Simultaneous multi-parametric dualtracer-PET/MRI for tumor characterization of primary prostate cancer

Objectives The classification of the primary tumor is, adjacent to the whole body staging, especially in prostate cancer of crucial significance, to decide between a radical approach or an "active surveillance" strategy. The potential of the multiparametric dt-PET/MRI is to be determined in this context.

Methods In so far 18 patients with biopsy confirmed prostate cancer PET/MRI was performed before scheduled radical prostatectomy. After application of 3 MBq / kg [¹⁸F]Fluormethylcholin (FMC), static PET (for 7 min.) was acquired 45 min. p.i. with simultaneous MRI followed by administration of 2 MBq/kg [⁶⁸Ga]-PSMA^HBED-CC (list mode for 50 minutes). MRI: T2w endorectal HR cor, ax, sag, 3D SPACE, DWI, DCE, partial body T2 HASTE cor, T1 VIBE KM fs tra. Semiquantitative PET and parametric MRI data was analyzed. In case of radical prostatectomy, histological whole mount sections were processed (3 mm), malignant and benign findings and Gleason patterns were digitally marked and compared with the imaging. P14/STAT3 microarrays for risk estimation of an increased metastatic invasion were determined from the main tumor areas.

Results 15 patients underwent radical prostatectomy, 3 were supplied to an extended therapeutic regimen due to a local T4-status and/or distant, PSMA-positive lesions. 14 patients (93%) were prospectively positive in the primary tumor focus in combined FMC/T2-weighted images and showed an SUV increase there after PSMA injection. Here, the FMC SUVmean correlated with the predominant Gleason pattern (AUC 0.9). 1 patient with tumor Focus <5mm and Gleason 3+3=6 was prospectively negative in both, PET and MRI. Tumor areas with loss of p14 and STAT3 showed significantly higher SUV (FMC) and decreased ADC values (p <0.05).

Conclusions In an ongoing evaluation in patients with biopsy confirmed prostate cancer, the multi-parametric FMC/PSMA-PET/MRI demonstrates a high potential for pre-therapeutic tumor characterization and simultaneous whole-body staging.