Table 4 Breast cancer risk associated with hormonal potency and content of combination oral contraceptives used for the longest duration within 5 years of interview

From: Hormonal content and potency of oral contraceptives and breast cancer risk among young women

 

<35 years

35–44 years

Total (<45 years)

 

Cases ( N =193)

Controls ( N =219)

RR

95% CI

Cases ( N =487)

Controls ( N =445)

RR

95% CI

Cases ( N =680)

Controls ( N =664)

RR

95% CI

Nonusers

58

96

1.00

 

313

310

1.00

 

371

406

1.00

 

Oestrogen dose

            

 Ethinyl estradiol

            

⩽35 μg

81

80

1.91

1.1–3.2

80

67

1.02

0.7–1.5

161

147

1.27

0.9–1.7

>35 μg

27

17

3.62

1.7–7.9

32

21

1.52

0.8–2.8

59

38

1.99

1.2–3.2

 Mestranol

            

⩽50 μg

14

17

1.17

0.5–2.8

29

21

1.52

0.8–2.9

43

38

1.38

0.8–2.3

>50 μg

5

4

2.40

0.5–11.8

12

10

1.25

0.5–3.1

17

14

1.52

0.7–3.3

 Unknown

8

5

1.93

0.5–6.8

21

16

1.31

0.6–2.7

29

21

1.52

0.8–2.8

Progestin content

            

 Ethynodiol diacetate

12

3

12.0

2.4–59.2

8

10

0.82

0.3–2.2

20

13

1.94

0.9–4.2

 Norethindrone

67

73

1.64

1.0–2.8

86

65

1.32

0.9–2.0

153

138

1.35

1.0–1.8

 Norethindrone acetate

8

5

3.11

0.9–10.6

17

10

1.77

0.7–4.3

25

15

1.90

0.9–3.8

 Norgestrel

21

17

1.97

0.9–4.5

25

23

0.71

0.4–1.3

46

40

1.14

0.7–1.9

 Levonorgestrel

20

21

2.12

1.0–4.7

20

12

1.77

0.8–4.0

40

33

1.66

1.0–2.9

 Unknown

7

4

2.36

0.6–9.4

18

15

1.30

0.6–2.8

25

19

1.59

0.8–3.1

Progestin potency

            

 Low

114

115

1.83

1.1–3.0

140

103

1.28

0.9–1.8

254

218

1.40

1.1–1.8

 High

14

4

8.11

2.1–31.6

16

17

0.84

0.4–1.8

30

21

1.54

0.8–2.8

 Unknown

7

4

2.35

0.6–9.3

18

15

1.30

0.6–2.8

25

19

1.59

0.8–3.0

Oestrogen potency

            

 Low

120

113

1.97

1.2–3.2

138

107

1.18

0.8–1.7

258

220

1.38

1.1–1.8

 High

8

6

2.56

0.7–8.9

18

13

1.50

0.7–3.2

26

19

1.70

0.9–3.3

 Unknown

7

4

2.32

0.6–9.2

18

15

1.30

0.6–2.8

25

19

1.58

0.8–3.0

Progestin/oestrogen potency

            

 Low/low

106

109

1.79

1.1–2.9

126

93

1.27

0.9–1.8

232

202

1.37

1.0–1.8

 Low/high

8

6

2.53

0.7–8.8

14

10

1.50

0.6–3.6

22

16

1.71

0.8–3.4

 High/low

14

4

8.07

2.1–31.4

12

14

0.71

0.3–1.6

26

18

1.52

0.8–2.9

 High/high

0

0

4

3

1.54

0.3–7.3

4

3

1.67

0.4–7.9

  

 Unknown

7

4

2.34

0.6–9.3

18

15

1.31

0.6–2.8

25

19

1.58

0.8–3.0

  1. Note: This table compares nonusers to women who used oral contraceptives within 5 years of interview. Subjects who used oral contraceptives, but not within 5 years of interview, were excluded from analysis (N=1788). RRs and 95% CIs were estimated using maximum likelihood methods and adjusting for age, site, race, menopausal status, a combination variable for age at first birth and number of births, age at menarche, family history of breast cancer, body mass index, and mammography use.
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