18(F)choline PET/CT and Prostate MRI for Staging of Biochemical Relapse After Radiation Therapy of Prostate Cancer

Abstract

To evaluate 18:F-CholinePET/CT (PET) and MRI for anatomical localization of relapse after RT. Patients with Biochemical relapse (BR)(PSA ≥ nadir + 2 ng/mL) underwent combined PET and pelvic/prostatic MRI. MRI included T2-weighted, diffusion-weighted and dynamic-enhanced sequences. Population: 31 pts with a BR after brachytherapy (BT, n = 9) or external beam RT (EBRT; n = 22). Mean age and PSA value at relapse were 72 yrs (± 2) and 6.6 ng/mL (± 0.6), respectively. Initial Gleason score (GS): GS 6: 9 pts; GS 7: 16 pts; GS 8-10: 6 pts. Initial prognostic group; Favorable: 8; Intermediate: 13; Unfavorable: 10. Localization of relapse was defined in 27/31 cases (87%). In 4 pts, MRI and PET did not identify the relapse. MRI found a local relapse in 18 (58%), confirmed by TEP in 13 cases with a good agreement of the images inside the prostate for 11 pts. Distant relapses, nodal or metastatic, were found in 14 cases (45%) by TEP. Unusual nodal localizations (presacral or mediastinal nodes) were found in 4 cases. Globally, agreement between TEP and MRI was observed in 22 cases (71%). Discrepancies were due in 7 cases to a local relapse not seen on TEP, one false negative of MRI and one false positive of TEP. Eighteen(F) Choline PET/CT was less sensitive than MRI to detect local relapses, but allowed the diagnosis of distant metastasis, then could spared the patients of an unuseful salvage local treatment. Combined modalities could detect the relapse in 87% of the cases and defined accurately the population suitable for a second local treatment.