Table 1 Characteristics of women with contralateral breast cancer (CBC) (cases) and unilateral breast cancer (UBC) controls
CBC (n = 362) | UBC (n = 403) | |
|---|---|---|
Mean (SD) | Mean (SD) | |
Age at mammogram before/at 1st diagnosis (years) | 46 (6) | 46 (6) |
Age at mammogram after 1st diagnosis (years) | 47 (6) | 47 (6) |
Follow-up timea (years) | 7.9 (3.8) | 8.0 (4.0) |
BMI at 1st diagnosis (kg/m2) | 25.2 (5.5) | 25.2 (5.7) |
BMIb at mammogram after 1st diagnosis (kg/m2) | 25.2 (5.4) | 25.8 (5.7) |
Percent mammographic density before/at 1st diagnosis | 37.6 (18.1) | 35.8 (18.3) |
Percent mammographic density after 1st diagnosis | 31.4 (18.3) | 28.0 (16.7) |
N (%) | N (%) | |
Study center | ||
Northern California | 179 (49) | 213 (53) |
Seattle | 82 (23) | 80 (20) |
Ontario | 52 (14) | 64 (16) |
Iowa | 49 (14) | 46 (11) |
Race | ||
Non-Hispanic white | 295 (83) | 334 (81) |
Other | 67 (17) | 69 (19) |
Histologic type at 1st diagnosis | ||
Non-lobular | 321 (89) | 353 (88) |
Lobular | 41 (11) | 50 (12) |
Stage at 1st diagnosis | ||
Local | 251 (69) | 254 (63) |
Regional | 106 (29) | 143 (35) |
Missing | 5 (1) | 6 (1) |
Estrogen receptor at 1st diagnosis | ||
Positive | 213 (59) | 273 (68) |
Negative | 129 (36) | 105 (26) |
Missing | 20 (6) | 25 (6) |
Chemotherapy at 1st diagnosis | ||
Yes | 236 (65) | 272 (67) |
No | 126 (35) | 131 (33) |
Radiation at 1st diagnosis | ||
Yes | 251 (69) | 179 (69) |
No | 111 (31) | 124 (31) |
Tamoxifen at 1st diagnosis | ||
Yes | 158 (44) | 221 (55) |
No | 204 (56) | 182 (45) |
Family historyc of breast cancer | ||
Yes | 123 (34) | 89 (22) |
No | 234 (65) | 306 (76) |
Adopted/missing | 5 (1) | 8 (2) |
Age at menarche (years) | ||
<13 | 194 (54) | 193 (48) |
≥13 | 167 (46) | 209 (52) |
Missing | 1 (< 1) | 1 (< 1) |
Full-term pregnancies | ||
None | 101 (28) | 95 (24) |
1–3 | 241 (67) | 278 (69) |
≥4 | 20 (6) | 30 (7) |