CTNI-14. RADIOTHERAPY VERSUS TMZ FOR HIGH-RISK LOW-GRADE GLIOMA. FINAL RESULTS AFTER MEDIAN FOLLOW-UP OF 13 YEARS OF PHASE III EORTC/NCIC-CTG/TROG/MRC-CTU (EORTC 22033-26033) STUDY

Abstract BACKGROUND We previously reported on progression-free survival of our randomized phase 3 trial [Lancet Oncol. 2016;17:1521-1532]. Here we report results of long-term follow-up (FU) including overall survival (OS) and molecular subgroup analyses. METHODS 487 patients were randomized between 2005-2012 to either standard radiotherapy (RT, 50.4 Gy/ 28 fractions) or primary dose-dense temozolomide [TMZ] chemotherapy (75 mg/m² daily x 21/28 days, up to 12 cycles). Treatment at progression was at investigators discretion and commonly included cross-over to the alternative treatment modality. RESULTS At a median follow-up of 13 years, 68% of patients had died. Median age at inclusion was 45 years (range 18-75), 96% had a performance status of 0-1. There was no significant difference in PFS nor OS: PFS was 3.6 years (95% CI: 3.0-4.1) and 3.1 years (95% CI: 2.7-3.6), HR 1.12 (95% CI: 0.92-1.36); OS 6.6 years (95% CI: 5.8-7.5) and 8.0 years (95% CI: 6.9-9.1), HR 0.87 (95% CI: 0.69-1.09), for RT or TMZ, respectively. Subgroup analyses were performed for patients when available tissue allowed for molecular analyses (n=351/487,73%). In astrocytoma, IDHmt/1p/19q non-codeleted (n = 178), median OS with RT was 6.6 years (95% CI: 5.3-7.6) and with TMZ was 6.7 years (95% CI: 5.7-8.0); HR 0.98 (95% CI: 0.67-1.44). For oligodendroglioma, IDHmt/codeleted (n = 109) median OS with RT was 12.9 years (95% CI: 9.4 - NE) and with TMZ 14.9 years (95% CI: 10.1 - NE); HR 1.01 (95% CI: 0.56-1.81). For a heterogenous group of IDHwt tumors (n = 64), median OS with RT was 2.5 years (95% CI: 1.8-3.3) and with TMZ 4.7 years (95% CI: 2.2-7.2); HR 0.37 (95% CI: 0.18-0.77). CONCLUSIONS Primary treatment with RT or TMZ provided comparable PFS and OS. Choice of primary treatment can be tailored to individual tumor characteristics and patient preference.