EPEN-01. Response assessment in pediatric intracranial ependymoma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group

Abstract INTRODUCTION: Ependymomas remain a major cause of cancer-related death in childhood and adolescence, with recurrence occurring in up to 50% of patients. Despite exciting molecular advances in understanding ependymoma tumorigenesis and recurrence, MRI remains the mainstay for assessing objective response to therapy and duration of disease stability. Standardized response assessment criteria for clinical trials studying pediatric intracranial ependymoma are critically needed in order to accurately compare results between studies. METHODS: To generate these standardized response criteria in pediatric intracranial ependymoma, a multidisciplinary team of pediatric neuro-oncologists, neuroradiologists, neurosurgeons, radiation oncologists, and molecular biologists formed the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group. The expert members reviewed relevant published literature, assessed current clinical practices, and engaged in iterative discussions to provide consensus recommendations for objective response assessment in pediatric intracranial ependymoma for use in prospective clinical trials. RECOMMENDATIONS AND CONCLUSIONS: The primary sequences for detecting and measuring disease and assessing radiologic response to therapy should be the contrast-enhanced T1-weighted sequence or T2-weighted sequence (T2 or T2-FLAIR) depending on which sequence the tumor is best visualized. When metastatic disease is present, only the three largest lesions will be followed in addition to any residual disease at the primary tumor focus. Importantly, the RAPNO working group notes that radiologic response to therapy is of limited value in clinical trials of patients with ependymoma, since most patients enroll on clinical trials with either no evidence of disease or only minimal disease. In recurrent or progressive disease that cannot be resected, true radiologic disease response to therapy is less clinically meaningful as a study endpoint than event-free and/or overall survival (representing prolonged stable disease) but may provide a signal of efficacy worthy of future exploration in patients with complete to near complete resections.