Pelvic Lymph Node Staging by Combined 18F-FDG-PET/CT Imaging in Bladder Cancer Prior to Radical Cystectomy

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Abstract

Micro-Abstract

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.

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