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
| 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 |
Abbreviations: OR (95% CI) odds ratio (95% confidence interval)
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
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”
dAdjusted as in a plus number of exposures (≤5;>5)
eAfter = also includes chest X-ray exposure that occurred during the same year of first full-term pregnancy
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)