Abstract
Simple SummaryGlioblastomas and brain metastases are the most common malignant intracerebral tumors in adults and are often difficult to differentiate using conventional MRI. Common to both is contrast enhancement on T1w post-Gd sequences and perilesional T2 hyperintensity, which in glioblastomas corresponds to diffuse tumor infiltration rather than to edema alone. Characterization of perifocal T2 hyperintensity in glioblastoma has been poor using MRI, and tumor recurrences frequently occur in these areas. Using a novel diffusion microstructure imaging (DMI) approach, we observed that in metastases, perilesional T2 hyperintensity is more likely due to edema alone with a higher fraction of free water and reduced cellular compartments compared to glioblastomas. DMI might be a powerful diagnostic tool, as it could be used to distinguish metastases from GBM, as well as characterizing perifocal T2 hyperintensity in GBM.Purpose: Glioblastomas (GBM) and brain metastases are often difficult to differentiate in conventional MRI. Diffusion microstructure imaging (DMI) is a novel MR technique that allows the approximation of the distribution of the intra-axonal compartment, the extra-axonal cellular, and the compartment of interstitial/free water within the white matter. We hypothesize that alterations in the T2 hyperintense areas surrounding contrast-enhancing tumor components may be used to differentiate GBM from metastases. Methods: DMI was performed in 19 patients with glioblastomas and 17 with metastatic lesions. DMI metrics were obtained from the T2 hyperintense areas surrounding contrast-enhancing tumor components. Resected brain tissue was assessed in six patients in each group for features of an edema pattern and tumor infiltration in the perilesional interstitium. Results: Within the perimetastatic T2 hyperintensities, we observed a significant increase in free water (p < 0.001) and a decrease in both the intra-axonal (p = 0.006) and extra-axonal compartments (p = 0.024) compared to GBM. Perilesional free water fraction was discriminative regarding the presence of GBM vs. metastasis with a ROC AUC of 0.824. Histologically, features of perilesional edema were present in all assessed metastases and absent or marginal in GBM. Conclusion: Perilesional T2 hyperintensities in brain metastases and GBM differ significantly in DMI-values. The increased free water fraction in brain metastases suits the histopathologically based hypothesis of perimetastatic vasogenic edema, whereas in glioblastomas there is additional tumor infiltration.
Highlights
Glioblastoma (GBM; IDH-wildtype (IDH-wt)) is the most common malignant primary intracerebral tumor in adults [1]
Out of 52 patients presenting with contrast-enhancing intracranial mass lesions, 17 patients (8 female; mean age: 63.5; SD 11.8, range 47.1–85.6 years) with histologically verified brain metastases and 19 patients with GBM (IDH wildtype, 9 female; mean age: 66.4; SD 14.1, range 41.8–88.0 years) underwent presurgical MRI
Corticosteroids had been administered in 7 patients in the GBM group and 6 patients with metastases
Summary
Glioblastoma (GBM; IDH-wildtype (IDH-wt)) is the most common malignant primary intracerebral tumor in adults [1]. Tumor infiltration in GBM usually extends well beyond the contrast-enhancing and even T2 hyperintense tumor portions, and to date has been difficult to characterize by conventional MR imaging. The assumption that the contrast-enhancing margin of GBM does not correspond to its tumor boundary is supported by the fact that most tumor recurrences occur within peripheral T2/FLAIR hyperintense areas [3]. It is, necessary to further characterize infiltrative GBM tumor components by MRI. Cerebral metastases with marginal contrast enhancement, perifocal T2/hyperintensity, and solitary localization often cannot be reliably distinguished from high-grade gliomas such as GBM by conventional MR imaging
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