18F-PSMA 1007 PET/CT Metrics for Assessment of Whole- Body Tumor Burden in Patients with Metastatic Prostate Cancer

Background: Conventional assessment based solely on standardized uptake
values (SUVs) of individual lesions may inadequately reflect the total tumor
burden in patients suffering from metastatic prostate cancer (PCa). Prostate-
specific membrane antigen (PSMA)-targeted PET/CT imaging enables the
derivation of quantitative volumetric biomarkers that simultaneously reflect
lesion volume, number, and metabolic activity.
Objective: Our objective was to validate PSMA-total volume (PSMA-TV) and
-total lesion (PSMA-TL) as quantitative volumetric biomarkers for whole-body
tumor burden in metastatic PCa and assess their relation to PSA and Gleason
score (GS) to enhance risk stratification and disease monitoring.
Patients and Methods: Thirty-nine individuals with PSMA-positive metastatic
PCa were included. Quantitative PET/CT parameters were computed from all
probable pathological lesions, encompassing SUVmean, SUVmax, and PSMA-
TV/PSMA-TL. Correlations among imaging biomarkers, PSA levels, and GS
were examined.
Results: Whole-body PSMA parameters exhibited significant moderate
relationships with PSA levels (SUVmax: r = 0.55, p = 0.001; SUVmean: r =
0.60, p < 0.001; PSMA-TL: r = 0.60, p < 0.001). Nonetheless, there was a weak
association with PSMA-TV: r = 0.31, p = 0.05. Furthermore, PSMA-derived
metrics exhibited significant moderate correlations with GS (SUVmax: r = 0.40,
p = 0.03; PSMA-TV: r = 0.40, p = 0.02; PSMA-TL: r = 0.40, p = 0.006),
whereas a weak correlation with SUVmean: r = 0.30, p = 0.046;
Conclusion: Both PSMA-TV/PSMA-TL serve as potential quantitative imaging
biomarkers for the volumetric evaluation of tumor burden in metastatic PCa.
These measures offer significant insight into intra-lesional PSMA expression
and systemic disease activity.