Exploring Spatial-Temporal Changes in ¹⁸F-Sodium Fluoride PET/CT and Circulating Tumor Cells in Metastatic...

Area of Science:

• Oncology
• Nuclear Medicine
• Radiology

Background:

• Intrapatient treatment response heterogeneity is often overlooked.
• Quantitative total bone imaging (QTBI) using 18F-NaF PET/CT enables assessment of interlesional treatment response heterogeneity in bone.
• Understanding spatial-temporal response is crucial for identifying patients who may benefit from treatment beyond progression.

Purpose of the Study:

• To characterize interlesional treatment response heterogeneity in bone using QTBI in men with progressive metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide.
• To evaluate the spatial-temporal response of bone lesions to enzalutamide therapy.

Main Methods:

• Twenty-three men with progressive mCRPC and bone lesions were treated with enzalutamide.
• 18F-NaF PET/CT scans were acquired at baseline (PET1), week 13 (PET2), and at progression (PET3).
• QTBI was employed to assess lesion-level treatment response, with the primary endpoint being the proportion of men with at least one responding bone lesion at PET3.

Main Results:

• Global standardized uptake value (SUV) metrics generally decreased during enzalutamide treatment and increased at progression.
• Change in SUVhetero (PET1 to PET3) was the strongest predictor of prostate-specific antigen (PSA) progression (hazard ratio, 3.88).
• All evaluable patients (22/22) demonstrated at least one responding bone lesion at PET3, indicating sustained benefit beyond progression.

Conclusions:

• A low proportion of bone lesions progressed, suggesting many lesions continue to benefit from enzalutamide beyond documented progression.
• Selective targeting of nonresponding lesions could be a viable strategy to prolong treatment benefit in mCRPC.
• QTBI is a valuable tool for assessing treatment response heterogeneity in bone metastases.