Table 1.
Variable | Median (range) | Cases (CBC) median (range) | Controls (UBC) median (range) |
---|---|---|---|
Age at first diagnosis (years) | 45 (23–55) | 44 (24–55) | 45 (23–55) |
Age at reference date (years) | 49 (27–71) | 49 (27–71) | 49 (27–69) |
Length of at-risk perioda (years) | 4.2 (1.0–15.6) | 4.2 (1.0–15.6) | 4.3 (1.0–15.6) |
Variable | Level | Cases (CBC) |
Controls (UBC) |
||
---|---|---|---|---|---|
N | % | N | % | ||
Center | Iowa | 83 | 16.2 | 162 | 16.2 |
UC Irvine | 86 | 16.8 | 148 | 14.8 | |
Los Angeles | 145 | 28.4 | 277 | 27.7 | |
Seattle | 65 | 12.7 | 133 | 13.3 | |
Denmark | 132 | 25.8 | 279 | 27.9 | |
Year at first diagnosis | 1985–1988 | 183 | 35.8 | 345 | 34.5 |
1989–1992 | 176 | 34.4 | 355 | 35.5 | |
1993–1996 | 122 | 23.9 | 237 | 23.7 | |
1997+ | 30 | 5.9 | 62 | 6.2 | |
Chemotherapy | No | 253 | 49.5 | 416 | 41.6 |
Yes | 258 | 50.5 | 583 | 58.4 | |
Hormone treatmentb | No | 382 | 74.8 | 686 | 68.7 |
Yes | 129 | 25.2 | 312 | 31.2 | |
Unknown | 0 | 0 | 1 | 0.1 | |
Radiation treatment | Never | 266 | 52.1 | 187 | 18.7 |
Ever | 245 | 47.9 | 812 | 81.3 | |
Histology of first breast cancer | Lobular | 61 | 11.9 | 92 | 9.2 |
Other | 450 | 88.1 | 907 | 90.8 | |
Stage of first breast cancer | Localized | 355 | 69.5 | 631 | 63.2 |
Regional | 156 | 30.5 | 368 | 36.8 | |
ER Status of first breast cancerc | Positive | 244 | 47.7 | 509 | 51 |
Negative | 139 | 27.2 | 252 | 25.2 | |
Other | 128 | 25 | 238 | 23.8 | |
PR Status of first breast cancerc | Positive | 211 | 41.3 | 423 | 42.3 |
Negative | 120 | 23.5 | 232 | 23.2 | |
Other | 180 | 35.2 | 344 | 34.4 | |
Age at menarche (years) | 8–13 | 239 | 46.8 | 435 | 43.5 |
13–19 | 272 | 53.2 | 564 | 56.5 | |
Number of full-term pregnancies | None | 102 | 20 | 170 | 17 |
1–3 | 375 | 73.4 | 729 | 73 | |
4–14 | 34 | 6.7 | 100 | 10 | |
Menopausal status/age at menopause at start of at-risk periodd | Premenopausal | 247 | 48.3 | 411 | 41.1 |
Postmenopausal age <45 | 109 | 21.3 | 249 | 24.9 | |
Postmenopausal age 45+ | 155 | 30.3 | 339 | 33.9 | |
Unknown | 0 | 0 | 0 | 0 | |
Family history of breast cancer | None | 342 | 66.9 | 781 | 78.2 |
1+ | 161 | 31.5 | 201 | 20.1 | |
Adopted | 8 | 1.6 | 17 | 1.7 |
Excludes women with missing height and/or weight (n = 21), those who were outliers for BMI (n = 44) or weight (n = 4) at either age 18, first diagnosis or reference date, women who reported use of postmenopausal hormone therapy at any time prior to reference date (n = 525) and women with missing information on menopausal status (n = 3). This left 511 CBC cases and 999 UBC controls for this analysis
CBC asynchronous contralateral breast cancer, UBC unilateral breast cancer, ER estrogen receptor, PR progesterone receptor
Beginning 1 year after first diagnosis extending to the reference date (date of second diagnosis in cases)
Hormone therapy includes all hormonal breast cancer treatments including: tamoxifen, raloxifene, toremifene citrate, anastrozole, letrozole, exemestane, aminoglutethimide, goserelin acetate, leuprorelin, fulvestrant and megestrol acetate
Refers to receptor status of the first primary breast cancer. The ‘Other’ category consists of women where no lab test was given, the test was given and the results are unknown or the test was given and the results were borderline
Defined as menopausal status as of 1 year after first diagnosis (the start of the at-risk period). If a woman reported that she was still menstruating up to 1 year after first diagnosis or was pregnant, she was classified as premenopausal