Belay Diagnostics Summit™ Informed Clinical Decisions in 93% of Cases in Large Real-World CNS Study
New peer-reviewed study from UT Southwestern Medical Center shows Summit found clinically significant variants in more than half of cytology-negative cases.
CHICAGO, May 6, 2026 /PRNewswire/ — A new peer-reviewed study shows that the Belay Summit cerebrospinal fluid (CSF)-based liquid biopsy test informed clinical decisions in 93% of cases involving suspected or confirmed central nervous system (CNS) cancer, including in patients where standard cytology results returned negative.
In a real-world cohort of patients with suspected or confirmed CNS cancer, standard CSF cytology was negative in 86% of specimens. The study, published in Cancers, evaluated Summit across 123 specimens from 120 patients at UT Southwestern Medical Center. Summit informed diagnosis, treatment selection, response monitoring, or confirmed absence of malignancy in 93% of cases. The full study is available here.
Detection Where Cytology Falls Short
Summit found clinically significant variants in 56% of cytology-negative specimens and detected variants in every cytology-positive case. Beyond improved sensitivity, Summit delivers what cytology cannot: molecular characterization to guide treatment selection and response monitoring. Summit positivity appeared unaffected by corticosteroid use, a known confounder for cytology.
Identifying and Monitoring Leptomeningeal Disease
Summit’s quantitative variant allele frequency (VAF) measurement yielded additional molecular information beyond what cytology provides. In this cohort, all specimens with VAF above 5% were associated with confirmed leptomeningeal disease (LMD), including two cases initially thought to be parenchymal brain metastases. Serial testing in two patients tracked treatment response, with falling VAF in one patient corresponding to clinical improvement and stable VAF in another corresponding to lack of response.
“This study documents what we observed across more than 120 patients at UT Southwestern: Summit informed clinical decisions in 93% of cases, including in patients where cytology returned negative. For patients with leptomeningeal disease, VAF measurements gave us a quantitative way to support diagnosis and longitudinal disease assessment beyond cytology and imaging alone. Summit has become essential to how I approach diagnostic uncertainty in CNS cancer,” said Michael Youssef, MD, neuro-oncologist at Houston Methodist Oncology Partners, Texas Medical Center, and first author of the study, which was conducted during his tenure at UT Southwestern Medical Center.
Since this study was conducted, Belay launched Summit™ 2.0, which evaluates 520 genes for SNVs and indels, 62 genes for copy number variants, 28 genes for fusions, plus tumor mutation burden (TMB) and microsatellite instability (MSI), with clinical sensitivity of 96% and specificity of 98% for CNS malignancies.
About Belay Diagnostics – Belay Diagnostics is a Chicago-based laboratory dedicated to serving patients and the clinicians who care for them. Using licensed technology developed through more than 10 years of scientific research at Johns Hopkins University, Belay has developed three proprietary CSF liquid biopsy tests — Belay Summit™ 2.0, Belay Ascent™, and Belay Vantage™ — developed and validated to help inform the diagnosis and management of primary and secondary CNS malignancies. Belay’s tests provide clinicians with comprehensive molecular insights from a standard lumbar puncture. No tissue required. For more information, visit belaydiagnostics.com.