Whole-Body Integrated [ 68 Ga]PSMA-11-PET/MR Imaging in Patients with Recurrent Prostate Cancer: Comparison with Whole-Body PET/CT as the Standard of Reference

Purpose The aim of this study was to evaluate the detection rate of [ 68 Ga]prostate-specific membrane antigen ([ 68 Ga]PSMA-11) positron emission tomography (PET)/magnetic resonance imaging (MRI) and to compare it with [ 68 Ga]PSMA-11 PET/X-ray computed tomography (CT) in patients with recurrent prostate cancer (PC) after radical prostatectomy. Procedures A total of 93 patients with biochemically recurrent prostate cancer underwent [ 68 Ga]PSMA-11 PET/CT and subsequently a whole-body integrated PET/MRI examination. Board certified nuclear medicine physicians and radiologists evaluated PET/CT and PET/MRI datasets regarding identification of tumor lesions ((i) lymph nodes, (ii) bone lesions, (iii) local recurrence, and (iv) parenchymal lesions) based on maximum [ 68 Ga]PSMA-11 uptake as well as morphological changes. Quality of PET images for both PET/CT and PET/MRI were rated using a 5-point scoring system by evaluating lesion homogeneity, contrast, contour, and delineation. Wilcoxon signed-rank tests were used to determine statistical differences. Results PC relapse was detected in 62/93 patients. PET/MRI detected 148 out of 150 lesions described in PET/CT. In addition, PET/MRI detected 11 lesions not detected in PET/CT (5 lymph nodes, 6 local recurrences). The exact McNemar statistical test (one-sided) showed significant difference between PET/CT and PET/MRI for diagnosis of local recurrence ( p value = 0.031). Diagnostic confidence for (iii) was higher in PET/MRI compared with PET/CT (PET/CT = 1.1; PET/MRI = 4.9). Diagnostic confidence for (i) (PET/CT = 4.9; PET/MRI = 4.6), (ii) (PET/CT = 4.9; PET/MRI = 4.6), and (iv) (PET/CT = 4.6; PET/MRI = 4.8) was equivalent between PET/MRI and PET/CT. Conclusions Integrated [ 68 Ga]PSMA-11 PET/MRI provides a similarly high diagnostic performance for localization of recurrent PC as PET/CT. For the detection of local recurrences [ 68 Ga]PSMA-11 PET/MRI is superior compared with [ 68 Ga]PSMA-11 PET/CT.