An exploratory analysis of the association between levels of hormones implied in steroid biosynthesis and activity of abiraterone in patients with metastatic castration-resistant prostate cancer.

BACKGROUND: Abiraterone acetate, approved for patients with metastatic castration-resistant prostate cancer (mCRPC), blocks androgen byosinthesis. We aimed to describe changes determined by abiraterone in hormones implied in steroid biosynthesis, exploring association between hormonal levels and drug activity.

METHODS: Patients with mCRPC, receiving standard abiraterone + prednisone after docetaxel failure, were studied. We determined serum levels of progesterone, 17OH-progesterone, cortisol, ACTH, DHEA-sulphate, androstenedione, testosterone, sex hormone-binding globulin, aldosterone, plasma renin activity, and cholesterol, baseline and every 12 weeks. For each hormone, association with treatment activity was tested 1) comparing baseline values in responders vs. non-responders; 2) comparing progression-free survival (PFS) of patients with baseline low vs. high values; 3) comparing values after 12 weeks in responders vs. non-responders.

RESULTS: Forty-nine patients were analyzed; 26 patients (53.1%) experienced PSA response. Baseline values of all hormones were not statistically different between responders and non-responders. For all hormones, PFS difference of patients with low vs. high baseline values was not statistically significant. Several hormones showed significant and sustained changes vs. baseline, but all significant changes were similar between responders and non-responders.

CONCLUSIONS: This analysis does not suggest a significant association between baseline hormonal values, or changes induced by abiraterone, and treatment activity.