Inclusion Criteria:  Diagnosed with metastatic prostate cancer (hormone sensitive or castrate resistant) and histologically confirmed Metastatic at disease onset or relapsed disease A treatment decision has been made to start a course of docetaxel as part of their standard of care treatment in accordance with the drug's label and the treating clinician's judgement Patient has not received a previous cycle of docetaxel within 8 weeks of the date of enrolment Life expectancy > 12 weeks Participant is willing and able to give informed consent for participation in the study  Exclusion Criteria:  - Patients with autoimmune disease receiving active treatments Participant is unable to give informed consent