Association of HSD3B1 Genotype and Clinical Outcomes in Postmenopausal Estrogen-Receptor-Positive Breast Cancer

Background Homozygous inheritance of a single-nucleotide polymorphism (1245A > C) in HSD3B1 results in an adrenal permissive phenotype of increased adrenal steroid precursor conversion to potent androgens. This is associated with poor outcomes in prostate cancer. We hypothesized that inheritance of the HSD3B1 adrenal permissive genotype would similarly negatively impact breast cancer outcomes. Patients and Methods Germline HSD3B1 was sequenced in 644 postmenopausal women diagnosed between 2004 and 2015 with stage I–III estrogen receptor-positive (ER + ), HER2/neu-negative (HER2 − ) breast cancer enrolled in a population-based study in western Washington. Primary endpoint was distant metastatic recurrence according to genotype. Secondary endpoint was breast cancer-specific survival. Hazard ratios (HR) were calculated using cause-specific Cox regression accounting for competing risks. Results Adrenal restrictive genotype (homozygous wild type) was most prevalent (47%), followed by heterozygous (44%) and adrenal permissive (9%). There were no significant differences comparing demographic, tumor, or treatment characteristics apart from higher frequency of adrenal permissive genotype among non-Hispanic white participants ( p = 0.04). After accounting for competing risks, the cumulative incidence of distant metastatic recurrence (15 events) was significantly higher among participants with adrenal permissive compared with the adrenal restrictive genotype (HR 4.9, 95% CI 1.32–18.4, p = 0.02). The adrenal permissive genotype was also predictive of breast cancer-specific mortality (HR 3.5, 95% CI 1.27–9.59, p = 0.02). Conclusions Inheritance of the HSD3B1 adrenal permissive genotype is associated with increased incidence of distant metastasis and higher cause-specific mortality in postmenopausal ER + /HER2 − breast cancer. Further research is necessary to understand the effect of excess adrenal androgen metabolism in promoting breast cancer growth and progression.