Evaluating the hypothalamic-pituitary-adrenal axis (HPAA) in men receiving ketoconazole for castrate-resistant prostate cancer (CRPC).

Abstract

64 Background: Serum adrenal androgen (AA) levels may be prognostic for survival in men with CRPC treated with androgen synthesis inhibitors (ASIs) including ketoconazole (keto) and abiraterone. We hypothesize that up-regulation of the HPAA and adrenocorticotropic hormone (ACTH) may contribute to therapeutic resistance on ASIs. The current study explores the relationship between ACTH, AA, testosterone (T) and estradiol (E) among CRPC patients (pts) treated with ASI + corticosteroids. Methods: Phase 2 study of keto (400 mg TID) + hydrocortisone (HC) (30 mg/day) in pts with CRPC. Pts who achieved ≥ 30% PSA decline from baseline at week 12 continued keto/HC until progression, at which point HC was replaced by dexamethasone (dex). Serum hormone (H) levels were measured (in AM) at baseline and every 4 weeks using standard assays. Statistical tests include Spearman’s rank test for correlation between baseline H levels; Wilcoxon matched pairs for baseline vs. week 4 distribution; and Fisher’s exact test for associations between H levels (dichotomized at median) with PSA decline. Results: Of 30 pts enrolled and 24 evaluable for PSA response, 13 pts (54%) achieved ≥ 30% PSA decline at 12 weeks. Baseline ACTH was positively correlated with DHEA (r = 0.40; p = 0.04) and cortisol (r = 0.52; p = 0.007). Change from baseline to week 4 in H levels is shown in table. There was a significant increase in pts achieving a PSA decline of ≥ 30% if there was a decrease in E at week 4 vs. no decrease (83% vs. 18%; p = 0.003). Baseline and changes in other H levels were not associated with PSA outcome at week 12. Conclusions: ACTH is positively correlated with DHEA and cortisol in CRPC pts. Declines in E may serve as an additional predictive marker of benefit for ASI therapy. These observations require prospective validation. Analyses exploring changes in ACTH at disease progression and impact of substituting dex for HC are ongoing. Clinical trial information: NCT01036594. [Table: see text]