Clinical value of 18FDG PET/MRI in muscle-invasive, locally advanced, and metastatic bladder cancer.

Civelek, Ali Cahid; Niglio, Scot A; Malayeri, Ashkan A; Lin, Jeffrey; Gurram, Sandeep; Chalfin, Heather J; Turkbey, Baris; Valera, Vladimir; Steinberg, Seth M; Apolo, Andrea B

OBJECTIVE Metastatic bladder cancer is an aggressive disease that can often be difficult to diagnose and stage with conventional cross-sectional imaging. The primary objective of this study was to determine the clinical value of fluorine-18 2-fluoro-2-deoxy-D-glucose (18F-FDG) PET/MRI for surveillance and restaging of patients with muscle-invasive, locally advanced, and metastatic bladder cancer compared to conventional imaging methods. MATERIALS AND METHODS This retrospective study enrolled patients with muscle-invasive, locally advanced and metastatic bladder cancer in a single institute evaluated with 18F-FDG PET/MRI. All patients also underwent conventional imaging with CT. Additional imaging may also have included 18F-FDG PET/CT (18F-FDG PET), or sodium fluoride (NaF) PET/CT in some patients. Images were reviewed by a diagnostic radiologist/nuclear medicine physician. Number of lesions and sites of disease were captured and compared between 18F-FDG PET/MRI and conventional imaging. Lesions were confirmed by sequential imaging or lesion biopsy. All patients were followed for survival. RESULTS Fifteen patients (4 for surveillance; 11 for restaging) underwent 34 18F-FDG PET/MRI scans. Each patient received a corresponding conventional CT around the time of the 18F-FDG PET/MRI (median 6 days). The 15 patients (11 male; 4 female) had a median age of 61.5 years (range 37-73) and histologies of urothelial carcinoma (n = 13) and small-cell carcinoma of the bladder (n = 2) diagnosed as stage 4 (n = 13), stage 3 (n = 1), or stage 2 (n = 1). 18F-FDG PET/MRI detected 82 metastatic malignant lesions involving lymph nodes (n = 22), liver (n = 10), lung (n = 34), soft tissue (n = 12), adrenal glands (n = 1), prostate (n = 1), and bone (n = 2) with a resultant advantage of 36% for lesion visibility in comparison with CT. Serial imaging or biopsy confirmed these lesions as malignant. CONCLUSION 18F-FDG PET/MRI can detect metastatic lesions which cannot be identified on conventional CT, and this can allow for better treatment planning and improved disease monitoring during therapy.