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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

From: CYP2D6 phenotype, tamoxifen, and risk of contralateral breast cancer in the WECARE Study

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)   
  1. CBC contralateral breast cancer, UBC unilateral breast cancer, WECARE Women’s Environmental Cancer and Radiation Epidemiology, ER estrogen receptor, NA not available
  2. aBeginning at least 1 year after first diagnosis and extending to the date of CBC diagnosis of cases
  3. bThe State Health Registry of Iowa
  4. 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)
  5. dCancer Surveillance System of the Fred Hutchinson Cancer Research Center
  6. eThe Danish Breast Cancer Cooperative Group Database supplemented by the Danish Cancer Registry
  7. fThe Ontario Cancer Registry
  8. g‘Asian’ includes Japanese, Chinese, and Filipino; ‘Other’ includes other Asian as well as all other races/ethnicities
  9. hWomen were classified as premenopausal if they reported having menstrual periods or being pregnant within 2 years of initial diagnosis
  10. 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
  11. 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
  12. 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