In 2021-2022, many more men globally will receive a potent AR inhibitor in either the metastatic hormone sensitive prostate cancer (mHSPC), non-metastatic castration resistant prostate cancer (nmCRPC), or mCRPC settings, with improved long term outcomes based on multiple positive phase 3 trials of abiraterone, enzalutamide, apalutamide, and darolutamide. This new form of maximal or combined androgen blockade in addition to ADT has extended survival, delaying symptomatic and metastatic progression, improving durable remissions based on PSA and imaging response criteria, major successes for our patients.
With first generation AR inhibitors such as flutamide and bicalutamide, prolonged responses to these therapies often led to anti-androgen withdrawal responses which were observed at progression after the patient stopped these agents. These withdrawal responses were due to point mutations in the ligand binding domains of the AR (such as T877A), turning these older agents into agonists that stimulated AR activity and PSA production. Withdrawal responses typically would last 3-6 months, but occasionally patients would experience prolonged withdrawal responses lasting over a year. However, the prevalence of withdrawal responses to stopping these novel AR inhibitors has not been well described.