The contribution of multiparametric pelvic & whole body MR to interpretation of 18F-fluoromethylcholine or 68Ga-HBED-CC PSMA-11 PET/CT in patients with biochemical failure following radical prostatectomy

Purpose: To assess whether the addition of data from multiparametric pelvic (mpMR) and whole body MR (wbMR) to the interpretation of 18F-fluoromethylcholine (FCH) or 68Ga-HBED-CC PSMA-11 (PSMA) PET/CT (=PET) improves the detection of local tumor recurrence, or nodal and distant metastases in patients following radical prostatectomy with biochemical failure. Methods: The current analysis was performed as part of a prospective, multicenter trial on FCH / PSMA PET, mpMR and wbMR. Eligible men had elevated PSA (>0.2 ng/ml) and high-risk features (Gleason score >7, PSA doubling time < 10 months, or PSA>1.0 ng/ml) with negative/ equivocal conventional imaging. PET was interpreted with mp&wbMR in consensus by 2 radiologists and compared to prospective interpretation of PET or MR alone. Performance measures of each modality (PET, MR & PET/mp-wbMR) were compared for each radiotracer, for each individual patient (for FCH, or PSMA for patients who had PSMA PET), and to a composite reference standard. Results: There were 86 patients with PET (FCH [n=76] and/or PSMA [n=26]) who had mp&wbMR. Local tumor recurrence was detected in 20/76 (26.3%) on FCH PET/mpMR vs 11/76 (14.5%) on FCH PET (p= 0.039) and 11/26 (42.3%) on PSMA PET/mpMR vs 6/26 (23.1%) on PSMA PET (p=0.074). Per patient, PET/mpMR was more often positive for local tumor recurrence than PET (p=0.039) or mpMR (p=0.019). There were 20/86 (23.3%) patients with regional nodal metastases on both PET/wbMR, and PET (p=1.0) but only 12/86 (14%) on wbMR (p=0.061). Similarly, there were more nonregional metastases detected on PET/wbMR than on PET (p=0.683) and wbMR (p=0.074), but these differences did not reach significance. Compared to the composite reference standard for the detection of disease beyond the prostatic fossa PET/wbMR, PET and wbMR had sensitivity of 50%, 50%, 8.3%, respectively & specificity of 97.1%, 97.1%, 94.1%, respectively. Conclusion: Interpretation of PET with mpMR resulted in a higher detection rate for local tumor recurrence in the prostate bed in men with biochemical failure following radical prostatectomy. However, the addition of wbMR to FCH/PSMA PET did not improve detection of regional or distant metastases