Table 1.
Distribution of demographic and tumor characteristics among case subjects with breast cancer and control subjects*
| Characteristic | Control subjects, n (%) | Case subjects, n (%) |
|
| ER+ | Triple negative | ||
| Stage | |||
| Localized | N/A | 1910 (74) | 213 (71) |
| Regional or distant | 664 (26) | 89 (29) | |
| Unknown | 36 | 5 | |
| Tumor grade | |||
| Well differentiated | N/A | 772 (32) | 15 (5) |
| Moderately differentiated | 1097 (46) | 55 (19) | |
| Poorly differentiated or anaplastic | 509 (21) | 221 (76) | |
| Unknown | 232 | 16 | |
| Tumor size, mm | |||
| <10 | N/A | 733 (31) | 49 (18) |
| 10–19 | 1007 (43) | 123 (44) | |
| 20–39 | 494 (21) | 77 (28) | |
| ≥40 | 117 (5) | 30 (11) | |
| Unknown | 260 | 28 | |
| Age at random assignment or enrollment, y | |||
| 50–59 | 50 400 (34) | 746 (29) | 122 (40) |
| 60–69 | 67 505 (45) | 1250 (48) | 125 (41) |
| 70–79 | 32 624 (22) | 614 (24) | 60 (20) |
| Race and/or ethnicity | |||
| Non-Hispanic white | 124 008 (86) | 2317 (92) | 241 (81) |
| Hispanic or Latina | 6084 (4) | 53 (2) | 8 (3) |
| African American | 13 675 (10) | 149 (6) | 50 (17) |
| Other or unknown | 6762 | 91 | 8 |
| Education | |||
| ≤High school diploma or GED | 33 928 (23) | 483 (19) | 75 (25) |
| Vocational or training school | 15 347 (10) | 232 (9) | 30 (10) |
| Some college or associate’s degree | 41 508 (28) | 696 (27) | 78 (26) |
| ≥College graduate | 58 622 (39) | 1177 (45) | 118 (39) |
| Missing | 1124 | 22 | 6 |
| Breast cancer family history | |||
| No | 116 663 (82) | 1901 (77) | 207 (72) |
| Yes | 25 648 (18) | 574 (23) | 81 (28) |
| Unknown | 8218 | 135 | 19 |
| Menopausal hormone therapy use | |||
| Never use | 56 534 (38) | 841 (32) | 114 (37) |
| Exclusive use of unopposed estrogen | 47 871 (32) | 727 (28) | 106 (35) |
| Ever use of combined estrogen–progestin | 46 101 (31) | 1042 (40) | 87 (28) |
| Unknown | 23 | 0 | 0 |
| Smoking history | |||
| Never | 75 933 (51) | 1227 (48) | 158 (52) |
| Ever | 72 648 (49) | 1350 (52) | 147 (48) |
| Unknown | 1948 | 33 | 2 |
| BMI at baseline, kg/m2 | |||
| <23.75 | 37 377 (25) | 596 (23) | 66 (22) |
| 23.75–26.89 | 37 318 (25) | 650 (25) | 71 (23) |
| 26.90–31.04 | 37 326 (25) | 648 (25) | 80 (26) |
| ≥31.05 | 37 207 (25) | 698 (27) | 89 (29) |
| Unknown | 1301 | 18 | 1 |
*
GED = General Educational Development; BMI = body mass index; ER+ = estrogen receptor–positive with known HER2 status; triple negative = ER−, PR−, and HER2−.