Low-Count Quantitative SPECT for Men Treated With Radium-223

Internal radiotherapies (radiolabeled molecules that are systemically administered and localize to sites of disease) provide cancer-ablating doses to diseased cells while sparing adjacent normal tissues. \[223Ra\]RaCl2 (Xofigo) is the first FDA-approved alpha-particle emitting radiopharmaceutical therapy (αRPT), providing a survival benefit for men with bone metastatic castration-resistant prostate cancer. Systemically administered radiotherapies distribute throughout the patient, accumulating to unknown levels at sites of disease and in radiosensitive vital organs. The whole-body distribution means that absorbed doses in the patient extend far beyond a pre-defined treatment field. There is a lack of information about αRPT distribution and localization, and this confounds treatment monitoring, complicates dose and schedule personalization, and impedes drug development. Single-photon emission computed tomography (SPECT) imaging offers a mechanism to quantify uptake; however, αRPT administered activities are significantly lower than those used with diagnostic procedures, which presents a challenge for quantitation with conventional methods. Preliminary research shows that low-count quantitative SPECT (LC-QSPECT) imaging demonstrates reliable quantitation of regional uptake for αRPTs. The purpose of this study is to demonstrate the feasibility, tolerability and performance of LC-QSPECT imaging.

Inclusion Criteria - Patients: * Histologically or cytologically confirmed castration-resistant prostate cancer with symptomatic bone metastases. * Minimum detectable skeletal lesion count of 3. * Eligible to receive Xofigo. * At least 18 years of age. * ECOG performance status ≤ 3. * Ability to understand and willingness to sign an IRB-approved written informed consent document. Legally authorized representatives may sign and give informed consent on behalf of study participants. Exclusion Criteria - Patients: * Predominant visceral metastatic disease. * Prior or concurrent malignancy whose natural history has the potential to interfere with the safety or efficacy assessment of the investigational regimen. Patients with prior or concurrent malignancy that does NOT meet that definition are eligible for this trial * Uncontrolled intercurrent illness including, but not limited to: ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, or cardiac arrhythmia. * Concurrent alternative radiopharmaceuticals * Inability to maintain stationary supine pose for 45-60 minutes Eligibility Criteria - Physicians: * Medical Oncologist or Radiation Oncologist at Siteman Cancer Center. * Treating patients with prostate cancer. * Willing to complete Physician Questionnaire during participation.