–11)
     75%+
 1,211/999
 4.6 (3.6, 5.9)
 190/282
 3.7 (2.7, 5.0)
 25/18
 4.3 (1.8–10)








BI-RADS
 1,992/104,663b
 Vacekand Geller [30]
 Ziv et al. [57]
 397/1,589b


     Fatty
 62/7,550
 1.0 (Ref)
 0.3 (0.2, 0.4)
 20/134
 1.0

     Scattered density
 950/52,379
 2.2 (1.6, 3.0)
 1.0 (Ref)
 216/957
 1.6 (0.9, 2.8)

     Heterogeneous density
 783/36,564
 3.0 (2.2, 4.1)
 1.3 (1.1, 1.5)
 117/407
 2.3 (1.3, 4.3)

     Extremely dense
 197/8,170
 4.0 (2.8, 5.7)
 20.1 (1.6, 2.8)
 44/91
 4.5 (1.9, 10.6)

aCases and controls from individual categories may not add to the overall number of cases and controls used in the meta-analysis since categories from individual studies did not always coincide with those presented in the meta-analysis. Only numbers of cases and controls from studies with these categories are presented and used for the calculation of prevalence. bTotal cases and noncases used in meta-analysis by McCormack and colleagues [3] for each classification and study type. cWhen possible, categories were combined to provide the maximum contribution of cases and controls from individual studies. BI-RADS, Breast Imaging Reporting and Data System; CI, confidence interval; Ref, reference; RR, relative risk.

Vachon et al. Breast Cancer Research 2007 9:217   doi:10.1186/bcr1829