Table 1.
Characteristics of CBC cases and UBC controls and those treated and not treated with tamoxifen from the WECARE Study population who were also screened for CYP2D6 variants
| Variable | CBC cases (N = 1514) | UBC controls (N = 2203) | Tamoxifen treatment (N = 1250) | No tamoxifen treatment (N = 2467) |
|---|---|---|---|---|
| Age at first diagnosis (years), median (range) | 46 (24–54) | 48 (24–54) | 48 (24–54) | 45 (23–54) |
| Age at reference date (years), median (range) | 53 (27–73) | 54 (28–73) | 54 (28–73) | 51 (27–71) |
| Length of at-risk period (years)a, median (range) | 6.3 (1.0–19.8) | 6.0 (1.0–19.3) | 6.0 (1.0–19.3) | 5.8 (1.0–19.8) |
| Study area, N (%) | ||||
| Iowab | 201 (13) | 314 (14) | 170 (14) | 345 (14) |
| Californiac | 655 (43) | 963 (44) | 634 (51) | 984 (40) |
| Seattled | 223 (15) | 317 (14) | 249 (20) | 291 (12) |
| Denmarke | 279 (18) | 452 (21) | 57 (5) | 674 (27) |
| Canadaf | 156 (10) | 157 (7) | 140 (11) | 173 (7) |
| Year of first breast cancer diagnosis, N (%) | ||||
| 1985–1988 | 238 (16) | 466 (21) | 122 (10) | 582 (24) |
| 1989–1992 | 414 (27) | 643 (29) | 328 (26) | 729 (30) |
| 1993–1996 | 425 (28) | 630 (29) | 353 (28) | 702 (28) |
| 1997–2008 | 437 (29) | 464 (21) | 447 (36) | 454 (18) |
| Race/ethnicityg, N (%) | ||||
| Non-Hispanic white | 1330 (88) | 1971 (89) | 1070 (86) | 2231 (90) |
| Hispanic white | 68 (4) | 93 (4) | 59 (5) | 102 (4) |
| Black | 54 (4) | 75 (3) | 47 (4) | 82 (3) |
| Asian | 45 (3) | 52 (2) | 61 (5) | 36 (1) |
| Other | 17 (1) | 12 (1) | 13 (1) | 16 (1) |
| Age at menarche (years), N (%) | ||||
| Never had menses | 3 (0) | 6 (0) | 1 (0) | 8 (0) |
| < 13 | 722 (48) | 962 (44) | 622 (50) | 1062 (43) |
| ≥ 13 | 786 (52) | 1233 (56) | 625 (50) | 1394 (57) |
| Unknown | 3 (0) | 2 (0) | 2 (0) | 3 (0) |
| Number of full-term pregnancies, N (%) | ||||
| None | 320 (21) | 408 (19) | 246 (20) | 482 (20) |
| 1 | 271 (18) | 340 (15) | 200 (16) | 411 (17) |
| 2 | 556 (37) | 839 (38) | 444 (36) | 951 (39) |
| 3 | 255 (17) | 386 (18) | 237 (19) | 404 (16) |
| ≥ 4 | 107 (7) | 225 (10) | 118 (9) | 214 (9) |
| Unknown | 5 (0) | 5 (0) | 5 (0) | 5 (0) |
| Menopausal status at first diagnosish, N (%) | ||||
| Premenopausal | 1119 (74) | 1669 (76) | 865 (69) | 1923 (78) |
| Postmenopausal | 387 (26) | 520 (24) | 377 (30) | 530 (21) |
| Unknown | 8 (1) | 14 (1) | 8 (1) | 14 (1) |
| First-degree family history of breast cancer, N (%) | ||||
| No | 999 (66) | 1697 (77) | 901 (72) | 1795 (73) |
| Yes | 496 (33) | 466 (21) | 325 (26) | 637 (26) |
| Adopted/unknown | 19 (1) | 40 (2) | 24 (2) | 35 (1) |
| Stage of first primary breast cancer, N (%) | ||||
| Local | 1059 (70) | 1436 (65) | 747 (60) | 1748 (71) |
| Regional | 446 (29) | 756 (34) | 493 (39) | 709 (29) |
| Unknown | 9 (1) | 11 (1) | 10 (1) | 10 (0) |
| Histology of first diagnosis, N (%) | ||||
| Nonlobular | 1334 (88) | 1978 (90) | 1061 (85) | 2251 (91) |
| Lobular | 179 (12) | 222 (10) | 186 (15) | 215 (9) |
| Unknown | 1 (0) | 3 (0) | 3 (0) | 1 (0) |
| ER status of first diagnosis, N (%) | ||||
| Positive | 793 (52) | 1248 (57) | 1047 (84) | 994 (40) |
