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Table 1 Age-standardized characteristics of the controls at breast biopsy by EZH2 expression category

From: EZH2 protein expression in normal breast epithelium and risk of breast cancer: results from the Nurses’ Health Studies

 

Category of EZH2 expression in normal TDLU epithelium

0–10% (n = 184)

11–20% (n = 55)

>20% (n = 30)

Age at cancer diagnosis/index datea

52.92 (8.20)

50.35 (7.20)

47.77 (8.11)

Year of BBD biopsy

 Before 1980, %

42

33

46

 1980–1989, %

44

53

43

 After 1989, %

14

14

11

Time from biopsy to diagnosis/index date

 0.5–4.9 years, %

48

50

45

 5.0–9.9 years, %

25

23

18

 10.0–14.9 years, %

19

20

34

 15.0+ years, %

9

7

4

BBD category

 Non-proliferative, %

32

28

29

 Proliferative without atypia, %

53

61

66

 Atypical hyperplasia, %

15

12

5

Age at first birth

 Nulliparous, %

6

2

0

 <25 years, %

57

42

71

 25–29 years, %

30

42

13

 30+ years, %

6

11

5

 Missing, %

2

3

11

Duration of breastfeeding (months)b

 0 months, %

37

37

22

 0–3 months, %

20

19

50

 4–11 months, %

20

26

7

 12+ months, %

21

15

18

 Missing, %

2

4

2

Age at menarche (years)

  < 12, %

24

19

20

 12, %

26

19

32

 13, %

26

41

32

 14+, %

23

21

16

Menopausal status/age at menopause (years)

 Premenopausal, %

42

43

48

  < 50, %

29

30

36

 50+, %

24

19

16

 Missing, %

5

9

0

Postmenopausal hormone therapy use

 Never, %

26

24

33

 Ever, %

30

25

16

 Premenopausal, %

43

49

51

 Missing, %

1

2

0

Oral contraceptive use

 Never, %

51

50

34

 Ever, %

46

50

66

 Missing, %

3

0

0

BMI (kg/m2)

  < 25.0, %

61

68

71

 25.0–29.9, %

26

14

26

 30.0+, %

13

17

4

Weight change since age 18 years

 Gain <2 kg, %

17

13

16

 Gain 2–10 kg, %

34

39

46

 Gain 10+ kg, %

39

44

32

 Missing, %

10

3

5

Alcohol consumption (g/week)

 None, %

37

36

36

 0.1–4.9, %

32

32

42

 5.0–14.9, %

23

15

11

 15.0+, %

9

17

11

Family history of breast cancer

 No family history, %

81

91

82

 Family history, %

19

9

18

  1. Values are means (SD) or percentages and are standardized to the age distribution of the study population. Values of polytomous variables may not sum to 100% due to rounding. aValue is not age-adjusted. bFor parous women only. EZH2 enhancer of zeste homolog 2, TDLU normal terminal ductal lobular units, BMI body mass index, BBD benign breast disease