Abstract
Estradiol and estrone are well-established risk factors for postmenopausal breast cancer (BC). Experimental evidence suggests that specific estrogen metabolites, produced via irreversible hydroxylation of estrone and estradiol at the 2- or 16-position may independently influence carcinogenesis. We performed a nested case-control study of BC (328 BC cases; 639 controls) among postmenopausal women within the Nurses' Health Study (NHS)to examine the role of estrogens and estrogen metabolites (jointly referred to as EM). Plasma concentrations of each EM (unconjugated+conjugated forms) were measured by liquid chromatography-tandem mass spectrometry. Multivariable conditional logistic regression, adjusting for BC risk factors, estimated relative risks (RR) and 95% confidence intervals (CI) of BC across quintiles of individual EM, EM pathways, and pathway ratios. Associations by estrogen/progesterone receptor (ER/PR) status were analyzed by unconditional logistic regression. Estradiol and estrone were strongly associated with increased BC risk [estradiol: RRQ5v.Q1 (95% CI)=2.64 (1.64-4.26), estrone: 2.78 (1.74-4.45); both p-trends<0.001]. The 2-hydroxylation pathway was strongly associated with risk [RRQ5v.Q1=3.09 (1.81-5.27), p-trend<0.001], and remained so after adjusting for unconjugated estradiol [RRQ5v.Q1=2.23 (1.25-3.96), p-trend=0.01]. While the 16-hydroxylation pathway was modestly associated with risk [RRQ5v.Q1=1.62 (1.03-2.54), p-trend=0.01], the association was attenuated after unconjugated estradiol adjustment [RRQ5v.Q1=1.24 (0.77-1.99), p-trend=0.19]. Similar positive associations with the 2-pathway and 16-pathway were observed for ER+/PR+ and ER-/PR- tumors. In this cohort of postmenopausal women, 2-hydroxylation of estrone and estradiol was associated with increased BC risk, independent of unconjugated estradiol. These results highlight the need to revisit the role of estrogen metabolism in BC etiology and prevention.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
