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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