2007 Background: Outcome of low-grade glioma (LGG) is highly variable. We investigated whether primary chemotherapy in comparison to standard radiotherapy (RT) prolongs progression-free (PFS) and overall survival (OS), and whether prognostic molecular factors could be defined. Methods: Progressive, symptomatic or high-risk patients with a LGG requiring treatment other than surgery were randomized (after stratification for 1p-status) to either conformal RT (50.4 Gy/28 fractions) or dose-dense temozolomide [TMZ] (75 mg/m² daily x 21 days, q28 days, max. 12 cycles). Primary endpoint was PFS, secondary analyses included OS and impact of 1p status. Results: 477 patients were randomized (2005-2012, median FU 45.5 months). Analysis was performed after 246 progression events. Hematological toxicity ≥ grade 3 was observed in 9.4% of TMZ patients. PFS was not significantly different, median OS not reached. 1p deletion was a positive prognostic factor irrespective of treatment (p-value stratified by treatment (PFS: ...