Cerebral and tumoral blood flow in adult gliomas: a systematic review of results from magnetic resonance imaging

Objective: Blood flow is the rate of blood movement and relevant to numerous processes, though understudied in gliomas. The aim of this review was to pool blood flow metrics obtained from MRI modalities in adult supratentorial gliomas. Methods: MEDLINE, EMBASE and the Cochrane database were queried 01/01/2000-31/12/2019. Studies measuring blood flow in adult Grade II-IV supratentorial gliomas using dynamic susceptibility contrast (DSC) MRI, dynamic contrast enhanced MRI (DCE-MRI) or arterial spin labelling (ASL) were included. Absolute and relative cerebral blood flow (CBF), peritumoral blood flow and tumoral blood flow (TBF) were reported. Results: 34 studies were included with 1415 patients and 1460 scans. The mean age was 52.4 +/- 7.3 years. Most patients had glioblastoma (n = 880, 64.6%). The most common imaging modality was ASL (n = 765, 52.4%) followed by DSC (n = 538, 36.8%). Most studies were performed pre-operatively (n = 1268, 86.8%). With increasing glioma grade (II vs IV), TBF increased (70.8 vs 145.5 ml/100 g/min, p < 0.001) and CBF decreased (85.3 vs 49.6 ml/100g/min, p < 0.001). In Grade IV gliomas, following treatment, CBF increased in ipsilateral (24.9 +/- 1.2 vs 26.1 +/- 0.0 ml/100g/min, p < 0.001) and contralateral white matter (25.6 +/- 0.2 vs 26.0 +/- 0.0ml/100 g/min, p < 0.001). Conclusion: Our findings demonstrate that increased mass effect from high-grade gliomas impairs blood flow within the surrounding brain that can improve with surgery. Advances in knowledge: This systematic review demonstrates how mass effect from brain tumours impairs blood flow in the surrounding brain parenchyma that can improve with treatment.