If clinically localized PCa patient’s TNM staging is T1c for Primary Tumor(T), Gleason score ≤ 6, PSA < 10 ng/ml, fewer than 3 prostate biospy cores positive and ≤50% cancer in each core, PSA density < 0.15 ng/ml/g, the patient can be grouped into the very low risk group. This evidence concerns the gene KLK3 and cancer.