Successful adoption of focal therapy for the treatment of prostate cancer will hinge on several critical issues: 1) can we accurately identify index lesions within the prostate, 2) can we reliably image cancers within the prostate, 3) long-term efficacy of the technology to eradicate cancer, 4) appropriate follow-up of patients treated with focal therapy, and 5) limitations of PSA following therapy and how to detect recurrent/persistent disease. The gene discussed is KLK3; the disease is prostate cancer.