Purpose: Contrast-enhanced MRI (MRI + C) is considered as mandatory for brain tumors follow-up, but gadolinium brain depositions in relation with repeated injections have been reported. The aim of our work was to evaluate the diagnostic performance of an unenhanced MRI examination for the follow-up of optic pathway gliomas (OPG) in children.
Methods: Seventeen patients (with/without NF1) were selected from 2001 to 2017, with at least 5 MRI + C brain follow-up examinations. Privacy and data protection rights were addressed by the data protection officer (DPO) and the study was in accordance with the local ethical rules. Twenty-five cases of tumor progression and 25 cases of tumor stability mentioned in the conclusion of radiological reports (defined as gold standard) were isolated. Those exams were anonymized and independently reviewed by two radiologists, who analyzed both quantitative (such as tumor volume variation) and qualitative criteria (such as ventricular dilatation) on unenhanced images. Sensitivity, specificity, positive/negative predictive values (PPV, NPV), and inter/intra-observer agreement were calculated.
Results: The mean age of patients was 5.4 ± 3.4 years and mean follow-up length 6.7 years. The mean number of MRI + C was 13.5 (SD 7.2). The sensitivity of unenhanced MRI for tumor follow-up was 84-88% (95% CI 63.9-97.5). The specificity was 91.3-100% (95% CI 72-100). The PPV was 91.7% for reader 1 and 100% for reader 2. The NVP was 87.5% for reader 1 and 85.2% for reader 2. There was an excellent inter-observer agreement regarding tumor progression: kappa coefficient of 0.87 (p < 0.001). Inter/intra-variability for percentage of tumor volume variation between two exams were good (correlation coefficients of 0.97 and 0.94).
Conclusion: Tumor volume variation is in most cases sufficient to assess OPG progression. Systematic MRI + C could be questionable.
Keywords: Children; MRI; Neurofibromatosis type 1; Optic pathway glioma.