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Abstract: TH-PO154

Abiraterone Acetate: Enough of the S.A.M.E. Old Steroids

Session Information

Category: Trainee Case Report

  • 1500 Onco-Nephrology

Authors

  • Shah, Anita, Baylor College of Medicine, Houston, Texas, United States
  • Shah, Maulin, Baylor College of Medicine, Houston, Texas, United States
Introduction

Abiraterone acetate is an androgen synthesis inhibitor, which suppresses testosterone production, utilized in the treatment of castrate-resistant prostate cancer. We report a case of syndrome of apparent mineralocorticoid excess (SAME) caused by abiraterone.

Case Description

A 82-year-old male, with a past medical history of metastatic prostate cancer on treatment with leuprolide, abiraterone, and prednisone, presented with progressive weakness and falls. Prednisone was discontinued two months prior due to concerns for steroid myopathy. On examination he was hypertensive, delirious, and had diffuse weakness. Labs illustrated hypokalemia (K 1.7 mg/dl) and metabolic alkalosis (HCO3 34 mmol/L, pH 7.62). Additionally, he had suppressed aldosterone and renin levels with an elevated aldosterone/renin ratio of 60, high ACTH level, and low serum morning cortisol. These findings are consistent with the SAME secondary to abiraterone. The patient was treated with resumption of prednisone and initiated on eplerenone.

Discussion

Abiraterone suppresses testosterone production by inhibiting the 17-alpha-hydroxylase and C17,20-lyase enzymes. Consequently, cortisol production decreases, adrenocorticotropic hormone (ACTH) increases, and corticosterone increases, presenting as the SAME with hypokalemia, hypertension, and edema. Glucocorticoid administration with abiraterone inhibits ACTH and reduces corticosterone, thereby reducing the SAME risk. Eplerenone, a mineralocorticoid receptor antagonist, is the first-line treatment. Eplerenone avoids possible androgen receptor agonism, which can occur with spironolactone, and can be detrimental in treating metastatic prostate cancer.
Conclusion: Abiraterone is an effective steroidal inhibitor for castrate-resistant prostate cancer, but can lead to the SAME, which clinicians should be able to recognize and treat.