A case of abiraterone acetate withdrawal syndrome after initiation of upfront abiraterone therapy for high‐risk prostate cancer

INTRODUCTION: Transient decrease in serum prostate‐specific antigen level can occur after abiraterone acetate withdrawal in male patient with metastatic castration‐resistant prostate cancer. Here, we report a case of abiraterone acetate withdrawal syndrome with transient prostate‐specific antigen decrease after progression to castration‐resistant disease while using upfront abiraterone therapy for high‐risk prostate cancer. CASE PRESENTATION: A 73‐year‐old man with hormone‐sensitive high‐risk prostate cancer with multiple bone metastases (prostate‐specific antigen level, 294.109 ng/mL) received upfront abiraterone/prednisolone combination and androgen deprivation therapy. One year later, prostate‐specific antigen level decreased to 0.017 ng/mL (nadir) but it gradually rose by 15 months after treatment initiation. He was diagnosed as castration‐resistant and new bone metastases appeared. After abiraterone was discontinued, prostate‐specific antigen level decreased and stabilized at a low level for 5 months. CONCLUSION: Abiraterone acetate withdrawal syndrome was observed when hormone‐sensitive prostate cancer with upfront abiraterone therapy progressed to castration‐resistant prostate cancer.