Enzalutamide-induced severe thrombocytopenia complicated by a seizure in a 76-year-old man with castration-resistant prostate cancer

Introduction: Adverse events with enzalutamide widely used for men with castration-resistant prostate cancer are of interest.

Case presentation: A 76-year-old man developed castration-resistant prostate cancer. He received 160 mg of enzalutamide daily. On the 13th day after treatment, severe thrombocytopenia was observed (platelet count: 1.9 × 10⁴/μL). Normal coagulation and fibrinolytic systems suggested thrombocytopenia induced by enzalutamide. Enzalutamide was withdrawn immediately, and platelet count uneventfully recovered to 7.0 × 10⁴/μL and 28.8 × 10⁴/μL 9 and 30 days after discontinuation, respectively. He restarted enzalutamide therapy without thrombocytopenia recurrence. However, 81 days after restarting enzalutamide, he experienced a seizure. There were no significant findings from brain computed tomography, which suggested that the seizure was also an enzalutamide-associated adverse event.

Conclusion: Thrombocytopenia may occur early following enzalutamide therapy, and blood analysis within 2 weeks after treatment may facilitate its management. Enzalutamide-induced thrombocytopenia, complicated by seizure, has not been reported.

Keywords: castration‐resistant prostate cancer; enzalutamide; seizure; severe adverse event; thrombocytopenia.