Changing the enzalutamide form from a capsule to a tablet improves the adherence of medicine intake: A case of a significant decrease in the prostate-specific antigen level and improvement in radiographic findings.

INTRODUCTION:In June 2018, enzalutamide began to be sold in a tablet form in Japan and Germany. We herein report the case of an improvement in prostate cancer progression due to changing enzalutamide dosage form from a capsule to a tablet. CASE PRESENTATION:A 76-year-old man was initially referred to our hospital for the further examination of his elevated prostate-specific antigen level (3664.0 ng/mL). He had developed castration-resistant prostate cancer 10 months after initial treatment. Treatment with enzalutamide (capsule form) was subsequently initiated. In June 2018, drug form of enzalutamide was changed from a capsule to a tablet. After switching to an enzalutamide tablet, his prostate-specific antigen level decreased significantly from 493.0 to 26.5 ng/mL. CONCLUSION:While the reason for this prostate-specific antigen response is unclear, changing the enzalutamide form from a capsule to a tablet may have improved the adherence of drug intake and thereby resulted in castration-resistant prostate cancer control.