We identified 26,548 men initially managed with AS aged <80 years, with clinically localized prostate cancer (cT1-2cN0M0), PSA ≤ 20 ng/mL, biopsy GG ≤ 2 with percent positive cores ≤33% and who converted to treatment with radical prostatectomy from the surveillance, epidemiology, and end results prostate with the watchful waiting database. This evidence concerns the gene KLK3 and prostate carcinoma.