Associations of ionizing radiation and breast cancer-related serum hormone and growth factor levels in cancer-free female a-bomb survivors

Abstract

Levels of exposure to ionizing radiation are increasing forwomen worldwide due to the widespread use of CT and otherradiologic diagnostic modalities. Exposure to ionizing radiationas well as increased levels of estradiol and other sex hormonesare acknowledged breast cancer risk factors, but the effects ofwhole-body radiation on serum hormone levels in cancer-freewomen are unknown. This study examined whether ionizingradiation exposure is associated with levels of serum hormonesand other markers that may mediate radiation-associated breastcancer risk. Serum samples were measured from cancer-freewomen who attended biennial health examinations with a widerange of past radiation exposure levels (N = 412, ages 26-79).The women were selected as controls for separate case-controlstudies from a cohort of A-bomb survivors. Outcome measuresincluded serum levels of total estradiol, bioavailable estradiol,testosterone, progesterone, prolactin, insulin-like growth factor-1 (IGF1), insulin-like growth factor-binding protein 3 (IGFBP-3), and ferritin. Relationships were assessed using repeatedmeasuresregression models fitted with generalized estimatingequations. Geometric mean serum levels of total estradiol andbioavailable estradiol increased with 1 Gy of radiation doseamong samples collected from postmenopausal women (17%1Gy,95% CI: 1%-36% and 21%1Gy, 95% CI: 4%-40%, respectively),while they decreased in samples collected from premenopausalwomen (211%1Gy, 95% CI: 220%-1% and 212%1Gy, 95% CI:220%- 22%, respectively). Interactions by menopausal statuswere significant (P = 0.003 and P 0.001, respectively).Testosterone levels increased with radiation dose in postmenopausalsamples (30.0%1Gy, 95% CI: 13%-49%) while theymarginally decreased in premenopausal samples (210%1Gy, 95%CI: 219%-0%) and the interaction by menopausal status wassignificant (P 0.001). Serum levels of IGF1 increased linearlywith radiation dose (11%1Gy, 95% CI: 2%-18%) and there was asignificant interaction by menopausal status (P = 0.014).Radiation-associated changes in serum levels of estradiol,bioavailable estradiol, testosterone and IGF1 were modified bymenopausal status at the time of collection. No associations withradiation were observed in serum levels of progesterone,prolactin, IGFBP-3 or ferritin. © 2011 by Radiation Research Society.