Based on the prostate specific antigen (PSA) level, biopsy Gleason score, and American Joint Commission on Cancer tumor (T) category, approximately 10%–50% of men will have evidence of disease recurrence at 10 years following external beam radiation therapy with or without concurrent androgen deprivation therapy (ADT) for prostate cancer [1, 2]. The gene discussed is KLK3; the disease is prostate cancer.