- Castration resistant disease defined as evidence of radiological and/or PSA progression despite castrate levels of testosterone (serum testosterone < 50 ng/dL (1.7 nmol/L)). For PSA progression, there must be at least 2 sequential rises at a minimum of 1-week intervals. The first PSA value must be ≥ 2. (Prostate Cancer Working Group 2 (PCWG2) criteria)