Associations of obesity and physical activity with serum and intratumoral sex steroid hormone levels among postmenopausal women with breast cancer: analysis of paired serum and tumor tissue samples

Purpose: It has been hypothesized that intratumoral estrogens may play important roles in the growth of breast cancer. However, few studies have investigated such intratumoral hormones, or their association with risk factors of breast cancer. Methods: In this cross-sectional study, hormone levels in paired serum and tumor tissue samples from 146 postmenopausal women with breast cancer were measured by liquid chromatography-tandem mass spectrometry and compared between estrogen/progesterone (ER/PgR) subtypes. The associations of risk factors including body mass index (BMI) and other lifestyle factors with these hormone levels were investigated using analysis of covariance. Results: The level of estradiol (E2) in tumor tissue was extremely high in women with ER+ (geometric mean 95.6 pg/g) relative to women with ER−/PgR− (8.9 pg/g), whereas serum E2 level did not differ much between the two groups (3.1 and 2.8 pg/ml, respectively). Serum levels of precursors for E2, including testosterone (T) and androstenedione (Adione), and tissue Adione level, were high among women with ER+. After adjustment for confounding variables, BMI was found to be positively associated with tissue levels of E2, estrone (E1), T, and Adione among women with ER+ (P_trend < 0.0001 for E2; 0.0016 for E1; 0.0002 for T; and 0.03 for Adione). Conclusion: The data suggest that tissue E2 is related to the growth of receptor-positive breast cancer and that risk factors such as BMI affect tissue levels of E2 and its precursors. Understanding of hormonal environments within tumor tissue may be important for elucidating hormonal etiology of breast cancer and improving the prognosis of patients.