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Table 2 Association between tumor characteristics of first primary breast cancer and contralateral breast cancer risk

From: Hormone receptor status of a first primary breast cancer predicts contralateral breast cancer risk in the WECARE study population

First primary breast cancer Cases, N (%) Controls, N (%) RRa (95% CI)
Histology
 Non-lobular 1338 (88) 1986 (90) 1.0 (ref.)
 Lobular 179 (12) 223 (10) 1.3 (1.0, 1.6)
 Unknown 4 (0) 3 (0)  
Grade
 Well 248 (16) 338 (15) 1.0 (ref.)
 Moderate 417 (27) 688 (31) 0.8 (0.7, 1.1)
 Poor/undifferentiated 503 (33) 640 (29) 1.1 (0.8, 1.4)
 Unknown 353 (23) 546 (25)  
Stage
 Localized 1061 (70) 1442 (65) 1.0 (ref.)
 Regional 448 (29) 759 (34) 1.0 (0.9, 1.2)
 Unknown 12 (1) 11 (1)  
Lymph node status
 Negative 1045 (69) 1426 (64) 1.0 (ref.)
 Positive 438 (29) 751 (34) 1.0 (0.8, 1.2)
 No nodes sampled 22 (2) 26 (1) 1.3 (0.7, 2.4)
 Unknown 16 (1) 9 (0)  
Tumor size
 ≤10 mm 335 (22) 510 (23) 1.0 (ref.)
 >10 to ≤20 mm 595 (39) 913 (41) 1.1 (0.9, 1.3)
 >20 mm 477 (31) 662 (30) 1.1 (0.9, 1.4)
 Inflammatory 6 (0) 2 (0)  
 Unknown 108 (7) 125 (6)  
ER status
 Positive 797 (52) 1254 (57) 1.0 (ref.)
 Negative 467 (31) 561 (25) 1.3 (1.1, 1.6)
 Other/unknownb 257 (17) 397 (18)  
PR status
 Positive 687 (45) 1083 (49) 1.0 (ref.)
 Negative 442 (29) 549 (25) 1.2 (1.0, 1.5)
 Other/unknownb 392 (26) 580 (26)  
Joint ER/PR status
 ER+/PR+ 621 (41) 958 (43) 1.0 (ref.)
 ER+/PR- 85 (6) 142 (6) 1.0 (0.7, 1.4)
 ER-/PR- 352 (23) 387 (18) 1.4 (1.1, 1.7)
 Other/unknownb,c 463 (30) 725 (33)  
HER2 statusd
 Negative 207 (25) 222 (27) 1.0 (ref.)
 Positive 53 (7) 63 (8) 0.8 (0.5, 1.3)
 Unknownb 553 (68) 528 (65)  
Triple-negatived
 No 514 (63) 579 (71) 1.0 (ref.)
 Yes 59 (7) 40 (5) 1.3 (0.8, 2.2)
 Other/unknownb 240 (30) 194 (24)  
  1. Abbreviations: RR risk ratio, CI confidence interval, N number, ER estrogen receptor, PR progesterone receptor, HER2 human epidermal growth factor receptor 2. aAdjusted for age at first breast cancer diagnosis, first-degree family history of breast cancer, histologic assessment, menopausal status, age at menarche, parity, radiation, chemotherapy and hormone therapy at first breast cancer diagnosis. Model examining histology was not adjusted for histologic assessment. b“Other/unknown” category consists of women for whom no laboratory test was given, the test was given and the results were unknown or the test was given and the results were borderline; estimates not reported. The start date for ER/PR reporting in SEER was 1 January 1990 [47]. cIncludes 59 cases and 108 controls classified as ER-/PR+. dAmong participants in the Women’s Environmental Cancer and Radiation Epidemiology II Study (WECARE II) only; HER2 status not queried for WECARE I participants. Surveillance, Epidemiology, and End Results (SEER) Registry only began collecting HER2 status in 2010 [46]