(UroToday.com) The availability of multiple treatments for metastatic castration-resistant prostate cancer (mCRPC) mandates the need to identify, as well as validate, prognostic and predictive factors applicable to clinical practice. Given the complexity of therapeutic decision-making in these patients, there is a need to determine which patients would be most likely to benefit from a given treatment more rapidly and facilitate optimized decisions on therapeutic sequencing. PSA value is widely used for the monitoring of treatment outcome in mCRPC in the clinical real-world setting. Early PSA changes are not considered in the definition of PSA progression due to the potential for spurious “flare” reactions. The early identification of mCRPC patients not benefiting from enzalutamide or abiraterone could be of paramount importance for optimal treatment delivery and cost-effectiveness. At the ASCO 2021 annual meeting, Dr. Fernando López-Campos and colleagues from Spain evaluated the significance of an early PSA increase in mCRPC patients treated with enzalutamide or abiraterone.