Cohort-level proportions of low-grade glioma (WHO grades I–II) in mixed glioma cohorts: a single-arm meta-analysis for epidemiological benchmarking and clinical trial design

Background Mixed-grade glioma surgical cohorts exhibit highly variable low-grade glioma (LGG) proportions across studies. This meta-analysis quantifies pooled LGG proportions to provide cohort-level epidemiological benchmarks for researchers, with applications in clinical trial design, health economics, and institutional benchmarking. Methods A single-arm meta-analysis of 191 cohort studies (25,847 patients) with Grade II numerators and denominators from Embase, MEDLINE, PubMed, and Scopus (PRISMA 2020) used Freeman-Tukey random-effects synthesis with Cochrane risk-of-bias assessments; subgroup analyses examined study design, geography, era, molecular specificity, and interventions; sensitivity analyses tested robustness. Results The pooled LGG proportion was 57% (95% CI: 52%-61%; I²=99%; n=191). Mixed LGG/high-grade gliomas (HGG) cohorts showed 41% (32%-50%; 45 studies, 6,847 patients) versus 82% (77%-88%) in pure WHO Grade II cohorts (25 studies). Surgery-only cohorts demonstrated 46% (33%-59%) versus 86% (74%-98%) with targeted therapies, and 93% (90%-96%) in randomized controlled trials. Sensitivity analyses confirmed stability (50%-62%). Conclusion In mixed-grade glioma cohorts, an LGG proportion approaching 60% may serve as a cohort-level epidemiological reference for understanding the historical grade composition of mixed surgical series. This meta-analysis primary value lies in applications such as clinical trial design, health economics and epidemiological modeling, and institutional benchmarking. Systematic Review Registration https://www.crd.york.ac.uk/prospero/ , identifier CRD420261323907.