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Table 6 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 gene group

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
Gene group
Group “Low”f Group “No Effect”f Group “High”f
Chest X-ray exposure
 No 34 67 1   61 81 1   65 91 1   
 Yes 234 371 2.02 1.16–3.52 354 416 1.62 1.03–2.55 495 400 3.31 2.14–5.12 0.0038
Number of exposures
 0 34 67 1   61 81 1   65 91 1   
 <10 119 183 2.01 1.12–3.59 184 215 1.53 0.95–2.46 256 219 2.98 1.89–4.70  
 ≥10 47 75 2.19 1.09–4.40 67 85 2.04 1.14–3.66 94 78 3.88 2.23–6.75 0.022
 Continuous    1.02 0.99–1.04    1.02 1.00–1.04    1.04 1.02–1.06 0.032
Age at first exposure, yearsd
 No exposure 34 67 0.55 0.30–1.01 61 81 0.83 0.51–1.37 65 91 0.38 0.23–0.61 0.43
 ≥20 90 163 1   124 188 1   179 180 1   
 <20 101 143 1.24 0.80–1.91 166 165 1.38 0.94–2.03 222 159 1.27 0.90–1.80  
 Continuous    1.00 0.9–1.02    0.99 0.98–1.01    1.00 0.98–1.01 0.78
According to first full-term pregnancy (FFTP)d
 Only after FFTPe 52 75 1   68 91 1   95 92 1   
 Before (incl. no FTP) 142 242 0.82 0.49–1.38 231 271 0.90 0.57–1.40 311 257 1.04 0.69–1.57 0.48
  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), plus two other DNA repair rare variants groups (when analysis by group of DNA repair rare variants), with missing included in reference categories for each variable
  3. bBecause of the non-exclusivity of the 3 groups, P value for heterogeneity test was performed on the ranked Group variable : at least 1 variant in Group “High,” no variant in Group “High,” and at least 1 variant in Group “No Effect,” only at least 1 variant in Group “Low”
  4. dAdjusted as in a plus number of exposures (≤5;>5)
  5. eAfter = also includes chest X-ray exposure that occurred during the same year of first full-term pregnancy
  6. fIndividuals carrying at least one variant in one of the Gene Groups: Group “Low” (OR<0.9) ; Group “No Effect” (0.9<=OR<=1.1); Group “High” (OR>1.1)