Table 1.
Characteristics of 705 Cases (women with contralateral breast cancer) and 1,398 Controls (women with unilateral breast cancer only)
| Characteristic | Cases (n = 705) |
Controls (n = 1,398) |
||
|---|---|---|---|---|
| No. | % | No. | % | |
| Age at diagnosis, years | ||||
| < 30 | 8 | 1.1 | 16 | 1.1 |
| 30-34 | 40 | 5.7 | 74 | 5.3 |
| 35-39 | 91 | 12.9 | 179 | 12.8 |
| 40-44 | 170 | 24.1 | 338 | 24.2 |
| 45-49 | 205 | 29.1 | 407 | 29.1 |
| 50-54 | 191 | 27.1 | 384 | 27.5 |
| Median | 46 | 46 | ||
| Range (interquartile) | 41-51 | 42-50 | ||
| At-risk period, years* | ||||
| < 5 | 405 | 57.4 | 807 | 58.3 |
| ≥ 5 | 300 | 42.6 | 591 | 41.7 |
| Race/ethnicity | ||||
| Non-Hispanic white | 646 | 91.6 | 1,287 | 92.1 |
| Hispanic white | 24 | 3.4 | 48 | 3.4 |
| Black | 21 | 3.0 | 39 | 2.8 |
| Japanese | 2 | 0.3 | 4 | 0.3 |
| Chinese | 2 | 0.3 | 3 | 0.2 |
| Filipino | 7 | 1.0 | 14 | 1.0 |
| Other Asian/other | 3 | 0.4 | 3 | 0.2 |
| Jewish ancestry | ||||
| No | 637 | 90.4 | 1,272 | 92.7 |
| Yes | 54 | 7.7 | 108 | 6.1 |
| Unknown | 14 | 2.0 | 18 | 1.2 |
| Family history of breast cancer | ||||
| No first-degree relative | 475 | 67.4 | 1,098 | 78.8 |
| Any first-degree relative | 226 | 32.1 | 289 | 20.5 |
| Adopted or unknown | 4 | 0.6 | 11 | 0.7 |
| Family history of ovarian cancer | ||||
| No first-degree relative | 676 | 95.9 | 1,338 | 95.6 |
| Any first-degree relative | 25 | 3.5 | 49 | 3.6 |
| Adopted or unknown | 4 | 0.6 | 11 | 0.7 |
| Center | ||||
| Iowa | 113 | 16.0 | 222 | 15.9 |
| University of California at Irvine | 118 | 16.7 | 231 | 16.5 |
| Los Angeles | 199 | 28.2 | 390 | 27.9 |
| Seattle | 99 | 14.0 | 198 | 14.2 |
| Denmark | 176 | 25.0 | 357 | 25.5 |
| Menopausal status | ||||
| Premenopausal | 124 | 17.6 | 272 | 18.4 |
| Postmenopausal, < 45 years | 208 | 29.5 | 455 | 34.5 |
| Postmenopausal, ≥ 45 years | 372 | 52.8 | 665 | 46.5 |
| Unknown | 1 | 0.1 | 6 | 0.6 |
| Estrogen receptor status of first primary breast cancer | ||||
| Positive | 336 | 47.7 | 745 | 53.9 |
| Negative | 193 | 27.4 | 338 | 23.6 |
| Other | 69 | 9.8 | 155 | 11.9 |
| Unknown | 107 | 15.2 | 160 | 10.6 |
| Chemotherapy for first primary breast cancer | ||||
| No | 384 | 54.5 | 628 | 42.5 |
| Yes | 321 | 45.5 | 770 | 57.5 |
| Adjuvant hormone therapy for first primary breast cancer | ||||
| No | 530 | 75.2 | 969 | 70.2 |
| Yes | 163 | 23.1 | 399 | 27.5 |
| Unknown | 12 | 1.7 | 30 | 2.3 |
| Radiation therapy | ||||
| No | 361 | 51.2 | 266 | 50.1 |
| Yes | 344 | 48.8 | 1,132 | 49.9 |
| Oophorectomy status | ||||
| Yes | 47 | 6.7 | 123 | 8.4 |
| No | 657 | 93.2 | 1,273 | 91.6 |
| Unknown | 1 | 0.1 | 2 | 0.1 |
NOTE. Proportions are weighted for the counter-matching with the exception of factors contributing to the study matching schema (age, race/ethnicity, and center).
*
Interval between first diagnosis and second diagnosis (cases) or reference date (controls).