NCCN updated its guidance to recommend cerebrospinal fluid (CSF)-based molecular tumor profiling for patients with high-grade glioma and glioblastoma when tissue biopsy is not feasible. The guideline update adds support for CSF testing as an adjunct diagnostic tool in biopsy-infeasible scenarios, including patients who are not appropriate surgical candidates or decline neurosurgical sampling. Belay Diagnostics said the change benefits its suite of assays run on a single CSF specimen from lumbar puncture, including its Summit 2.0 comprehensive genomic profiling panel, Ascent chromosomal instability assay, and Vantage MGMT promoter methylation assay. NCCN also highlighted that CSF profiling should be considered when diagnosis and treatment depend on molecular markers, citing examples such as H3K27-altered tumors. The update expands a growing list of CNS cancers where CSF-based testing is recommended, with prior additions including medulloblastomas and CNS lymphomas. Belay noted it published analytical and clinical validation for Summit 2.0 earlier this year, positioning the company to support adoption as centers move toward less invasive molecular workflows.