According to the guidelines of the European Society of Urology (EAU) AS can be offered to patients with the lowest risk of cancer progression implicating clinical stage T1-2a, PSA < 10 ng/mL, biopsy GS≤ 6 (at least 10 biopsy cores), ≤2 positive biopsies as well as minimal biopsy core involvement (≤ 50% cancer per biopsy) [4]. This evidence concerns the gene KLK3 and cancer.