Circulating Tumor DNA (ctDNA) Monitoring in the Assessment and Prediction of the Efficacy of PARP Inhibitors (PARPi)

Inclusion Criteria: Patients must meet ALL of the following criteria: 1. Willing and able to provide informed consent. 2. Adult males from 18 to 75 years age. 3. History of histologically or cytologically confirmed adenocarcinoma of the prostate with Homologous Recombination Deficiency or DDR genes mutation (BRCA1/2, ATM, BARD1, BRIP1, CDK12, CHEK1, CHEK2, FANCL, PALB2, PPP2R2A, RAD51B, RAD51C, RAD51D, RAD54L) detected by high throughput sequencing 4. Documented evidence of metastatic castration resistant prostate cancer (mCRPC) and proposed treatment of PARP inhibitors. 5. Evidence of measurable target lesion in imaging studies. 6. Participants can provide adequate formalin fixed paraffin-embedded (FFPE) tumor tissue collected before any treatment: tumor cell content\>30% and necrotic cells\<10%. 7. ECOG performance status 0-1 8. Estimated survival≥12 weeks Exclusion Criteria: Patients must NOT meet any of the following criteria: 1. Do not meet the inclusion criteria. 2. Under any other anti-tumor therapy like chemotherapy and/or immunotherapy. 3. Receiving organ transplantation in the last 3 months. 4. Participants with autoimmune diseases or history of HBV, HCV or HIV infection (acute or chronic). 5. Participants with pneumonia. 6. Severe concurrent illness or co-morbid disease that would make the subject unsuitable for enrolment 7. Unwilling and unable to provide informed consent. 8. Patients who are judged unsuitable for clinical trial participation by the investigators. Elimination Criteria: Violation of the prescribed rule of medication that may influence the judgment of curative effect and safety.