In this study, the investigators aim to establish the prostate cancer active surveillance prospective cohort in our institution, and finally investigate the 5 year rates of reclassification during active surveillance as the primary endpoint of the current study.

Prostate cancer (PCa) remains one of the most commonly diagnosed malignancies in men worldwide. Early diagnosis and definitive therapy seem to improve oncological outcomes in men with high-risk disease, but significant concerns exist in terms of the overdiagnosis and overtreatment of patients with lower-risk tumors. In this context, active surveillance (AS) has recently emerged as a alternative treatment strategy in PCa patients with low risk cancers. However, published data are based on Western population with different protocol, and therefore; well-controlled data with well-organized and prospective cohort are urgently needed in Korean patients with low-risk PCa because Korean patients have significantly different tumor characteristics compared to Western patients. Here, the investigators have a plan to establish the Seoul National University Enrolled Registry for Prostate Cancer with Active Surveillance, and finally provide the concrete evidence for the clinical outcomes of active surveillance program as the primary therapeutic strategy for low-risk PCa in Korean men.

Inclusion Criteria:

1. Men < 80 years
2. Pathologically proven adenocarcinoma of the prostate by transrectal prostate biopsy ≥ 10 cores
3. Pre-Bx PSA ≤ 10ng/ml
4. PSA density < 0.15ng/ml/ml
5. Clinical stage T1-2a
6. Biopsy Gleason score ≤ 6
7. No. of positive cores ≤ 2
8. Maximum cancer involvement in any one core ≤ 20%.
9. No PIRADS 5 lesion on multiparametric prostate MRI (1.5T or 3T)
10. Participants must be willing to attend the follow-up visits - T1a-b disease should be confirmed by systematic TRUS-Bx ≥ 10 cores

Exclusion Criteria:

1. A former therapy for prostate cancer.

Korean men with pathologically proven adenocarcinoma of prostate cancer with low-risk who will be treated by active surveillance protocol in Seoul National University Hospital.