Prospective research of Natural Killer cells as predictive biomarkers to stratify patients likely to have longer response time to castration.

The main objective is to validate prospectively the results of a retrospective study showing a correlation between the level of NKp30 and NKp46 receptor-activators expression on the surface of NK cells and 1) the survival time, 2) the response time to castration in patients with metastatic prostate cancer.

Prospective monocenter, open-label study.

During a visit in the frame of management of the disease, a single blood sample will be collected. Patients will then have a standard care follow-up for a period of 5 years. Follow up data (death, progression) will be collected every 6 months.

Inclusion Criteria:

1. Patient with metastatic prostate cancer.
2. Aged of 18 years or more.
3. Patient in period of sensitivity to castration (patient non castrated or castration performed less than 1 year ago) and lack of progression.
4. Patient having signed an informed consent.
5. Patient affiliated to the national "Social Security" regimen or beneficiary of this regimen.

Exclusion Criteria:

1. Patient under chemotherapy treatment at the time of sampling
2. Patient under corticotherapy treatment at the time of sampling
3. Patient in emergency situation, adult subject to a measure of legal protection (placed under judicial protection, tutorship, or curatorship), or unable to give consent.
4. Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study medical follow-up
5. Contraindications to study procedure