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Table 5 Effect of lifetime chest X-ray exposure (any exposure) on breast cancer risk according to the number of exposures, the age at first exposure, and the first full-term pregnancy by birth cohort

From: Diagnostic chest X-rays and breast cancer risk among women with a hereditary predisposition to breast cancer unexplained by a BRCA1 or BRCA2 mutation

 

Number of

Number of

Number of

Pb

Cases

Ctrls

ORa

95% CI

Cases

Ctrls

ORa

95% CI

Cases

Ctrls

ORa

95% CI

Birth cohort

≤ 1945

1946–1959

≥ 1960

Chest X-ray exposure

 No

47

31

1

 

96

92

1

 

65

116

1

  

 Yes

431

259

1.57

0.72-3.43

678

605

1.65

1.06–2.56

195

240

2.54

1.63–3.98

0.024

Number of exposures

 0

47

31

1

 

96

92

1

 

65

116

1

  

 1–3

134

81

1.72

0.74–3.98

179

197

1.24

0.75–2.05

79

112

2.04

1.22–3.40

 

 4–9

81

46

2.04

0.82–5.07

122

111

1.70

0.98–2.94

48

43

3.77

2.03–7.01

0.041

 ≥10

105

64

1.44

0.60–3.45

142

130

2.26

1.31–3.90

16

21

2.77

1.19–6.47

 

 Continuous

  

1.01

0.99–1.03

  

1.04

1.02–1.06

  

1.06

1.01–1.12

0.013

Age at first exposure, yearsc

 No exposure

47

31

0.52

0.23–1.21

96

92

0.77

0.47–1.25

65

116

0.47

0.28–0.78

 

 ≥20

163

119

1

 

237

261

1

 

85

110

1

  

 15–19

87

45

0.74

0.38–1.42

159

123

1.07

0.69–1.66

42

54

1.13

0.64–2.00

0.67

 <15

122

64

0.83

0.47–1.46

140

114

1.40

0.89–2.18

28

41

0.91

0.47–1.79

 

 Continuous

  

1.01

0.99–1.02

  

1.00

0.98–1.01

  

1.02

0.99–1.05

0.49

According to first full-term pregnancy (FFTP)c

 Only after FFTPd

109

59

1

 

124

139

1

 

35

34

1

  

 Before (incl. no FTP)

268

175

0.48

0.27–0.86

429

373

0.95

0.63–1.44

128

177

0.86

0.45–1.63

0.19

  1. Abbreviations: OR (95% CI) odds ratio (95% confidence interval
  2. aAdjusted for age at censoring (when by birth cohort analysis) and for birth cohort (continuous) (when by age at censure analysis), number of full-term pregnancies (>2; 1–2; 0), mammography use (never; ever), educational level (intermediate/high; basic; not graduated), BMI (18.5–24.99; <18.5; ≥25 and <30; ≥30), smoking (no; current; past), and family history of breast cancer (0;1st degree; 2nd degree)
  3. bP value for heterogeneity test
  4. cAdjusted as in a plus number of exposures (≤5; >5)
  5. dAfter = also includes chest X-ray exposure that occurred during year of first full-term pregnancy