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Table 1 Baseline characteristics of the study group (72 breast cancer cases and 486 controls from the placebo arm of IBIS-I)

From: Mammographic breast density refines Tyrer-Cuzick estimates of breast cancer risk in high-risk women: findings from the placebo arm of the International Breast Cancer Intervention Study I

Variable

Controls

Cases

(n =486)

(n =72)

Follow-up (years) †

11.6 (10.7-12.3)

5.1 (3.1-7.9)

Age (years) †

49.5 (46.4-54.4)

49.9 (46.3-56.0)

BMI (kg/m 2 ) †

25.8 (23.4-29.1)

26.2 (23.7-28.4)

Menopausal status

  

Pre/peri

261 (54%)

38 (53%)

Post

225 (46%)

34 (47%)

HRT use

  

Never

316 (65%)

46 (64%)

Current

108 (22%)

14 (19%)

Previous

62 (13%)

12 (17%)

Age at menarche (years) †

13 (12-14)

13 (12-14)

Age at first birth

  

Nulliparous

69 (14%)

12 (17%)

>29 years

55 (11%)

6 (8%)

26-29 years

98 (20%)

14 (19%)

21-25 years

178 (37%)

27 (38%)

<21 years

86 (18%)

13 (18%)

Tyrer-Cuzick risk score

  

10-year absolute risk (%)†

5.5 (4.5-6.7)

5.4 (4.1-6.9)

10 -year relative risk†

2.2 (1.8-2.7)

2.1 (1.7-2.9)

Mammographic density

  

Percent dense area (%)†

42.5 (15.0-70.0)

62.5 (25.0-80.0)

  1. †Median (interquartile range). BMI, body mass index; HRT, hormone replacement therapy.
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Breast Cancer Research

ISSN: 1465-542X

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