Original StudyPelvic Lymph Node Staging by Combined 18F-FDG-PET/CT Imaging in Bladder Cancer Prior to Radical Cystectomy
Introduction
Radical cystectomy (RC) with extended pelvic lymph node (LN) dissection is recommended as the standard therapy in patients with localized muscle-invasive bladder cancer (MIBC), Bacillus Calmette-Guerin-refractory high-risk non–muscle-invasive bladder cancer (NMIBC), or NMIBC at highest risk of tumor progression.1 However, despite negative local staging, 25% to 30% of patients present with occult pelvic LN metastases at the time of surgery.2, 3, 4 This fact is crucial, as positive LN status is one of the most important predictors for poor oncologic outcome.5, 6 Therefore, accurate preoperative staging is essential, changing treatment strategy in those patients with metastatic spread.7 However, the diagnostic accuracy of standard imaging methods remains low, with controversial results. One explanation can be seen in the discrepancy between the defined threshold of pelvic LN size regarded as pathologically enlarged. Whereas sensitivity ranged only between 9.1% and 29.4% for computed tomography (CT) (LNs > 10 mm) in detecting pelvic LN metastases,8, 9 an increase of sensitivity up to 46% could be achieved by cutoff values > 8 mm.10 Another point is the inability to identify metastases in normal-sized pelvic LNs. Between 29.4% and 68% of false-negative pelvic LNs on standard imaging were micrometastasis < 5 mm on histopathology.11, 12 A recently published study also confirmed that LNs between 6 and 10 mm on preoperative CT were associated with a significantly worse prognosis and higher risk of death after RC.13
Over the last few years, positron emission tomography (PET) is thought to have a diagnostic and prognostic impact in urologic oncology.14, 15 As 18F-fluorodeoxyglucose (18F-FDG) is not a useful tracer for primary bladder cancer detection, owing to its high renal excretion, trials investigated its role in pelvic LN staging, but with very disappointing results.10, 14, 15 Therefore, 18F-FDG-PET is still not recommended in routine LN staging of bladder cancer by the European Association of Urology guidelines.1
The aim of this study was to evaluate if dual imaging by 18F-FDG-PET/CT would increase the diagnostic accuracy in identifying pelvic LN spread in bladder cancer before RC compared with CT alone, using different cutoffs of pelvic LN size.
Section snippets
Materials and Methods
This study was performed according to the principles of the Declaration of Helsinki and its subsequent amendments.16 After approval by the local ethics committee (study number AN2015-0085; 348/4.10), medical records of patients with localized MIBC or recurrent, high-risk NMIBC undergoing preoperative staging by 18F-FDG-PET/CT prior to RC between September 2012 and August 2015 were reviewed retrospectively. The mean time interval between imaging and RC was 21.4 days (range, 14-34 days). Patients
Results
Descriptive and histopathologic characteristics of patients are summarized in Table 1. A total of 70 patients (53 male, 17 female) with a mean age of 69.3 years (range, 38-82 years) fulfilled the inclusion criteria. Orthotopic studer ileal neobladder, ileal conduit, and continent cutaneous catheterizable navel pouch was performed in 30 patients (42.9%), 39 patients (55.7%) and 1 patient (1.4%), respectively. Age (mean ± SD) was significantly lower in patients with orthotopic urinary diversion
Discussion
The current standard imaging methods have similar diagnostic accuracy in detecting pelvic LN metastases ranging from 54% to 97% for CT, and 73% to 98% for magnetic resonance imaging (MRI).18 A more accurate LN staging before cystectomy would be helpful in identifying those patients with metastatic disease, changing treatment plans in up to 27% (18F-FDG-PET/CT) with the possibility to reduce the number of RCs in patients where disease has spread beyond cure.19 Another advantage would be to
Conclusions
We may recommend an additional 18F-FDG-PET imaging in the routine preoperative LN staging in bladder cancer patients before cystectomy, if the threshold of positive pelvic LNs at CT evaluation is set on 10 mm. However, using the best validated cutoff of 8 mm, 18F-FDG-PET in addition to CT does not significantly improve the diagnostic accuracy in detecting pelvic LN metastases and can thus be avoided.
Disclosure
The authors have stated that they have no conflicts of interest.
Acknowledgment
The authors thank Hannes Steiner and Lorraine Burdett for their support and helpful contribution to this work.
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2021, Hematology/Oncology Clinics of North AmericaCitation Excerpt :PET with 18F-fluoro-d-glucose is not currently recommended for local staging of BCa because of the excretion of radiotracer into the bladder. However, evidence supports its potential role in other settings: PET/CT could improve detection of involved nodes that are still not considered abnormal by size criteria.27 Also, it could potentially be used to assess any other sites of metastasis when surgical resection is being considered for oligometastatic disease.28
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2021, Urologic Oncology: Seminars and Original InvestigationsCitation Excerpt :evaluated various node size cut-offs, which ranged from 6.8 mm to 10 mm. Their study commented on an increase from 8 mm to 10 mm as a cut-off that did not increase specificity, but decreased sensitivity twofold [28]. In a study by Schmid et al., lymph nodes between 5 mm and 10 mm, usually classified as nonpathologic, were associated with a significantly worse prognosis.