Table 2 Association between mammographic density and other selected risk factors, and risk of total, invasive, and in situ breast cancer in the NBCSP case-control study
Total breast cancer | Invasive breast cancer | Ductal carcinoma in situ | |||||||
|---|---|---|---|---|---|---|---|---|---|
Baseline risk factor | No. of controls (%) | No. of cases (%) | Odds ratioa (95% CI) | No. of cases (%) | Odds ratioa (95% CI) | No. of cases (%) | Odds ratioa (95% CI) | ||
Age at first live birthb | |||||||||
5-year increase | 4,048 (86.8) | 940 (81.3) | 1.12 (1.02-1.22) | 795 (81.8) | 1.10 (1.00-1.21) | 145 (78.8) | 1.19 (0.97-1.46) | ||
Nulliparous | 618 (13.2) | 216 (18.7) | 1.34 (1.12-1.61) | 177 (18.2) | 1.30 (1.06-1.58) | 39 (21.2) | 1.58 (1.04-2.40) | ||
Age at menopausec | |||||||||
5-year increase | 3,040 (65.2) | 728 (63.0) | 1.18 (1.06-1.30) | 619 (63.7) | 1.17 (1.05-1.30) | 109 (59.2) | 1.20 (0.92-1.55) | ||
Premenopausal | 1,626 (34.8) | 428 (37.0) | 1.14 (0.93-1.41) | 353 (36.3) | 1.20 (0.95-1.51) | 75 (40.8) | 0.96 (0.59-1.55) | ||
Family history of breast cancer | |||||||||
None | 4,055 (86.9) | 932 (80.6) | 1.00 (reference) | 790 (81.3) | 1.00 (reference) | 142 (77.2) | 1.00 (reference) | ||
Second-degree relative | 325 (7.0) | 107 (9.3) | 1.39 (1.10-1.75) | 89 (9.2) | 1.39 (1.08-1.79) | 18 (9.8) | 1.42 (0.83-2.43) | ||
First-degree relative ≥50 years | 172 (3.7) | 64 (5.5) | 1.46 (1.08-1.98) | 49 (5.0) | 1.33 (0.95-1.87) | 15 (8.2) | 2.11 (1.13-3.94) | ||
First-degree relative <50 years | 114 (2.4) | 53 (4.6) | 1.90 (1.35-2.68) | 44 (4.5) | 2.00 (1.38-2.91) | 9 (4.9) | 1.63 (0.77-3.47) | ||
Previous breast biopsy | |||||||||
No | 4,263 (91.4) | 986 (85.3) | 1.00 (reference) | 826 (85.0) | 1.00 (reference) | 160 (87.0) | 1.00 (reference) | ||
Yes | 403 (8.6) | 170 (14.7) | 1.57 (1.28-1.92) | 146 (15.0) | 1.68 (1.36-2.08) | 24 (13.0) | 1.11 (0.68-1.83) | ||
Mammographic density (%) | |||||||||
0-10 | 1,710 (36.6) | 263 (22.7) | 1.00 (reference) | 233 (24.0) | 1.00 (reference) | 30 (16.3) | 1.00 (reference) | ||
11-25 | 1,136 (24.3) | 244 (21.1) | 1.43 (1.18-1.74) | 206 (21.2) | 1.39 (1.12-1.71) | 38 (20.7) | 1.65 (1.01-2.83) | ||
26-50 | 1,157 (24.8) | 375 (32.4) | 2.24 (1.85-2.71) | 319 (32.8) | 2.18 (1.78-2.68) | 56 (30.4) | 2.65 (1.60-4.40) | ||
51-75 | 528 (11.3) | 215 (18.6) | 2.76 (2.19-3.48) | 164 (16.9) | 2.38 (1.85-3.06) | 51 (27.7) | 5.60 (3.24-9.67) | ||
>75 | 135 (2.9) | 59 (5.1) | 3.06 (2.14-4.40) | 50 (5.1) | 2.95 (2.01-4.35) | 9 (4.9) | 3.47 (1.46-8.27) | ||
P value for trendd | <0.001 | <0.001 | < 0.001 | ||||||