Can Whole-body MRI Replace CT in Management of Metastatic Testicular Cancer? A Prospective, Non-inferiority Study.

Purpose Concerns of imaging-related radiation in young patients with high survival rates have increased the use of magnetic resonance imaging (MRI) in testicular cancer (TC) stage I. However, computed tomography (CT) is still preferred for metastatic TC. The purpose of this study was to compare whole-body MRI incl. diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) with contrast-enhanced, thoracoabdominal CT in metastatic TC.Methods A prospective, non-inferiority study of 84 consecutive patients (median age 33 years) with newly diagnosed metastatic TC (February 2018 - January 2021). Exclusion criteria were age <18 years, claustrophobia and MRI contraindications. Patients had both MRI and CT before and after treatment. Anonymised images were reviewed by experienced radiologists.Lesion malignancy was evaluated on a Likert scale (1 benign – 4 malignant). Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated on patient and lesion level. For non-inferiority testing, the difference in sensitivity between CT and MRI was calculated. The level of significance was set at 5%. ROC curves and interobserver agreement were calculated.Results On patient level, MRI had 98% sensitivity and 75% specificity compared to CT. On lesion level within each modality, MRI had 99% sensitivity and 78% specificity, whereas CT had 98% sensitivity and 88% specificity. MRI sensitivity was non-inferior to CT (difference 0.57% (95% CI -1.4-2.5%)). The interobserver agreement was substantial between CT and MRI. Conclusion MRI with DWIBS was non-inferior to contrast-enhanced CT in detecting metastatic TC disease. Trial registration www.clinicaltrials.gov NCT03436901, finished July 1st 2021.