PRIMARY OBJECTIVE:~I. To evaluate the efficacy of tin-117m diethylenetriaminepentaacetic acid (Sn-117m-DTPA) on sustained pain response in patients with castration-resistant prostate cancer (CRPC) metastatic to at least two bone sites with at least one clinically meaningful pain at baseline (>= 4 on an 11-point pain intensity scale).~SECONDARY OBJECTIVES:~I. To assess the safety and tolerability of Sn-117m-DTPA per Common Terminology Criteria for Adverse Events (CTCAE) version (v)5.0.~II. To measure Sn-117m-DTPA activity by gamma-camera dosimetry scans (serial full body planar images) obtained at 1 hour, 4 hours (or within 4-6 hours), 24 hours (or within 16-24 hours), 48 hours (or within 36-48 hours), 72 hours (or within 60-72 hours), 1 week (+/- 2 days), and 4 weeks (+/- 2 days) after the first Sn-117m-DTPA administration.~III. To evaluate the therapeutic efficacy of Sn-117m-DTPA at 24 weeks as measured by Prostate Cancer Working Group 3 (PCWG3) criteria.~IV. To evaluate time to the first symptomatic skeletal event defined as i) the first use of external-beam radiation therapy to relieve skeletal symptoms; ii) new symptomatic pathologic vertebral or nonvertebral bone fractures; iii) spinal cord compression; or iv) tumor-related orthopedic surgical intervention.~V. To evaluate the overall pain response rate at 24 weeks. VI. To evaluate the duration of pain response defined as from the time of improvement in pain response (pain index =< 3) until the pain recurs.~VII. To measure changes and time to progression in serum prostate-specific antigen (PSA) and serum alkaline phosphatase (ALP) levels.~VIII. To measure patient-reported outcomes (PROs) and adverse events (AEs) (PRO-CTCAE) captured by digital instruments.~IX. To evaluate progression-free survival (PFS) and overall survival (OS).~EXPLORATORY OBJECTIVES:~I. To examine any tumor genomic alterations that may be associated with response or resistance to Sn-117m-DTPA, a radiopharmaceutical agent.~II. To examine the changes in systemic inflammatory markers (such as interferon [IFN]-gamma, tumor necrosis factor [TNF]-alpha, interleukins [IL]-8, IL-10, and IL-17) by flow cytometry, and changes in markers of immune function by measuring the percentage and absolute number of CD4+ T helper cells, CD8+ T cytotoxic cells, T regulatory cells, polymorphonuclear (PMN) myeloid-derived suppressor cells (MDSCs), and mononuclear MDSCs (M-MDSCs) prior to treatment versus (vs.) end of cycle 1, end of cycle 2, and at week 24 and correlate values and/or changes with treatment outcomes.~III. To evaluate the feasibility of measuring polo-like kinase 1 (Plk1) expression via immunohistochemistry (IHC) staining on archival tissues.~OUTLINE:~Patients receive tin Sn 117m DTPA intravenously (IV) over 5-10 minutes on day 1. Treatment repeats every 8 weeks for 2 cycles in the absence of disease progression or unacceptable toxicity. Patients may receive tin Sn 117m DTPA for an additional 2 cycles if pain recurs within 6 months after a 16-week pain observation period and no disease progression on bone scans, or evidence of clinical progression.~After completion of study, patients are followed up every 4 weeks until week 28, and then every 3 months for up to 12 months after the first dose of tin Sn 117m DTPA.
This phase II trial studies the effect of Sn-117m-DTPA on bone pain in patients with prostate cancer that has spread to the bones. Sn-117m-DTPA is a radioactive therapeutic agent that localizes to bones when given to patients. Sn-117m-DTPA may help reduce bone pain in patients with prostate cancer that has spread to the bones.