Abstract Prostate cancer is generally known as cancer with a good prognosis, and even in metastatic cases, the 10-year survival rate in Japan is around 38%. Since gene mutations constantly change over a relatively long course of treatment, the clinical utility of Liquid Biopsy, which can evaluate mutations from cancer cells in the blood, is attracting clinical attention. As a result of analysis using a next-generation sequencer, the most frequent mutation is androgen receptor amplification (AR Amp), followed by P53 mutation and PTEN mutation. Based on the above background, the prognostic significance of AR Amp was studied in 102 samples (38 cases) of Cell-free DNA (cfDNA) derived from prostate cancer patients treated at our institution. As a result of performing multivariate analysis including PSA, a clinical marker of prostate cancer, AR Amp predicts independently over PSA in progression-free survival (PFS) and overall survival (OS). In prostate cancer, in addition to AR, DNA repair gene mutations such as BRCA and ATM have been found around 10%, and in cases with BRCA deletion, PARP inhibitors have been reported to prolong the prognosis by six months. In cases of prostate cancer with a high degree of microbial instability(MSI-H), although as low as around 2% of the total prostate cancer patients, the immune checkpoint inhibitor showed a decent response. Currently, the risk classification of prostate cancer is determined based on the pathological grade (Gleason Score), PSA, size of the metastatic lesion (High Volume). However, the time will come to choose the treatment policy based on new risk classification includes the genome information.