Prospective comparison of whole-body MRI and 68Ga-PSMA PET/CT for the detection of biochemical recurrence of prostate cancer after radical prostatectomy

PurposeTo assess whole-body magnetic resonance imaging (wb-MRI) for detection of biochemical recurrence in comparison to Ga-68-prostate-specific membrane antigen positron emission tomography/computed tomography (Ga-68-PSMA PET/CT) in prostate cancer (Pca) patients after radical prostatectomy.MethodsThis was a prospective trial including 28 consecutive patients (mean age 65.39.0years) with newly documented biochemical recurrence of Pca (mean prostate-specific antigen, PSA, 2.091.95ng/ml) following radical prostatectomy. All patients underwent both wb-MRI including a dedicated pelvic imaging protocol and PET/CT with 166 +/- 35MBq Ga-68-PSMA within a time window of 11 +/- 10days. PET/CT and MRI datasets were separately evaluated regarding Pca lesion count, type, localization and diagnostic confidence (three-point Likert scale, 1-3) by two nuclear medicine specialists and two radiologists, respectively. The reference standard was based on histopathological results, PSA levels following targeted salvage irradiation and follow-up imaging. Lesion-based and patient-based detection rates were compared using the chi-squared test. Differences in diagnostic confidence were assessed using the Welch test.Results A total of 56 Pca lesions were detected in 20 of the 28 patients. Ga-68-PSMA PET/CT detected 56 of 56 lesions (100%) in 20 patients (71.4%), while wb-MRI detected 13 lesions (23.2%) in 11 patients (39.3%). The higher detection rate with Ga-68-PSMA PET/CT was statistically significant on both a per-lesion basis (p<0.001) and a per-patient basis (p=0.0167). In 8 patients (28.6%) no relapse was detectable by either modality. All lesions detected by wb-MRI were also detected by Ga-68-PSMA PET/CT. Additionally, Ga-68-PSMA PET/CT provided superior diagnostic confidence in identifying Pca lesions (2.7 +/- 0.7 vs. 2.3 +/- 0.6, p=0.044).Conclusion Ga-68-PSMA PET/CT significantly out-performed wb-MRI in the detection of biochemical recurrence in Pca patients after radical prostatectomy.