A comparison between computerised tomography and magnetic resonance imaging in the primary staging of bladder cancer as compared to final histology

Abstract

Introduction: Accurate and effective imaging to determine the stage of the primary tumour is crucial in deciding whether patients should be treated conservatively, or with surgical or radiochemotherapeutic treatment. There are still concerns about the staging accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) scanners. Methods: We conducted a retrospective analysis of 254 single-surgeon radical cystectomies on a population destined for potentially curative surgery (without evidence of metastatic disease) over 14 years. We compared the staging accuracy of 245 CT scans against 62 conventional T2-weighted MRI scans and compared them to the absolute gold standard, histological analysis using the TNM staging system. Results: Overall, when comparing all the scanner results from 1999 to 2016, the following was observed: • MRI initially appears to be better than CT in staging the primary tumour as either localised or locally advanced disease; and • CT is significantly better than MRI for nodal staging. However, when comparing the more recent results using 53 patients who had both CT and MRI prior to operation, from 2005 to 2016, we find CT improves to match MRI in both primary tumour staging and nodal staging with ‘fair’ kappa scores ( p = 0.84). Conclusions: We confirm that MRI is better at staging extravesical disease and CT better at staging localised disease. Regarding primary tumour accuracy, the volume of the tumour has an influence on its correct staging. Regarding nodal accuracy, the presence of extracapsular extension had no influence. Knowing these limitations of the two modalities should enable better counselling of patients, regardless of their subsequent treatment regimen.