As previously stated, successfully adoption of focal therapy for the treatment of prostate cancer will hinge on two critical issues: 1) accurately identifying index lesions within the prostate, 2) reliably imaging cancers within the prostate, 3) long-term efficacy of the technology to eradicate cancer, 4) appropriate follow-up of patients treated with focal therapy, 5) limitations of PSA following therapy and how to detect recurrent/persistent disease. This evidence concerns the gene KLK3 and prostate cancer.