Long-term outcomes after adjuvant radiotherapy in adult spinal ependymomas: a multicenter study by the trod Neuro-Oncology research group (07 - 005).

PURPOSE: The optimal adjuvant treatment strategy for spinal ependymomas (SEs) is controversial, especially in patients with adverse risk factors. The efficacy of adjuvant radiotherapy (RT) and its prognostic factors remain understudied. METHODS: This retrospective, multicenter study analyzed 45 adult patients (≥ 18 years) with histologically proven SE (WHO Grade 2 and 3) treated with RT between 1998 and 2024. Patients with Grade 1 tumors or surgery-to-RT intervals exceeding 6 months were excluded. Clinical outcomes were estimated using the Kaplan-Meier method, and prognostic factors were identified using multivariate Cox regression analysis. RESULTS: In the Grade 2 cohort (n = 37; median follow-up: 7.9 years), gross total resection (GTR) was achieved in 43.2% of patients. Extent of resection served as the primary determinant of disease control: zero local failures occurred in the GTR group (100% 10-year local control (LC) and disease-free survival (DFS), whereas 41.2% of non-GTR patients experienced local failure (5- and 10-year DFS: 63.9% and 54.7%, respectively; p = 0.006). Despite superior local control with GTR, overall survival remained statistically similar between resection groups (10-year OS: 88.9% for GTR vs. 74.3% for non-GTR; p = 0.70). In non-GTR patients without initial dissemination, a surgery-to-RT interval exceeding 1.5 months was identified as the sole independent predictor of early recurrence (HR: 13.3 and 15.9 for DFS and PFS, p = 0.04 for both). Additionally, younger age and baseline spinal dissemination were independent adverse prognostic factors for progression and mortality. For Grade 3 tumors, the 5-year LC, progression-free survival, and OS rates were 56.3%, 41.7%, and 75.0%, respectively, with a 62.5% progression rate. Although GTR achieved complete LC in Grade 3 tumors, distant metastasis remained a primary pattern of failure, occurring in 60% of progressive cases. For patients with initial spinal dissemination, the progression rate was 60% with a median OS of 15.2 months. CONCLUSION: While GTR remains the gold standard for long-term prognosis, adjuvant RT provides effective LC in Grade 2 SE patients with residual disease. Early adjuvant RT (within 1.5 months post-surgery) is a critical management strategy for non-GTR cases. Grade 3 histology and initial spinal dissemination remain significant indicators of poor long-term survival.