LAUSR

Micro‐Abstract The HSD3B1 (1245C) variant is predictive of response to ADT in castration sensitive prostate cancer (CSPC) and to ketoconazole in castration resistant prostate cancer (CRPC). We hypothesized that the HSD3B1 (1245C) variant would be predictive of response to abiraterone acetate (AA). In 76 men with metastatic CRPC, the HSD3B1 (1245C) variant was not predictive of response to first‐line AA. Background: The HSD3B1 gene encodes the enzyme 3&bgr;‐hydroxysteroid dehydrogenase‐1 (3&bgr;HSD1), which catalyzes adrenal androgen precursors into dihydrotestosterone, the most potent androgen. Recently, the HSD3B1 (1245C) variant was shown to predict shorter duration of response to androgen deprivation therapy with medical or surgical castration in the setting of castration‐sensitive prostate cancer (CSPC). The HSD3B1 (1245C) variant also predicts longer duration of response to ketoconazole in men with castration‐resistant prostate cancer (CRPC). We hypothesized that the HSD3B1 (1245C) variant predicts response to treatment with abiraterone acetate (AA) and can help personalize treatment in men with advanced prostate cancer. Methods: Clinical data and samples were from a prospectively maintained prostate cancer registry at the University of Utah. Genotyping was performed. The primary study end point was progression‐free survival in first‐line AA in men with metastatic CRPC. We performed prespecified multivariate analyses to assess the independent predictive value of HSD3B1 genotype on progression‐free survival on AA. Results: Seventy‐six men with metastatic CRPC treated with first‐line AA were included. In multivariate analysis, the HSD3B1 (1245C) variant did not predict response to first‐line AA. Conclusion: The HSD3B1 (1245C) variant does not predict response to first‐line AA in metastatic CRPC. This finding could be due to the ability of AA metabolites to act as both agonist (3‐keto‐5&agr;‐abiraterone) and antagonist (&Dgr;4‐abiraterone) on androgen signaling.