| Negative | 467 (31) | 560 (25) | 129 (10) | 898 (36) |
| Other/unknowni | 254 (17) | 395 (18) | 74 (6) | 575 (23) |
| Chemotherapy for first diagnosis, N (%) | ||||
| No | 696 (46) | 919 (42) | 485 (39) | 1130 (46) |
| Yes | 818 (54) | 1284 (58) | 765 (61) | 1337 (54) |
| Radiation treatment for first diagnosisj, N (%) | ||||
| WECARE I | ||||
| No | 362 (51) | 265 (50) | 139 (25) | 488 (32) |
| Yes | 346 (49) | 1130 (50) | 424 (75) | 1052 (68) |
| Unknown | 0 (0) | 0 (0) | 0 (0) | 0 (0) |
| WECARE II | ||||
| No | 275 (34) | 258 (32) | 195 (28) | 338 (36) |
| Yes | 531 (66) | 549 (68) | 491 (71) | 589 (64) |
| Unknown | 0 (0) | 1 (0) | 1 (0) | 0 (0) |
| Hormone treatment for first diagnosis, N (%) | ||||
| None | 960 (63) | 1263 (57) | NA | NA |
| Tamoxifen | 465 (31) | 785 (36) | ||
| Other hormonal treatmentk | 89 (6) | 153 (7) | ||
| Unknown | 0 (0) | 2 (0) | ||
CBC contralateral breast cancer, UBC unilateral breast cancer, WECARE Women’s Environmental Cancer and Radiation Epidemiology, ER estrogen receptor, NA not available
aBeginning at least 1 year after first diagnosis and extending to the date of CBC diagnosis of cases
bThe State Health Registry of Iowa
cFour study centers: Los Angeles County Cancer Surveillance Program; The Cancer Surveillance Program of Orange County/San Diego-Imperial Organization for Cancer Control; Greater Bay Area Cancer Registry (San Francisco Bay Area Region and Santa Clara Region); and Sacramento and Sierra Center Registries (Sacramento Region)
dCancer Surveillance System of the Fred Hutchinson Cancer Research Center
eThe Danish Breast Cancer Cooperative Group Database supplemented by the Danish Cancer Registry
fThe Ontario Cancer Registry
g‘Asian’ includes Japanese, Chinese, and Filipino; ‘Other’ includes other Asian as well as all other races/ethnicities
hWomen were classified as premenopausal if they reported having menstrual periods or being pregnant within 2 years of initial diagnosis
i‘Other/unknown’ category consists of women where no laboratory test was given, the test was given and the results are unknown, or the test was given and the results were borderline; estimates not reported. Start date for ER reporting in Surveillance Epidemiology and End Results was January 1, 1990
jProportion of individuals treated and not treated with radiation. In WECARE 1, cases and controls were counter-matched based on cancer registry reported radiation treatment such that two members of each case–control trio had received radiation treatment for their first breast cancer diagnosis. Proportions for controls in WECARE 1 are weighted to reflect this selection. Proportions for cases in WECARE 1 (because all cases were included) and both cases and controls in WECARE II (because counter-matching was not used in WECARE II) are not weighted
kOther hormonal therapies include: raloxifene/Evista, tormifene/Fareston, anastrozole/Arimidex, letrozole/Femara, aromasin/Exemestane, aminoglutethimide/Cytradren, gosereline/Zoladex, leuprolide/Lupron, faslodex/Fulvestrant, and megestrol acetate/Megace