Exploratory FDG PET/CT Imaging in mCRPC Patients Treated with Sipuleucel-T ± IL-7: A Phase II Trial Subanalysis

Area of Science:

• Oncology
• Nuclear Medicine
• Immunotherapy

Background:

• Immunotherapy efficacy in metastatic castration-resistant prostate cancer (mCRPC) is limited.
• There is a need for noninvasive tools to monitor treatment-related biological changes in mCRPC.

Purpose of the Study:

• To evaluate exploratory metabolic imaging correlates using [18F]-FDG PET/CT in mCRPC patients undergoing sipuleucel-T (sip-T) immunotherapy.
• To assess tumor metabolic activity and potential immune-related metabolic changes during treatment.

Main Methods:

• A case series of three mCRPC patients from a sip-T clinical trial (CITN) was analyzed.
• Serial [18F]-FDG PET/CT imaging was performed at baseline and post-therapy.
• Imaging parameters included standardized uptake value (SUVmax, SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG).

Main Results:

• One patient showed progressive disease with increased MTV and TLG despite stable SUVmax.
• Another patient exhibited transient splenic metabolic increases post-sip-T.
• A third patient, treated with sip-T plus IL-7, demonstrated reduced SUVmax, stable disease, and decreased PSA, suggesting treatment response.

Conclusions:

• [18F]-FDG PET/CT imaging provides exploratory insights into metabolic changes in tumors and immune organs in mCRPC patients.
• Metabolic changes may reflect treatment-associated biological effects and potential immunotherapy response.
• Larger studies are needed to validate these preliminary findings in mCRPC.