Imaging biomarkers of outcome after radiotherapy for pediatric ependymoma.

BACKGROUND AND PURPOSE: Ependymoma is the third most common brain tumor in children. Radiation therapy (RT) is systematically administered after maximum surgical resection, utilizing recent advances in radiation delivery. Imaging can make a significant contribution to improving treatment outcome. This prompted us to look for significant preoperative and postoperative imaging markers for survival. MATERIAL AND METHODS: We undertook a national retrospective review of 121 patients who had undergone resection followed by RT. Preoperative tumor volumes on T1 and FLAIR images were delineated, together with postoperative hyperintense volumes on FLAIR images. Overall survival (OS) and disease-free survival (DFS) analyses included clinical data and volumes extracted from images. RESULTS: After a median follow-up of 38.5 months, 80.2% of patients were alive, but 39.7% had experienced at least one event. Statistically significant differences between patients with and without postoperative FLAIR abnormalities were found for both DFS (71.9% vs. 40.3%; p = 0.006) and OS (93.7% vs. 72.4%; p = 0.023) in the univariate analyses, and for OS (p = 0.049) in the multivariate analyses. CONCLUSIONS: Postoperative FLAIR hyperintensities are a negative prognostic factor for intracranial ependymoma and may be a surrogate for residual disease. They could therefore prove helpful in patients' surgical and radiotherapeutic management.

Prognostic and predictive values of diffusion and perfusion MRI in paediatric intracranial ependymomas in a large national study.

OBJECTIVE: To assess the relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) derived, respectively, from perfusion and diffusion pre-operative MRI of intracranial ependymomas and their predictive and prognostic values. METHODS: Pre-operative MRI and clinical data for intracranial ependymomas diagnosed between January 2000 and December 2013 were retrospectively retrieved from a web-based national database. MRI data included diffusion (62 patients) and perfusion (20 patients) MRI. Patient age, histopathological diagnosis, tumour location, ADC, relative ADC (rADC) and rCBV were considered as potential factors in a survival analysis. Survival rates were estimated using the Kaplan-Meier method. Univariate analyses were performed using the log-rank test to compare groups. We also performed a multivariate analysis, applying the Cox proportional hazards model. RESULTS: ADC and rADC values within hypointense regions differed significantly between grades II and III (p = 0.01). The 75th percentile of ADC within hypointense regions and the 25th percentile of rCBV within non-enhancing lesions were prognostic of disease-free survival (p = 0.004, p = 0.05). A significant correlation was found between the 75th percentile of rCBV and the 25th percentile of rADC (p = 0.01) in enhancing regions of grade-III tumours. CONCLUSION: Pre-operative rADC and rCBV could be used as prognostic factors for clinical outcome and to predict histological grade in paediatric ependymomas. ADVANCES IN KNOWLEDGE: Prognostic value of diffusion and perfusion MRI in paediatric ependymoma was found and may play a role in the prognostic classification of patients in order to design more tailored treatment strategies.