KLK3 and prostate cancer: Anti-1-amino-3-[18F]-fluorocyclobutane-1-carboxcylic acid (18F-fluciclovine; Axumin®, Blue Earth Diagnostics Ltd., Oxford, UK) is an artificial amino acid-based positron emission tomography (PET) radiotracer approved by the U.S. Food and Drug Administration and the European Medicinal Agency for the detection of local recurrence and metastases in patients with prostate cancer and rising blood level of prostate-specific antigen (PSA) after initial radical treatment [1].