Metabolic Volumetric Parameters in C-Choline PET/MR Are Superior PET Imaging Biomarkers for Primary High-Risk Prostate Cancer.

Purpose: Positron emission tomography/magnetic resonance imaging (PET/MRI) can facilitate the use of noninvasive imaging biomarkers in clinical prostate cancer staging. Although multiparametric MRI is a widely used technique, the clinical value of simultaneous PET imaging remains unclear. This study aimed at investigating this issue.

Methods: Between January 2015 and December 2016, 31 high-risk prostate cancer patients underwent C-choline PET/MRI for staging purposes. Clinical characteristics and imaging parameters, including the standardized uptake value (SUV) and metabolic volumetric parameters from PET imaging; apparent diffusion coefficient (ADC) values from diffusion-weighted imaging; and volume transfer rate constant (Ktrans), reflux rate constant (Kep), and initial area under curve (iAUC) in 60 seconds from dynamic contrast-enhanced (DCE) MRI were analyzed.

Results: C-Choline PET imaging parameters were significantly correlated with prostate-specific antigen (PSA) levels, and metabolic volumetric parameters, including metabolic tumor volume (MTV) and uptake volume product (UVP), showed significant correlations with other MRI parameters. In our cohort analysis, the PET/MRI parameters UVP/minimal ADC value (ADC) and kurtosis of Kep (Kep)/ADC were significant predictors for progression-free survival (PFS) (HR = 1.01, 95% CI: 1.00-1.02, =0.031 and HR = 1.09, 95% CI: 1.02-1.16, =0.009, respectively) in multivariate Cox regression analysis. High UVP/ADC and Kep/ADC values were significantly associated with shorter PFS.

Conclusions: Metabolic volumetric parameters such as MTV and UVP can be routinely used as PET imaging biomarkers to add prognostic value and show better correlations in combination with MR imaging parameters in high-risk prostate cancer patients undergoing C-choline PET/MRI.