The criteria for disease progression when using changes in PSA is defined by the Prostate Cancer Clinical Trials Working Group (PCWG2) [6] and the Prostate-Specific Antigen Working Group (PSAWG) [7], and has been validated by the data-sets from two large Southwest Oncology Group Trials (SWOG 9346 and 9916) [8]. The gene discussed is KLK3; the disease is prostate cancer.