Trabert B, et al. - In a nested case-control study in the Women's Health Initiative (WHI) Observational Study (OS), the links between pre-diagnostic serum levels of 12 androgens (including novel androgen metabolites that reflect androgen activity in tissues) and ovarian cancer risk were assessed using highly sensitive LC-MS/MS assays among postmenopausal women. A total of 169 ovarian cancer cases were included, frequency-matched to 410 controls from the WHI-OS who were not using menopausal hormones at enrollment/blood draw. Multivariable adjusted logistic regression was used to assess the links overall and by subtype (n=102 serous/67 non-serous). An increased risk of developing non-serous ovarian cancer was observed in association with androsterone-glucuronide and total glucuronide metabolites. Findings highlight the importance of sex steroid metabolism in the etiology of non-serous ovarian cancers. Across histologic subtypes of ovarian cancer, a heterogeneous hormonal etiology was supported.