Table 6

RRsa of breast cancer in relation to percent density, Wolfe classification, and types of calcifications on screening mammograms by time since screening mammogram

Time since mammogram
1 to <3 years3 to <6 years≥6 years
CasesControlsRR (95% CI)CasesControlsRR (95% CI)CasesControlsRR (95% CI)
Percent density
 ≤26.78441.0 (reference)27491.0 (reference)18251.0 (reference)
 26.8–50.131523.2 (1.4–8.2)43461.7 (0.9–3.2)18201.4 (0.6–3.5)
 50.2–70.261496.8 (3.0–17)69363.9 (2.1–7.5)46332.3 (1.1–5.3)
 ≥70.3723512.6 (5.5–32)89503.4 (1.9–6.3)65332.9 (1.4–6.3)
Wolfe classification
 N1 and P110581.0 (reference)33611.0 (reference)21271.0 (reference)
 P21491167.9 (4.0–17)1691103.1 (1.9–5.1)102761.9 (1.0–3.9)
 DY13612.1 (3.9–43)26104.9 (2.2–12)2483.9 (1.4–11)
Calcification classification
 None49961.0 (reference)80841.0 (reference)63491.0 (reference)
 Class 57120.4 (0.1–1.2)13160.5 (0.2–1.2)1151.7 (0.6–5.7)
 Class 485552.2 (1.4–3.5)90621.3 (0.8–2.0)53490.7 (0.4–1.2)
 Class 347341.2 (0.7–2.1)56391.0 (0.6–1.7)30141.9 (0.9–4.0)
 Class 239231.8 (1.0–3.4)45182.2 (1.2–4.3)27141.5 (0.7–3.1)
 Class 11552.9 (1.0–9.5)1419.8 (1.9–179)522.9 (0.6–22)
  • a Adjusted for age and study. RRs in relation to each class of calcification are also adjusted for other types of calcifications.