Fractionated Docetaxel and Radium 223 in Metastatic Castration-Resistant Prostate Cancer

Inclusion Criteria: 1. Histologically or cytologically confirmed adenocarcinoma of the prostate 2. Documented metastatic castration resistant disease with PSA progression, radiographic progression, or both, despite medical or surgical castration 3. Two or more bone metastases detected on skeletal scintigraphy 4. Eligible for docetaxel chemotherapy 5. ECOG Performance Status 0-2 6. Adequate organ function: 1. Hemoglobin \> 10 g/dL 2. Absolute Neutrophil Count ≥ 1,500 K/mL 3. Platelet count ≥ 150,000 x 10\^9/L 4. Total bilirubin ≤ 1.5x upper limit of normal range, excluding Gilbert syndrome 5. Serum AST ≤ 1.5 x upper limit of normal range 6. Serum ALT ≤ 1.5 x upper limit of normal range 7. Estimated glomerular filtration rate (GFR) \> 30mL/min 8. Ongoing castration (androgen deprivation therapy or prior orchiectomy) 9. Male subjects with female sexual partners of childbearing potential must agree to use at least one highly effective methods of birth control. 10. Ability to understand and willingness to sign an informed consent form prior to initiation of any study procedures. 11. Age ≥ 18 years Exclusion Criteria: 1. Prior radionuclide therapy for CRPC 2. Prior docetaxel for CRPC. (Permitted if given for castration sensitive disease \> 6 months prior). 3. Antiandrogen therapy within 4 weeks of enrollment. However, patients with primary failure of secondary anti-androgen therapy OR symptomatic progression, objective progression and/or biochemical evidence of rising PSA less than 4 weeks after discontinuation of anti-androgen therapy will not have anti-androgen withdrawal responses and will not be excluded. 4. Preexisting peripheral neuropathy grade 2 or higher. 5. Other serious medical condition as judged by the investigator. 6. Active second malignancy that requires therapy. 7. Known brain or leptomeningeal metastases 8. Concurrent enrollment in any other investigational anticancer therapy 9. Treatment with any myelosuppressive agent within 30 days of enrollment 10. Presence of bulky visceral metastases, defined as any of the following: 1. ≥ 4 lung lesions (at least 1cm each in size in the longest diameter) or pulmonary lymphangitic metastasis 2. Liver metastases with sum of lesion diameters totaling ≥ 5cm 11. Evidence of neuroendocrine or small cell differentiation on prior biopsy 12. History of severe hypersensitivity reactions to docetaxel or to drugs formulated with polysorbate 80