Standard imaging as CT and MRI have been failed in detecting lymph node metastasis (LNM) in muscle invasive bladder cancer (MIBC). Recently [18F]-FDG PET/CT has been reported to be more sensitive than CT and MR in staging MIBC, but no data has been reported about its role in non-muscle invasive bladder cancer (NMIBC). We investigated the potential clinical performance of [18F]-FDG PET/CT in staging and decision-making (bladder sparing) in patients with high-risk (HR-NMIBC).
This is prospective, exploratory study, in patients with MIBC and HR or very HR (VHR) NMIBC, according to EAU guideline, who were candidate to radical cystectomy at our tertiary University Hospital. Patients were enrolled if they had primary T2 or higher, T1 HG/G3 with or without CIS or BCG failure NMIBC. We compare pre-operative diagnostic performance by [18F]-FDG PET/CT with administration of furosemide (20 mg / 2 ml) 30 minutes after the injection of 394 MBq of 18F-FDG, with pathological data in patients who underwent radical cystectomy (RC) and concomitant pelvic lymph node dissection (LND). We defined the capacity of avoiding over-/under-treatment by local staging and LNM detection in patients with HR- VHR-NMIBC by sensitivity, specificity, NPV and PPV.
From September 2020 to July 2021, 47 patients were enrolled. Overall [18F]FDG-PET/CT correctly identified 13/19 true positive and 23/28 true negative LNM (sensitivity 68.4%, specificity 82.1%, PPV 72.2%, NPV 79.3%; AUC 75.3% [95% CI 62.3%-88.2%]). In the 34 patients with definitive MIBC, [18F]FDG-PET/CT correctly identified 10/16 true positive and 16/18 true negative lymph nodes (sensitivity 62.5%, specificity 88.9%, PPV 83.3%, NPV 72.7%; AUC=75.7% [95% CI 61.3%-98.6%]), In 13 NMIBC patients the sensitivity was 100%, specificity 70%, with a PPV of 50% and a NPV of 100%. The AUC was higher in NMIBC than MIBC: 85% [95% CI 70%-100%]. Figure1 presents a patient with NMIBC and negative lymph nodes (a), and a patient with a VHR-NMIBC with multiple positive pelvic lymph nodes (b; arrows). 
These preliminary findings showed that [18F]FDG-PET/CT, with diuretic administration and delayed acquisition, may detect LNM in NMIBC and it could be an accurate tool for decision making (bladder sparing or not) in HR- or VHR-NMIBC. Larger and multi-institutional series remain mandatory to confirm our data.