Table 1 Characteristics of contralateral breast cancer (CBC) cases and unilateral breast cancer (UBC) controls from the WECARE Study population
Variable | CBC cases NÂ =Â 1521 | UBC controls NÂ =Â 2212 | ||
|---|---|---|---|---|
Median | Range | Median | Range | |
Age at first diagnosis (years) | 46 | 24–55 | 46 | 23–55 |
Age at reference date (years) | 53 | 27–73 | 52 | 27–71 |
Length of at-risk period (years)a | 6.3 | 1.0–19.8 | 5.5 | 1.0–19.8 |
| Â | N (%) | N (%) | ||
Study center | ||||
 Iowa | 201 (13) | 314 (14) | ||
 California sites | 658 (43) | 967 (44) | ||
 Seattle | 224 (15) | 317 (14) | ||
 Denmark | 279 (18) | 457 (21) | ||
 Ontario | 159 (10) | 157 (7) | ||
Year of diagnosis | ||||
 1985–1988 | 238 (16) | 467 (21) | ||
 1989–1992 | 415 (27) | 647 (29) | ||
 1993–1996 | 427 (28) | 632 (29) | ||
 1997–2008 | 441 (29) | 466 (21) | ||
First degree family history of breast cancer | ||||
 No | 1004 (66) | 1706 (77) | ||
 Yes | 497 (33) | 466 (21) | ||
 Adopted/unknown | 20 (1) | 40 (2) | ||
Histology of first diagnosis | ||||
 Lobular | 179 (12) | 223 (10) | ||
 Other | 1338 (88) | 1986 (90) | ||
 Unknown | 4 (0) | 3 (0) | ||
Stage of first diagnosis | ||||
 Local | 1061 (70) | 1442 (65) | ||
 Regional | 448 (29) | 759 (34) | ||
 Unknown | 12 (1) | 11 (1) | ||
Estrogen receptor (ER) status of first diagnosisb | ||||
 Positive | 797 (52) | 1254 (57) | ||
 Negative | 467 (31) | 561 (25) | ||
 Other | 257 (17) | 397 (18) | ||
Progesterone receptor (PR) status of first diagnosisb | ||||
 Positive | 687 (45) | 1083 (49) | ||
 Negative | 442 (29) | 549 (25) | ||
 Other | 392 (26) | 580 (26) | ||
Chemotherapy | ||||
 No | 699 (46) | 923 (42) | ||
 Yes | 822 (54) | 1289 (58) | ||
Radiation treatment | ||||
 No | 641 (42) | 525 (24) | ||
 Yes | 880 (58) | 1686 (76) | ||
 Unknown | 0 (0) | 1 (0) | ||
Hormone treatment | ||||
 No | 964 (63) | 1270 (57) | ||
 Yes | 557 (37) | 940 (43) | ||
 Unknown | 0 (0) | 2 (0) | ||