Table 2. Performance According to Breast Density Category.
| Variable | Total participants (N = 19 213) | Dense breastsa | Nondense breastsa | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Intervention group (n = 9705) | Control group (n = 9508) | P value | Intervention group (n = 5797) | Control group (n = 5593) | P value | Intervention group (n = 3908) | Control group (n = 3915) | P value | |
| Screen-detected cancers | |||||||||
| No. of cancers/total No. | 68/9705 | 38/9508 | .004 | 41/5797 | 24/5593 | .04 | 27/3908 | 14/3915 | .04 |
| No. of cancers per 1000 screenings (95% CI) | 7 (5.3 to 8.7) | 4 (2.7 to 5.3) | 7.1 (4.9 to 9.2) | 4.3 (2.6 to 6.0) | 6.9 (4.3 to 9.5) | 3.6 (1.7 to 5.4) | |||
| Interval cancers | |||||||||
| No. of cancers/total No. | 5/9705 | 19/9508 | .004 | 3/5797 | 10/5593 | .04 | 2/3908 | 9/3915 | .03 |
| No. of cancers per 1000 screenings (95% CI) | 0.5 (0.1 to 1.0) | 2.0 (1.1 to 2.9) | 0.5 (−0.1 to 1.1) | 1.8 (0.7 to 2.9) | 0.5 (−0.2 to 1.2) | 2.3 (0.8 to 3.8) | |||
| Sensitivity, % (95% CI) | 93.2 (87.4 to 99.0) | 66.7 (54.4 to 78.9) | <.001 | 93.2 (85.7 to 100) | 70.6 (55.3 to 85.9) | <.001 | 93.1 (83.9 to 102.3) | 60.9 (40.9 to 80.8) | <.001 |
| Specificity, % (95% CI) | 86.8 (86.2 to 87.5) | 91.8 (91.2 to 92.3) | <.001 | 85.4 (84.5 to 86.3) | 91.7 (91.0 to 92.4) | <.001 | 89.0 (88.0 to 90.0) | 91.9 (91.1 to 92.8) | <.001 |
a
The 2 least dense categories (almost entirely fatty and scattered fibroglandular tissues) are referred to as nondense, and the 2 most dense categories (heterogeneously dense and extremely dense) are referred to as dense.