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Low-grade glioma makes up 57% of mixed-grade glioma surgical cohorts, meta-analysis findsNew data clarifies the prevalence of low-grade glioma tumors

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Key Takeaway
Interpret LGG proportions as cohort-dependent benchmarks, not fixed estimates.

This meta-analysis pooled data from 191 cohort studies comprising 25,847 patients to estimate the proportion of low-grade glioma (LGG) within mixed-grade glioma surgical cohorts. The overall pooled LGG proportion was 57% (95% CI 52%-61%).

Estimates differed substantially by cohort definition. In mixed LGG/HGG cohorts (45 studies, 6,847 patients), the pooled LGG proportion was 41% (95% CI 32%-50%). In pure WHO Grade II cohorts (25 studies), it was 82% (95% CI 77%-88%). Surgery-only cohorts had a pooled proportion of 46% (95% CI 33%-59%), while cohorts involving targeted therapies had 86% (95% CI 74%-98%) and randomized controlled trials had 93% (95% CI 90%-96%).

The authors report high heterogeneity (I2=99%) as a limitation. Adverse events, follow-up duration, funding, and conflicts of interest were not reported. The analysis addresses epidemiological proportions rather than clinical outcomes, and no comparator was specified.

The findings provide epidemiological benchmarks that may inform clinical trial design, health economics, and institutional benchmarking. Because of the high heterogeneity and the descriptive nature of the analysis, these proportions should be interpreted as context-dependent estimates rather than fixed parameters.

How this fits prior evidence

This meta-analysis provides pooled epidemiological benchmarks for LGG proportions in mixed-grade glioma cohorts, complementing prior coverage of multiparametric MRI and image-guided neurointerventions for brain tumor management and surveillance. It also extends the context of molecular characterization work, such as unsupervised clustering of glioma RNAseq data, by quantifying the histological composition of surgical cohorts. The wide variation by cohort definition (41% to 93%) underscores that LGG proportion depends heavily on study design and eligibility criteria, consistent with the need for validation noted in prior molecular clustering findings.

When doctors treat patients with mixed-grade glioma, they often need to know exactly what kind of tumors they are dealing with. This new analysis looked at data from over 25,000 patients across 191 different studies to find clear patterns in these tumor types.

The results show that about 57% of tumors in mixed groups were low-grade gliomas. However, the numbers changed significantly depending on the setting. For example, patients in randomized controlled trials were much more likely to have low-grade tumors, with a rate of 93%. In contrast, those in surgery-only groups had a lower rate of 46%.

While these findings provide a helpful benchmark for doctors to use when planning treatments and designing future studies, the data comes from a very diverse set of sources. Because the original studies were so different from one another, the results should be used as a guide for understanding population trends rather than a specific prediction for any individual patient.

What this means for you:
Over half of tumors in mixed-grade glioma groups are low-grade, but this varies greatly by treatment setting.

Common questions

What percentage of mixed-grade glioma cases are low-grade?

The study found that 57% of tumors in mixed glioma cohorts were low-grade gliomas. This number helps doctors establish a baseline for what to expect when treating patients with mixed-grade tumors.

How does the tumor type change based on the type of treatment?

The proportion of low-grade gliomas changed based on the setting. For example, 86% of cases in groups receiving targeted therapies were low-grade, while only 46% were low-grade in groups receiving surgery only.

What did the study find for patients in clinical trials?

In randomized controlled trials, the proportion of low-grade gliomas was very high, at 93%. This helps researchers understand the types of patients who typically participate in these specific types of studies.

Study Details

Study typeMeta analysis
EvidenceLevel 1
PublishedOct 2026
View Original Abstract ↓
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. 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. 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%). 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. https://www.crd.york.ac.uk/prospero/, identifier CRD420261323907.
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