Comparison of hybrid (68)Ga-PSMA PET/MRI and (68)Ga-PSMA PET/CT in the evaluation of lymph node and bone metastases of prostate cancer.
OBJECTIVE
To evaluate the reproducibility of the combination of hybrid PET/MRI and the (68)Ga-PSMA-11 tracer in depicting lymph node (LN) and bone metastases of prostate cancer (PC) in comparison with that of PET/CT.


METHODS
A retrospective analysis of 26 patients who were subjected to (68)Ga-PSMA PET/CTlow-dose (1 h after injection) followed by PET/MRI (3 h after injection) was performed. MRI sequences included T1-w native, T1-w contrast-enhanced, T2-w fat-saturated and diffusion-weighted sequences (DWIb800). Discordant PET-positive and morphological findings were evaluated. Standardized uptake values (SUV) of PET-positive LNs and bone lesions were quantified and their morphological size and conspicuity determined.


RESULTS
Comparing the PET components, the proportion of discordant PSMA-positive suspicious findings was very low (98.5 % of 64 LNs concordant, 100 % of 28 bone lesions concordant). Two PET-positive bone metastases could not be confirmed morphologically using CTlow-dose, but could be confirmed using MRI. In 12 of 20 patients, 47 PET-positive LNs (71.9 %) were smaller than 1 cm in short axis diameter. There were significant linear correlations between PET/MRI SUVs and PET/CT SUVs in the 64 LN metastases (p < 0.0001) and in the 28 osseous metastases (p < 0.0001) for SUVmean and SUVmax, respectively. The LN SUVs were significantly higher on PET/MRI than on PET/CT (p SUVmax < 0.0001; p SUVmean < 0.0001) but there was no significant difference between the bone lesion SUVs (p SUVmax = 0.495; p SUVmean = 0.381). Visibility of LNs was significantly higher on MRI using the T1-w contrast-enhanced fat-saturated sequence (p = 0.013), the T2-w fat-saturated sequence (p < 0.0001) and the DWI sequence (p < 0.0001) compared with CTlow-dose. For bone lesions, only the overall conspicuity was higher on MRI compared with CTlow-dose (p < 0.006).


CONCLUSIONS
Nodal and osseous metastases of PC are accurately and reliably depicted by hybrid PET/MRI using (68)Ga-PSMA-11 with very low discordance compared with PET/CT including PET-positive LNs of normal size. The correlation between PET/MRI SUVs and PET/CT SUVs was linear in LN and bone metastases but was significantly lower in control (non-metastatic) tissue.
Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany. m.freitag@dkfz.de.
Martin T
MT
Freitag
Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.|Department of Urology, University Hospital Heidelberg, Heidelberg, Germany.
Jan P
JP
Radtke
Department of Urology, University Hospital Heidelberg, Heidelberg, Germany.
Boris A
BA
Hadaschik
Department of Bioinformatics and Statistics, German Cancer Research Center, Heidelberg, Germany.
A
A
Kopp-Schneider
Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
Matthias
M
Eder
Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
Klaus
K
Kopka
Department of Nuclear Medicine, University Hospital Heidelberg, Heidelberg, Germany.|Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, Heidelberg, Germany.
Uwe
U
Haberkorn
Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
Matthias
M
Roethke
Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
Heinz-Peter
HP
Schlemmer
Department of Nuclear Medicine, University Hospital Heidelberg, Heidelberg, Germany.
Ali
A
Afshar-Oromieh
D000368:Aged; D001859:Bone Neoplasms / Q000556:secondary*; D004492:Edetic Acid / Q000031:analogs & derivatives*; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009842:Oligopeptides; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D009842:Oligopeptides; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid
68Ga-PSMA; Bone metastases; Lymph node metastases; PET/CT; PET/MRI; PSMA