High-risk prostate cancer is defined by the National Comprehensive Cancer Network (NCCN) as disease with a serum prostate-specific antigen (PSA) level greater than 20 nanograms per milliliter (ng/mL; to convert to μg/L, multiply by 1), a clinical T category 3 or 4, or a Gleason grade group 4 or 5.1 Radiation therapy with long-term androgen deprivation therapy (ADT) is an effective standard of care treatment in this setting. This evidence concerns the gene KLK3 and prostate carcinoma.