Bone metastatic castration-resistant prostate cancer

Inclusion Criteria

- Participants who have histologically confirmed adenocarcinoma of the prostate.
 - Participants with bone metastatic CRPC, progressing after 1 or 2 prior lines of systemic treatment for metastatic prostate cancer (including prior treatment for metastatic hormone sensitive prostate mHSPC or metastatic castration resistant prostate cancer mCRPC).
 - Participants with at least 2 bone metastases on Tc 99m phosphonate whole body planar bone scans at Screening.
 - Documented progression of mCRPC. Disease progression is defined by at least one of the following criteria: a. PCWG3 criteria (defined as 2 consecutive increases in PSA over a previous reference value measured at least one week prior, with a minimal start value of 1.0 ng/mL) or b. ≥2 new bone lesions (according to PCWG3 bone scan criteria) or c. Radiological progression according to RECIST, version 1.1.
 - Ability to participate in the required study procedures including all scanning procedures and ability to control pain to ensure tolerance and completion of the necessary scanning procedures.
 - Maintenance of medical castration or surgical castration with testosterone less than 50 ng/dL (1.7 nmol/L). If the participant is being treated with luteinizing hormone releasing hormone (LHRH) agonists or antagonists (participant who has not undergone orchiectomy), this therapy must have been initiated at least 4 weeks prior to start of Screening and must be continued throughout the study.
 - Participants must be on a bone health agent prior to the first dose of radium-223 dichloride. Participants with at least 6 months of prior bone health agent (BHA) treatment are preferred.
 - Eastern Cooperative Oncology Group performance status (ECOG PS) 0 or 1.
 - Life expectancy ≥6 months.

Exclusion Criteria

-  Any chronic medical condition requiring continuous systemic corticosteroid treatment at a higher dose than 5 mg prednisone / prednisolone twice daily. 
 - Pathological finding consistent with neuroendocrine features small cell carcinoma of the prostate. 
 - Metastatic bone deposits extend of disease (EOD) grades 0 or 4 (according to centrally assessed Tc 99m phosphonate planar bone scans during Screening). 
  - History of visceral metastasis, or presence of visceral metastasis detected by screening imaging examinations (according to central review at screening). 
 - Other malignancy treated within the last 5 years (except non-melanoma skin cancer or low-grade superficial bladder cancer). 
 - Imminent spinal cord compression based on clinical findings and / or magnetic resonance imaging (MRI).  - Participants with history of spinal cord compression should have completely recovered. 
 - Active or symptomatic viral hepatitis 
 - Inability to tolerate any of the other imaging procedures in the study (ie, bone SPECT/CT and planar bone scans with a Tc 99m phosphonate radiotracer, DXA scan, radium-223 SPECT/CT scans). 
 - Any condition, which in the opinion of the investigator would preclude participation in this trial. 
 - Hypersensitivity to radium-223 dichloride. 
 - Blood transfusion or erythropoietin stimulating agents 4 weeks prior to start of Screening and during the whole Screening period before enrollment into the cohort. 
 - Prior administration of an investigational therapeutic for CRPC.