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Table 1 Characteristics of breast cancer patients in the WECARE I and II Study

From: Systemic therapy for breast cancer and risk of subsequent contralateral breast cancer in the WECARE Study

Characteristics CBC cases UBC controls
N (%) N (%)
Overall numbers 1521 (100) 2212 (100)
Study area   
 Iowaa 201(13) 314 (14)
 Seattleb 224 (15) 317 (14)
 Ontarioc 159 (10) 157 (7)
 Californiad 658 (43) 967 (44)
 Denmarke 279 (18) 457 (21)
Age at first breast cancer (years)   
 ≤39 268 (18) 384 (17)
 40–49 808 (53) 1180 (53)
 50–54 445 (29) 648 (29)
Age at CBC/reference date (years)   
 ≤39 100 (6) 147 (7)
 40–49 446 (29) 691 (31)
 50–59 719 (48) 1087 (49)
 ≥60 256 (17) 287 (13)
Year of diagnosis of first breast cancer   
 1985–1989 303 (20) 580 (26)
 1990–1994 572 (38) 871 (39)
 1995–1999 426 (28) 551 (25)
 2000–2004 186 (12) 190 (9)
 2005–2008 34 (2) 20 (1)
Time since first breast cancer (years)   
 1–4 586 (39) 986 (45)
 5–9 574 (38) 804 (36)
 ≥10 361 (24) 422 (19)
First-degree family history of breast cancer   
 Yes 497 (33) 466 (21)
 No 1004 (66) 1706 (77)
 Unknown 20 (1) 40 (2)
Lobular histology of first breast cancer   
 Yes 179 (12) 223 (10)
 No 1342 (88) 1989 (90)
Stage of first breast cancer   
 Local 1061 (70) 1442 (65)
 Regional 448 (29) 759 (34)
 Unknown 12 (1) 11 (1)
ER/PR status of the first breast cancer   
 Positive 863 (57) 1379 (62)
 Negative 413 (27) 473 (21)
 Unknown 245 (16) 360 (16)
Radiation for first breast cancerf   
 Yes 880 (58) 1686 (76)
 No 641 (42) 525 (24)
Chemotherapy for first breast cancer   
 Yes 822 (54) 1289 (58)
 No 699 (46) 923 (42)
Tamoxifen use for first breast cancer   
 Yes 467 (31) 787 (36)
 No 1054 (69) 1425 (64)
Other endocrine therapy for first breast cancerg   
 Yes 89 (6) 141 (6)
 No 1432 (94) 2071 (94)
  1. aThe State Health Registry of Iowa
  2. bCancer Surveillance System of the Fred Hutchinson Cancer Research Center
  3. cThe Ontario Cancer Registry
  4. dFour study centers: 1) Los Angeles County Cancer Surveillance Program, 2) The Cancer Surveillance Program of Orange County/San Diego-Imperial Organization for Cancer Control, 3) Greater Bay Area Cancer Registry (San Francisco Bay Area Region and Santa Clara Region), and 4) Sacramento and Sierra Center Registry (Sacramento Region)
  5. eThe Danish Breast Cancer Cooperative Group Database supplemented by the Danish Cancer Registry
  6. fRadiation for first breast cancer was unknown for one control
  7. gAromatase inhibitors (67 cases and 99 controls) and other anti-estrogens
  8. CBC contralateral breast cancer, ER/PR estrogen receptor/progesterone receptor (if either ER or PR was positive, we considered the ER/PR status as positive), UBC unilateral breast cancer