Fluorodeoxyglucose positron-emission tomography (FDG PET)/computed tomography (CT) in bladder cancer
In this month’s issue Mertens et al.  present a retrospective analysis of the clinical impact of fluorodeoxyglucose positron-emission tomography (FDG PET)/CT in 96 patients with muscle-invasive bladder cancer. Muscle invasion is present in ≈30% of patients presenting with bladder cancer and is associated with a higher incidence of nodal and metastatic disease than non-muscle-invasive tumours . Accurate staging in this patient group will influence management decisions to proceed to local therapies, to instigate neoadjuvant treatment before local therapy, or to offer palliative chemotherapy where there is imaging evidence and subsequent confirmation of metastatic disease .
While there have been a few previous studies investigating FDG PET or FDG PET/CT for staging bladder cancer [3-7], with reported sensitivities and specificities ranging from 60 to 81% and 67 to 94% respectively, to date there are few data describing the impact on clinical management. A recent FDG PET/CT study of 57 patients with bladder cancer  reported that management was changed in 68% of cases after PET suggesting that FDG PET/CT has a substantial impact on the management of these patients. However, most patients in that study underwent FDG PET/CT for a suspected recurrence (72%) and the remainder for initial staging (21%) or post-treatment monitoring (chemotherapy or radiotherapy; 7%); 44% of patients had metastatic disease.
In the study reported by Mertens et al. , clinical data obtained in 96 patients during the patients’ clinical pathway were reviewed retrospectively. FDG PET/CT staging with standard contrast-enhanced CT was discordant in 22% of cases (21 patients), where PET/CT predominantly upstaged patients, consistent with the previous reports [3, 4]. After PET/CT, the treatment recommendations changed in 13.5% (13 patients) due to disease upstaging. In seven of the 13 patients treatment recommendations altered from local to palliative, due to the presence of metastatic disease, and in the remaining six of the 13 patients, neoadjuvant treatment was recommended in addition to planned local therapy. In another four patients management changed as a consequence of detecting other incidental primary tumours with FDG PET/CT.
However, the final clinical impact of FDG PET/CT may be less. When actual treatment changes were recorded, in only eight of these 13 patients were the recommendations implemented, due to patient co-morbidity or patient wishes in the remainder, e.g. FDG PET/CT changed actual treatment in only 8% in this study (eight of 96 patients). Including the four patients in whom incidental other primary tumours were discovered, the management impact of FDG PET/CT was 12.5%.
There is no doubt that from current published data and supported by this study by Mertens et al.  that FDG PET/CT improves staging in bladder cancer due to its higher sensitivity for metastatic disease. However, the actual change in management is relatively low and more prospective data will be required to confirm its clinical and cost effectiveness in terms of outcome, both in a single and multicentre setting.
Vicky Goh*‡ and Gary Cook*†
*Division of Imaging Sciences and Biomedical Engineering, King’s College London, ‡Department of Radiology, and †Clinical PET Imaging Centre, Guy’s and St Thomas’ Hospitals NHS Foundation Trust, London, UK
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