The 4Kscore® Test (OPKO Diagnostics, Woburn, MA, USA) or the four-kallikrein panel is a commercially available prebiopsy blood test that is used in combination with clinical information (i.e., age, race, DRE, PSA, and family history) for predicting the risk of aggressive PCa after a biopsy is performed [64]. Here, KLK4 is linked to posterior cortical atrophy.