Prostate-specific antigen (PSA) testing has been widely used for the diagnosis of prostate cancer, but there is a concern that an over-reliance on PSA as a screening tool could led to an over-diagnosis of low-risk prostate cancer, and subsequent over-treatment of patients with low-to-intermediate risk cancer undergoing conventional radical treatments using radiation therapy or prostatectomy, both of which carry a significant risk of side-effects.1 The gene discussed is KLK3; the disease is cancer.