Circulating estrogens and estrogens within the breast among postmenopausal BRCA1/2 mutation carriers

Accurately quantifying parent estrogens (PE) estrone (E₁) and estradiol (E₂) and their metabolites (EM) within breast tissue and serum may permit detailed investigations of their contributions to breast carcinogenesis among BRCA1/2 mutation carriers. We conducted a study of PE/EM in serum, nipple aspirate fluid (NAF), and ductal lavage supernatant (DLS) among postmenopausal BRCA1/2 mutation carriers. PE/EM (conjugated and unconjugated) were measured in paired serum/NAF (n = 22 women) and paired serum/DLS samples (n = 24 women) using quantitative liquid chromatography–tandem mass spectrometry (LC/MS/MS). The relationships between serum and tissue-specific PE/EM were measured using Pearson’s correlation coefficients. Conjugated forms of PE/EM constituted the majority of estrogen in serum (88 %), NAF (59 %) and DLS (69 %). PE/EM in NAF and serum were highly correlated [E₁ (r = 0.97, p < 0.0001), E₂ (r = 0.90, p < 0.0001) and estriol (E₃) (r = 0.74, p < 0.0001)] as they were in DLS and serum [E₁ (r = 0.92, p < 0.0001; E₂ (r = 0.70, p = 0.0001; E₃ (r = 0.67, p = 0.0004)]. Analyses of paired total estrogen values for NAF and serum, and DLS and serum yielded ratios of 0.22 (95 % CI 0.19–0.25) and 0.28 (95 % CI 0.24–0.32), respectively. This report is the first to employ LC/MS/MS to quantify PE/EM in novel breast tissue-derived biospecimens (i.e., NAF and DLS). We demonstrate that circulating PE and EM are strongly and positively correlated with tissue-specific PE and EM measured in NAF and DLS among postmenopausal BRCA1/2 mutation carriers. If confirmed, future etiologic studies could utilize the more readily obtainable serum hormone levels as a reliable surrogate measure of exposure at the tissue level.