Efficacy of eplerenone in the management of mineralocorticoid excess in men with metastatic castration resistant prostate cancer treated with abiraterone without prednisone

Abstract Background Abiraterone acetate (hereafter abiraterone) is approved for metastatic castration refractory prostate cancer (mCRPC). Co-administration with prednisone is recommended to prevent toxicity from secondary mineralocorticoid excess such as hypertension, hypokalemia and edema. However, use of prednisone is often not desirable by patients because of potential for detrimental effects of long term therapy with corticosteroids, especially in those with comorbidities like diabetes or who have received prior immunotherapeutics. Eplerenone is a non-steroidal mineralocorticoid antagonist demonstrated to abrogate mineralocorticoid excess. In this retrospective study, we report real world experience of use of eplerenone with abiraterone in men with mCRPC who wished to avoid concomitant prednisone therapy. Methods Incidence and grade (CTCAE v4) of mineralocorticoid excess toxicities, along with baseline demographics, disease characteristics, and PFS in men with mCRPC treated with abiraterone, not willing to be treated with corticosteroids and thus received eplerenone were collected retrospectively, and compared with those treated with abiraterone and prednisone during the same time period. Continuous variables were assessed by Wilcoxon rank sum or student t-test, and categorical variables were assessed by Fischer's Exact test or chi-square as appropriate. PFS was compared by Kaplan-Meier method. Results Of 106 men treated with abiraterone, 40 received eplerenone and 66 received prednisone. Baseline and disease characteristics, incidence and grades of adverse events related to syndrome of mineralocorticoid excess, and median PFS were similar in both cohorts. Conclusions In real world population of men with mCRPC treated with abiraterone, corticosteroids may be avoided by concomitant treatment with eplerenone. Data need further validation.