Meningioma-Associated FLAIR Hyperintensity Is Only Partly Explained by Tumor Volume in 1,000 Public BraTS Segmentations
Peritumoral FLAIR hyperintensity is clinically important in meningioma, but it is often treated as a qualitative companion to tumor size rather than as a quantitatively separable imaging phenotype. We analyzed 1,000 public BraTS 2023 pre-operative meningioma training segmentations to measure enhancing tumor, non-enhancing or necrotic core, and peritumoral FLAIR hyperintensity volumes from expert-refined masks. Edema was present in 536 cases. Median segmented tumor volume was 9.21 ml (IQR 2.08-31.17), while median edema volume was 0.08 ml (IQR 0.00-23.54), reflecting a sharply zero-inflated and right-tailed distribution. Among cases with nonzero edema, log edema volume increased with log tumor volume (Spearman rho = 0.47, p = 3.6e-30), and a heteroskedasticity-robust log-log model estimated an approximately proportional scaling exponent of 0.97 (95% CI 0.80-1.14). However, tumor volume explained only 21.6% of edema-volume variance. The 90th percentile edema-to-tumor ratio was 3.87; these high-ratio cases had far greater edema burden despite smaller median tumor volume than the remaining edema-positive cohort. These findings argue that meningioma-associated FLAIR hyperintensity should not be reduced to tumor size. Simple compartment volumes provide a useful baseline, but edema burden appears to encode additional biology, anatomy, or acquisition-context effects that require clinical metadata and richer imaging models.
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This paper asks a clean baseline question using a large public resource: in BraTS 2023 pre-operative meningioma segmentations (n=1,000), how strongly is peritumoral FLAIR hyperintensity (“edema”) volume explained by tumor volume? The main quantitative results—heavy zero inflation (edema absent in ~46%), a moderate monotonic association among edema-positive cases (Spearman ρ≈0.47), and a log–log scaling exponent near 1 with robust SEs—are plausible and, if computed as stated, support the central claim that edema is not reducible to tumor size. The reported low explained variance (R²≈0.216) and the high upper-tail edema-to-tumor ratios provide a straightforward argument that edema burden contains additional information beyond size. The main weakness is that the analysis is under-specified for reproducibility and vulnerable to dataset/label-definition artifacts. The BraTS “peritumoral FLAIR hyperintensity” compartment may include heterogeneous phenomena (true vasogenic edema vs gliosis, CSF/partial volume, postoperative change excluded but other confounds remain), and multi-site acquisition variability plus segmentation error can induce both zero inflation and heteroskedasticity. Modeling choices (conditioning on edema>0, handling of zeros, volume computation details, voxel spacing, connected-component filtering, and whether tumor volume includes enhancing+core or also non-enhancing regions) are not described here, and could materially change the exponent and R². The conclusion (“only partly explained by tumor volume” and “likely encodes additional biology/anatomy/acquisition context”) is directionally justified by the reported statistics, but causal/biologic interpretation is not yet supported without clinical covariates, site effects, and sensitivity analyses for label noise and zero handling.