This patient, who has recurrent prostate cancer metastatic to bone, should be treated with the radiopharmaceutical agent radium-223. Patients with metastatic prostate cancer who are found to have a biochemical recurrence (a rising serum prostate-specific antigen level and no evidence of local disease progression) will typically respond to androgen deprivation therapy. However, they will also eventually develop clinical metastatic disease. Once this occurs, optimal management depends on multiple factors, including the extent and sites of metastases and the symptoms associated with the disease. One important consideration in this setting is use of a bone-seeking radiopharmaceutical agent. These agents concentrate in bone, and recent data indicate radium-223 is associated with improvement in both symptoms and overall survival. Radium-223 is indicated specifically for patients with bone-limited or bone-predominant symptomatic metastatic disease, such as that present in this patient.

Bilateral orchiectomy, while a very effective form of antiandrogen therapy, would not be indicated in a patient who has already been demonstrated to be castrate resistant.

Estrogen therapy has uncertain benefit in the treatment of castrate-resistant prostate cancer, and would not be considered an appropriate treatment option for this patient, especially given that radium-223 has been associated with both improved survival and symptom burden.

External-beam radiation to metastatic sites can be considered for treatment of patients with spinal cord compression or for those with focal symptomatic bone metastases, neither of which this patient has.