Early radiation exposures and BRCA1-associated breast cancer in young women from Poland.

To study whether or not there is an adverse effect of early chest X-rays on breast cancer risk in breast cancer susceptibility gene 1 (BRCA1) carriers, we compared the histories of chest X-ray exposures before age 30 in 138 BRCA1 carriers with breast cancer with 158 age-matched women with breast cancer, but without a BRCA1 mutation. All cases were drawn from a national breast cancer research registry. Affected carriers reported more frequent chest X-ray use before age 20 than affected non-carriers (0.6 vs. 0.3; P = 0.01). Affected carriers had, on average, 1.8 chest X-rays before age 30 compared to an average of 1.0 for affected non-carriers (P = 0.002). The odds ratio for ever having had a chest X-ray below age 30, given a BRCA1 mutation, was 1.8 [95% confidence interval (CI) = 1.2-2.9; P = 0.01]. These observations support the hypothesis that early radiation exposure may be a risk factor for breast cancer in BRCA1 carriers.