Diagnostic accuracy of [18F]-FDG-PET/CT for lymph node staging in bladder cancer prior to radical cystectomy.

PURPOSE: To evaluate the diagnostic accuracy of [18F]-FDG-PET/CT for lymph node (LN) staging prior to radical cystectomy (RC) in patients with bladder cancer, with a focus on the impact of neoadjuvant chemotherapy (NAC) on performance. METHODS: We retrospectively included all patients undergoing RC with pelvic lymph node dissection (PLND) for muscle-invasive or high-risk non-muscle invasive urothelial bladder cancer between January 2017 and April 2025 at a single tertiary centre. All patients underwent preoperative [18F]-FDG-PET/CT. Diagnostic performance was calculated using final histopathology as the reference standard. Subgroup analysis was performed based on NAC status. RESULTS: Among 103 patients (median age 71 years), 45 (43.7%) received NAC. The sensitivity, specificity, positive predictive value, and negative predictive value of [18F]-FDG-PET/CT for detecting LN metastases were 57.1%, 82.7%, 55.2%, and 83.8%, respectively. The area under the receiver operating characteristic curve (AUC) was 0.70 overall. In patients who received NAC, diagnostic performance improved markedly (AUC = 0.83 vs. 0.62 without NAC, p = 0.04), with increased sensitivity (80.0%) and NPV (93.8%). CONCLUSION: [18F]-FDG-PET/CT demonstrates moderate diagnostic accuracy for LN staging in bladder cancer, with good specificity but low sensitivity. Its diagnostic accuracy appears enhanced after NAC, indicating a potential role for [18F]-FDG-PET/CT in restaging after chemotherapy. However, more effective imaging tools are still needed to improve locoregional staging.