Siop Ependymoma I: Final Results, Long Term Follow-Up And Molecular Analysis Of The Trial Cohort: A Biomeca Consortium Study

Background SIOP Ependymoma I was a non-randomised trial assessing event free and overall survival (EFS/OS) of non-metastatic intracranial ependymoma in children aged 3-21 years treated with a staged management strategy. A further aim was to assess the response rate (RR) of subtotally resected (STR) ependymoma to vincristine, etoposide, and cyclophosphamide (VEC). We report final results with 12-year follow-up and post hoc analyses of recently described biomarkers. Methods Seventy-four participants were eligible. Children with gross total resection (GTR) received radiotherapy, whilst those with STR received VEC before radiotherapy. DNA methylation, 1q, hTERT, ReLA, Tenascin-C, H3K27me3, and pAKT status were evaluated. Results Five- and ten-year EFS was 49.5% and 46.7%, OS was 69.3% and 60.5%. GTR was achieved in 33/74 (44.6%) and associated with improved EFS (P = .003, HR = 2.6, 95% confidence interval (CI) 1.4-5.1). Grade 3 tumours were associated with worse OS (P = .005, HR = 2.8, 95%CI 1.3-5.8). 1q gain and hTERT expression were associated with poorer EFS (P = .003, HR = 2.70, 95%CI 1.49-6.10 and P = .014, HR = 5.8, 95%CI 1.2-28) and H3K27me3 loss with worse OS (P = .003, HR = 4.6, 95%CI 1.5-13.2). Methylation profiles showed expected patterns. 12 participants with STR did not receive chemotherapy; a protocol violation. However, best chemotherapy RR was 65.5% (19/29, 95%CI 45.7-82.1), exceeding the prespecified 45%. Conclusions Participants with totally resected ependymoma had the best outcomes. RR of STR to VEC exceeded the pre-specified efficacy criterion. However, cases of inaccurate stratification highlighted the need for rapid central review. 1q gain, H3K27me3 loss, and hTERT expression were all associated with poorer survival outcomes.