(68)Ga-PSMA and (11)C-Choline comparison using a tri-modality PET/CT-MRI (3.0 T) system with a dedicated shuttle

BACKGROUND: The aim of this study was to prospectively compare the detection rate of (68)Ga-PSMA versus (11)C-Choline in men with prostate cancer with biochemical recurrence and to demonstrate the added value of a tri-modality PET/CT-MRI system. METHODS: We analysed 36 patients who underwent both (11)C-Choline PET/CT and (68)Ga-PSMA PET/CT scanning within a time window of 1-2 weeks. Additionally, for the (68)Ga-PSMA scan, we used a PET/CT-MRI (3.0 T) system with a dedicated shuttle, acquiring MRI images of the pelvis. RESULTS: Both scans were positive in 18 patients (50%) and negative in 8 patients (22%). Nine patients were positive with (68)Ga-PSMA alone (25%) and one with (11)C-Choline only (3%). The median detected lesion per patient was 2 for (68)Ga-PSMA (range 0-93) and 1 for (11)C-Choline (range 0-57). Tumour to background ratios in all concordant lesions (n = 96) were higher for (68)Ga-PSMA than for (11)C-Choline (110.3 ± 107.8 and 27.5 ± 17.1, mean ± S.D., for each tracer, respectively P = 0.0001). The number of detected lesions per patient was higher for (11)C-Choline in those with PSA ≥ 3.3 ng/mL, while the number of detected lesions was independent of PSA levels for (68)Ga-PSMA using the same PSA cut-off value. Metastatic pelvic lesions were found in 25 patients (69%) with (68)Ga-PSMA PET/CT, in 18 (50%) with (11)C-Choline PET/CT and in 21 (58%) with MRI (3.0 T). MRI was very useful in detecting recurrence in cases classified as indeterminate by means of PET/CT alone at prostate bed. CONCLUSIONS: In patients with prostate cancer with biochemical recurrence (68)Ga-PSMA detected more lesions per patient than (11)C-Choline, regardless of PSA levels. PET/CT-MRI (3.0 T) system is a feasible imaging modality that potentially adds useful relevant information with increased accuracy of diagnosis.