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.

NCT Number	NCT07221825
Lead Sponsor	Washington University School of Medicine Collaborators: National Institute for Biomedical Imaging and Bioengineering (NIBIB)
Conditions	Prostate Cancer, Cancer of the Prostate
Enrollment	38 participants
Start Date	2026-09-01
Primary Completion	2028-04-30 (estimated)
Study Completion	2028-07-31 (estimated)
Updated on ClinicalTrials.gov	2026-07-21