According to current clinical definitions, indolent prostate cancer is considered a low-risk (Gleason score ≤ 6, cT1c-cT2a, PSA ≤ 10 ng/mL) or very low-risk disease (Gleason ≤ 6, cT1c, PSA density ≤ 0.15 ng/mL/mg, involvement of ≤2 cores with ≤50% of each core, including the non-neoplastic intermediate segments) [17]. Here, KLK3 is linked to prostate cancer.