Antiandrogen Withdrawal Syndrome After Discontinuation of Enzalutamide in Patients With Metastatic Castration-Resistant Prostate Cancer: A Report of Two Clinical Cases and a Literature Review.

Metastatic prostate cancer treatment is based on androgen deprivation, with pharmacological or surgical castration. This treatment may be complemented with the addition of antiandrogenic drugs. In the setting of prostate-specific antigen (PSA) progression and subsequent suspension of the antiandrogenic drug, there might occur a phenomenon of antiandrogen withdrawal, leading to a decrease in PSA and/or improvement in imaging or clinical outcomes after discontinuation of the antiandrogenic agent. Although there are some descriptions of withdrawal after the cessation of enzalutamide, the physiological mechanism behind it, as well as its frequency and impact on patient survival, remain unknown. We present two clinical cases of antiandrogenic withdrawal after enzalutamide discontinuation and discuss potential contributing factors to this phenomenon.