KLK3 and neoplasm: In a seminal study by Antonarakis et al., the detection of AR-V7 on circulating tumor cells (CTCs) was associated with dismal responses to both ENZ and ABI: a 0% prostate-specific antigen (PSA) response rate and a median PSA progression-free survival (PSA-PFS) of little over 1 month in both groups, with a hazard ratio for PSA progression of 7.4 in the ENZ cohort and 16.1 in the ABI cohort [12].