Pelvic Lymph Node Staging by Combined 18F-FDG-PET/CT Imaging in Bladder Cancer Prior to Radical Cystectomy
Lymph node (LN) metastases are important predictors for poor oncologic outcome. Therefore, accurate LN staging in bladder cancer before radical cystectomy is essential. Most studies used a 10 mm cutoff in detecting LN spread. We identified the “best” cutoff for detecting pelvic LN metastases at 8 mm. Using this cutoff, additional 18F-fluorodeoxyglucose positron emission tomography is not recommended in preoperative staging.Background:
Accurate lymph node (LN) staging in bladder cancer before radical cystectomy is essential as LN metastases have an independent prognostic value. Most studies used a cutoff of > 10 mm in detecting pelvic LN spread. The aim of this study was to evaluate the diagnostic accuracy of contrast-enhanced computed tomography (CT) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) alone, or combined for preoperative pelvic LN staging.Patients and Methods:
We retrospectively analyzed the data of 70 bladder cancer patients that were staged with 18F-FDG-PET/CT before radical cystectomy between 2012 and 2015. 18F-FDG-PET images were analyzed visually and semi-quantitatively by calculating the maximum standardized uptake value. CT scans were reviewed using different cutoffs of pelvic LNs, with the best cutoff at 8 mm (area under the curve = 0.684).Results:
Metastatic LNs were confirmed in 53 (2.8%) of 1906 resected LNs in 11 (15.7%) patients. Sensitivity, specificity, and accuracy were 54.5%, 89.8%, and 84.3% for 18F-FDG-PET alone; 45.5%, 91.5%, and 84.3% for CT (LNs > 8 mm) alone; and 27.3%, 96.6%, and 85.7% for CT (LNs > 10 mm) alone, respectively. Combined 18F-FDG-PET/CT resulted in a nonsignificant increase of diagnostic accuracy using a cutoff > 8 mm for LN evaluation (63.6%, 86.4%, and 82.9%, respectively). A significant improvement of sensitivity to 63.6% was achieved only when LNs > 10 mm were considered suspicious (P = .046), but this reduced specificity to 88.1% (P = .025).Conclusions:
Combined 18F-FDG-PET/CT does not seem to be justified in preoperative staging if the threshold of pelvic LNs is set > 8 mm.