The aim of this study is to evaluate the efficacy of 2 cycles of combinatory adebrelimab and stereotactic radiotherapy, followed by monotherapy adebrelimab in patients with metastatic castration-resistant prostate cancer. Dr. Yao Zhu from Fudan University Shanghai Cancer Center is the co-leading PI of this study.

Inclusion Criteria:

1. Male with 18-75 years of age at the time consent form is signed
2. The patient must have histologically or cytologically confirmed prostate adenocarcinoma, which has been determined to be metastatic prostate cancer based on routine imaging assessment (bone scan or CT/MRI);
3. The patient has assessable visceral metastases or soft tissue lesions (outside the pelvis), and the patient should undergo image-guided lesion puncture before medication if considered safe assessed by the PI;
4. Disease progression after treatment with ≥1 androgen-receptor (AR) targeted therapies (such as abiraterone acetate, enzalutamide, apalutamide, darolutamide, etc.);
5. Disease progression after treatment with ≥1 line of taxane-based chemotherapy or intolerant to chemotherapy;
6. The patient shows PSA progression (defined as an increase in PSA levels at least twice consecutively, with an interval of at least one week between assessments, and a PSA value of ≥1 ng/mL at screening), or according to RECIST 1.1 criteria, imaging progression of soft tissue disease with or without PSA progression, or bone lesion progression according to PCWG3 standards: bone scan reveals ≥2 new bone lesions;
7. The patient needs to maintain effective and continuous treatment with luteinizing hormone-releasing hormone analogs (LHRHa) throughout the study treatment, or has undergone orchiectomy; and serum testosterone levels must be maintained at castration level（<50 ng/dL）；
8. Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0-2;
9. Expected survival ≥6 months;
10. Normal bone marrow function: absolute neutrophil count ≥1.5×10^9/L; platelets ≥75×10^9/L; hemoglobin ≥90g/L; white blood cell count ≥3.0×10^9/L;
11. Normal liver function: alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≤2.5 times the upper limit of normal (ULN); for patients with liver metastases, ALT/AST may be ≤5 times ULN
12. Total bilirubin ≤1.5 times ULN or total bilirubin &gt;1.5 times ULN and direct bilirubin ≤ULN;
13. Normal coagulation function: INR ≤1.5, partial thromboplastin time (APTT) ≤1.5 times ULN, prothrombin time (PT) \