Urothelial CancerDetection of Lymph Node Metastasis in Patients with Bladder Cancer using Maximum Standardised Uptake Value and 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography: Results from a High-volume Centre Including Long-term Follow-up
Introduction
Radical cystectomy (RC) with lymph node (LN) dissection is the preferred treatment of nonmetastatic muscle-invasive or high-risk nonmuscle-invasive bladder cancer [1]. However, despite negative preoperative metastatic work-up, approximately 20% of patients are upstaged postoperatively due to occult LN involvement when comparing 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) with CT alone [2], [3]. It is difficult to identify low-risk cT2N0 RC, and approximately 30% of patients with cT2N0 disease may have nonorgan-confined tumour or nodal involvement [4].
Choice of treatment is limited by the inability to predict metastases and lymphatic involvement using current standard imaging modalities like CT. Staging with conventional CT has only moderate accuracy in identifying true LN-positive disease based on shape and size and does not provide information on the metabolism of the disease. PET provides information on the potential malignancy of a LN through glucose metabolism by 18F-FDG uptake. 18F-FDG PET/CT has been found to be superior compared with conventional imaging regarding the identification of nodal and metastatic involvement in bladder cancer [5], [6], [7]. Correctly identifying true positive LNs caused by tumour infiltration remains difficult due to false-positive LNs where 18F-FDG uptake is caused by inflammation [8].
Quantification of the 18F-FDG PET/CT signal can be described as the signal expressed as the standardised uptake value (SUV) compared with background ratios in a region of interest. Combining the anatomical stronghold of CT (eg, size and shape of LNs) with a quantitative measurement of 18F-FDG PET uptake utilising maximum SUV (SUVmax) could be a way of distinguishing causes for increased glycolysis and thereby gaining better preoperative staging.
The objective of this study was to assess the utility of SUVmax in 18F-FDG PET/CT in detecting regional nodal metastases in patients considered for RC.
Section snippets
Patient material
Between September 2011 and April 2014, a total of 328 patients at a single large tertiary urological cancer centre were considered for RC due to muscle-invasive bladder cancer or high-risk nonmuscle-invasive disease.
All patients underwent preoperative 18F-FDG PET/CT at the time of diagnosis. A total of 197 patients were excluded from the study based on the following exclusion criteria (Fig. 1): (1) prior neoadjuvant or downstaging chemotherapy administered between the time of PET/CT and RC (n =
Results
The median age was 72.5 yr and sex distribution was 79% men (n = 104) and 21% women (n = 27). The median time between PET/CT and RC was 24 d (median range, 5–68).
The median LN yield per patient was 19 LN (6–41). A total number of 2278 LNs were archived from eLND during RC (n = 90) and RALRC (n = 29), and fine needle aspiration cytology contributed with 13 LNs from 12 patients. In total, 2292 LNs were identified on histology (Table 1).
Eight-five LN metastases from bladder cancer were found in 34
Discussion
The overall trend in PET/CT studies seems to be a high specificity and an acceptable accuracy [6], [7], [12], [13]. Higher specificity can be found at higher values of SUVmax (eg, SUVmax >4, 91%) showing the specificity is susceptible to deviance according to signal interpretation used in evaluation.
Scanners, settings, and patients are susceptible for deviation and exact SUVmax values are therefore hard to reproduce. Standardisation of PET/CT scanning is imperative in the setup and evaluation
Conclusions
Our data support the existing literature suggesting that PET/CT and SUVmax interpretation is an appropriate tool in the evaluation of LN and can be used prior to surgery to make a safe identification of positive LNs. This has important clinical implications when selecting patients for a more personalised treatment prior to RC, while the indication for Neoadjuvant chemotherapy in patients without PET-positive LNs is debatable.
Author contributions: Stefan Vind-Kezunovic had full access to all the
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