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Table 8 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 estrogen receptor tumor status

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

  Estrogen receptor (ER) tumor status
ER negative ER positive   Unknown
Controls Cases ORa 95% CI Cases ORa 95% CI Pb Cases ORa 95% CI
Chest X-ray exposure
 No 239 32 1   107 1    69 1  
 Yes 1104 132 1.50 0.94–2.39 692 2.13 1.56–2.91 0.16 480 2.21 1.51–3.24
Number of exposures
 0 239 32 1   107 1    69 1  
 1–3 390 43 1.31 0.77–2.25 207 1.73 1.22–2.46 0.67 142 1.87 1.21–2.87
 4–9 200 29 1.99 1.10–3.62 140 2.65 1.80–3.92   82 2.51 1.55–4.07
 ≥10 215 21 1.51 0.79–2.90 124 2.23 1.49–3.33   118 3.27 2.03–5.28
 Continuous    1.01 0.99–1.04   1.02 1.00–1.03 0.58   1.03 1.01–1.05
Age at first exposure, yearsc
 No exposure 239 32 0.70 0.41–1.19 107 0.53 0.38–0.75   69 0.53 0.35–0.81
 ≥20 490 52 1   263 1    170 1  
 15–19 222 33 1.06 0.64–1.78 154 1.07 0.78–1.47 0.66 101 0.86 0.58–1.27
 <15 219 27 1.13 0.66–1.94 139 1.04 0.75–1.44   124 1.25 0.86–1.82
 Continuous    1.01 0.99–1.03   1.01 0.99–1.02 0.39   1.00 0.99–1.01
According to first full-term pregnancy (FFTP)c
 Only after FFTPd 232 35 1   141 1    92 1  
 Before (incl. no FTP) 725 79 0.66 0.41–1.07 435 0.83 0.61–1.13 0.22 311 0.84 0.58–1.22
  1. Abbreviations: OR (95% CI) odds ratio (95% confidence interval)
  2. aAdjusted for age at censoring, birth cohort (≤1945; 1946–1959; ≥1960), 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 breast cancer family history (0;1st degree; 2nd degree)
  3. bP value for χ2 heterogeneity test between ER-negative and ER-positive tumors
  4. cAdjusted as in a plus number of exposures (≤5;>5)
  5. dAfter = also includes chest X-ray exposure that occurred during the same year of first full-term pregnancy