Pilot Study of [18F] Fluorodeoxyglucose Positron Emission Tomography (FDG-PET)-Magnetic Resonance Imaging (MRI) for Staging of Muscle-Invasive Bladder Cancer (MIBC)

Abstract Introduction/Background Computed tomography (CT) has limited diagnostic accuracy for staging of muscle-invasive bladder cancer (MIBC). [18F] Fluorodeoxyglucose positron emission tomography (FDG-PET)/magnetic resonance imaging (MRI) is a novel imaging modality incorporating functional imaging with improved soft tissue characterization. This pilot study evaluated the use of preoperative FDG-PET/MRI for staging of MIBC. Patients and Methods 21 MIBC patients with planned radical cystectomy were enrolled. Two teams of radiologists reviewed FDG-PET/MRI scans to determine: 1) presence of primary bladder tumor; and 2) lymph node involvement and distant metastases. FDG-PET/MRI was compared to cystectomy pathology and CT. Results 18 patients were included in the final analysis, most of whom received neoadjuvant chemotherapy (72.2%). Final pathology revealed 10 patients (56%) with muscle invasion and only 3 patients (17%) with lymph node involvement. Clustered analysis of FDG-PET/MRI radiology team reads revealed a sensitivity 0.80 and specificity 0.56 for detection of the primary tumor with a sensitivity 0 and specificity 1.00 for detection of lymph node involvement when compared to cystectomy pathology. CT imaging demonstrated similar rates in evaluation of the primary tumor (sensitivity 0.91, specificity 0.43) and lymph node involvement (sensitivity 0, specificity 0.93) when compared to pathology. Conclusions This pilot single-institution experience of FDG-PET/MRI for preoperative staging of MIBC performed similar to CT for the detection of the primary tumor, however, the determination of lymph node status was limited by few patients with true pathological lymph node involvement. Further studies are needed to evaluate the potential role for FDG-PET/MRI in the staging of MIBC.