1191Endogenous hormones and risk of invasive breast cancer in pre- and post-menopausal women. (2nd September 2021) - Tin, Sandar Tin
Abstract: Background: Some endogenous hormones have been associated with breast cancer risk, but the nature of these relationships is not fully understood. We investigated the associations between serum concentrations of testosterone, sex hormone binding globulin (SHBG), insulin-like growth factor-1 (IGF-1) and oestradiol (pre-menopausal women only) and the risk of invasive breast cancer using data from UK Biobank. Methods: We included 30, 565 pre-menopausal and 133, 294 post-menopausal women in this analysis. Hormone concentrations were measured in serum collected between 2006 and 2010, and incident cancer cases were identified through linkage to cancer and death registries. Multivariable Cox proportional hazards models were used, and hazard ratios (HRs) were corrected for regression dilution bias using repeat measures collected in about 5, 000 women four years after recruitment (except for oestradiol). Results: During a median follow-up of 7.1 years, 527 pre-menopausal and 2, 997 post-menopausal women were diagnosed with invasive breast cancer. Cancer risk was positively associated with testosterone in post-menopausal women (HR per 0.5 nmol/L increment: 1.18; 95% CI: 1.14, 1.23) but not in premenopausal women (pheterogeneity=0.03), and with IGF-1 (HR per 5 nmol/L increment: 1.18; 1.02, 1.35 (pre-menopausal) and 1.07; 1.01, 1.12 (post-menopausal); pheterogeneity=0.2), and inversely associated with SHBG (HR per 30 nmol/L increment: 0.96; 0.79, 1.15 (pre-menopausal) and 0.89; 0.84, 0.94 (post-menopausal); pheterogeneity=0.4). Oestradiol was not associated with risk, but there were study limitations for this hormone. Conclusions: This study confirms associations of testosterone, IGF-1 and SHBG with breast cancer risk, with heterogeneity by menopausal status for testosterone. Key messages: Breast cancer risk was positively associated with testosterone and inversely associated with SHBG in post-menopausal women, and positively associated with IGF-1 in both pre- and post-menopausal women.