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Table 1 Characteristics of breast cancer case participants and control participants

From: Reproductive factors and the risk of triple-negative breast cancer in white women and African-American women: a pooled analysis

  Overall By study
Women’s CARE Women’s BCIS Women’s LIFE
Case participants N = 2658 N = 1197 N = 342 N = 1119
Mean age at diagnosis, years (SD, range) 46.7 (8.1, 22-64) 49.0 (8.6, 35-64) 51.8 (7.3, 35-64) 42.7 (5.4, 22-49)
Race
 White 1960 (73.7%) 678 (56.6%) 287 (83.9%) 995 (88.9%)
 African-American 698 (26.3%) 519 (43.4%) 55 (16.1%) 124 (11.1%)
Subtype of breast cancer
 Triple-negative 554 (20.8%) 335 (28.0%) 21 (6.1%) 198 (17.7%)
 Luminal A-like 1517 (57.1%) 645 (53.9%) 233 (68.1%) 639 (57.1%)
 Luminal B-like 360 (13.5%) 121 (10.1%) 49 (14.3%) 190 (17.0%)
 HER2-enriched 227 (8.5%) 96 (8.0%) 39 (11.4%) 92 (8.2%)
Control participants N = 2448 N = 2011a N = 437
Mean age at reference date, years (SD, range) 47.8 (8.3, 24-64) 48.9 (8.4, 35-64) 42.6 (4.9, 24-49)
Race
 White 1549 (63.3%) 1147 (57.0%) 402 (92.0%)
 African-American 899 (36.7%) 864 (43.0%) 35 (8.0%)
Mean age at menarche, years (SD) 12.4 (1.6) 12.4 (1.6) 12.7 (1.5)
Ever had a completed (>26-week) pregnancy 1990 (81.3%) 1677 (83.4%) 313 (71.6%)
Among parous women N = 1990 N = 1677   N = 313
 Mean number of completed pregnancies (SD) 2.7 (1.5) 2.8 (1.6) 2.2 (1.1)
 Mean age at first completed pregnancy (SD) 23.2 (5.7) 22.5 (5.3) 27.1 (6.2)
 Ever breastfed 1242 (62.4%) 967 (57.7%) 275 (87.9%)
 Mean duration of breastfeeding among those who breastfed, months (SD) 12.1 (15.0) 10.9 (14.4) 16.2 (16.5)
  1. aIncluding those who also served as controls in the Women’s BCIS. Triple-negative = estrogen receptor (ER)–/progesterone receptor (PR)–/human epidermal growth factor receptor-2 (HER2)–, Luminal A-like = ER+ and/or PR+ plus HER2–, Luminal B-like = ER+ and/or PR+ plus HER2+, HER2-enriched = ER–/ PR–/HER2+. CARE Contraceptive and Reproductive Experiences Study, BCIS Breast Carcinoma in situ Study, LIFE Learning the Influence of Family and Environment Study