The evolutionary processes that drive malignant progression of IDH-mutant astrocytomas remain unclear. Here, we performed multiomics on matched initial and recurrent tumor samples from a cohort of 105 patients and overlaid the data with detailed clinical annotation. We identified overlapping features associated with malignant progression that are derived from three molecular mechanisms: cell cycling, tumor cell (de)differentiation and remodeling of the extracellular matrix. Together, they provide a rationale of the underlying biology of tumor malignancy. DNA methylation levels decreased over time, predominantly in tumors with malignant transformation, and co-occurred with poor prognostic genetic events. We identified a DNA methylation-based signature strongly associated with survival, which allows objective, molecular-based grading of IDH-mutant astrocytomas to aid clinical decision making. Our findings were validated on large, independent cohorts of IDH-mutant astrocytoma samples. Lastly, in this retrospective study, we found little effect of radiotherapy or chemotherapy on the molecular features associated with malignant progression.
Vallentgoed et al. (2025) studied this question.