Older studies in animals and humans have shown cancer responses to very low doses of whole-body or hemi-body radiation. To study the effects of low doses of radiation in patients with recurrent prostate cancer, investigators will enroll up to 21 patients for 10 fractions of low dose radiation, delivered over 5 weeks. Participants will be followed on study for 12 months, capturing PSA, CBC, QoL and blood samples for immunological analysis.

Inclusion Criteria:

• A confirmed diagnosis of prostate cancer.
• Having undergone prior prostate surgery or radiotherapy or both.
• Evidence of recurrence of the disease as demonstrated by rising PSA levels. Patients are eligible if on androgen blockade or hormone naïve.

Exclusion Criteria:

• Prior treatment with chemotherapy and/or abiraterone and/or enzalutamide and/or radium-223.
• Receiving treatment with immunosuppressive medications.
• Platelet count below 50,000/µl (50 x 109/l) or leukocyte count below 3,000/µl (3 x 109/l) or granulocyte count below 2,000/µl (2 x 109/l).
• Other medical conditions or co-morbidities which, in the opinion of the Investigator, may interfere with the participant's ability to participate in the study.
• Language difficulties which may hinder the patient's ability to complete the trial.
• Inability of the potential participant to provide consent.
• Lack of independence in daily living activities and any other conditions which, in the opinion of the Investigator, will hinder the participant's ability to participate and complete the study obligations.

No plan to share IPD. Results to be reported as aggregate outcomes for the group.