EPEN-13. PATTERN OF RELAPSE IN POSTERIOR FOSSA EPENDYMOMA GROUP A

PURPOSE/OBJECTIVE: Posterior fossa ependymoma group A (PF-EPN-A) is a poor prognostic ependymoma subgroup, predominantly seen in infants and young children. Among all ependymomas, most of the recurrences are seen in patients with the PF-EPN-A subgroup. Despite advances in neurosurgery and postoperative adjuvant therapy, management of these tumors remains challenging, and recurrence occurs in over 50% of cases. In this study, we aimed to evaluate the pattern of relapse in PF-EPN-A. MATERIALS AND METHODS: The clinical features, treatment strategies and relapse patterns of patients diagnosed and treated with PF-EPN-A at the Hospital for Sick Children, Toronto have been evaluated retrospectively. RESULTS: Seventy-five patients were diagnosed with PF-EPN-A at the Hospital for Sick Children, Toronto from 01 June 1996 to 01 June 2022. All patients were treated with surgery +/- focal radiation +/- chemotherapy after diagnosis. Out of 75 patients, 38 (50.6%) had recurrent disease. Twenty-three patients (60.5%) had a local relapse while 15 patients (40.5) experienced a distant relapse. Out of 23 patients who had a local relapse, only 8 patients (34%) developed a local relapse after a gross total resection (GTR). Other 15 patients developed a local relapse after either subtotal (STR) or near total resection (nTR). Out of 15 patients who experienced a distant relapse, 10 patients (66%) developed a distant relapse after GTR. Time to relapse was mean 32 months (11-132 months) after GTR and 24 months (1-98 months) after STR /nTR. CONCLUSIONS: The modern management approach (more aggressive resection and early conformal radiotherapy) changed the relapse pattern and the classical dogma that “nearly all relapses in ependymoma are local’’ in modern series. This study supported the importance of GTR in the management of PF-EPN-A and also demonstrated that PF-EPN-A tends to recur more on distant sites rather than locally when the initial surgical intervention is a GTR.