High-grade glioma before and after treatment with radiation and Avastin: initial observations

Abstract

We evaluate the effects of adjuvant treatment with the angiogenesis inhibitor Avastin (bevacizumab) on pathological tissue specimens of high-grade glioma. Tissue from five patients before and after treatment with Avastin was subjected to histological evaluation and compared to four control cases of glioma before and after similar treatment protocols not including bevacizumab. Clinical and radiographic data were reviewed. Histological analysis focused on microvessel density and vascular morphology, and expression patterns of vascular endothelial growth factor-A (VEGF-A) and the hematopoietic stem cell, mesenchymal, and cell motility markers CD34, smooth muscle actin, D2-40, and fascin. All patients with a decrease in microvessel density had a radiographic response, whereas no response was seen in the patients with increased microvessel density. Vascular morphology showed apparent "normalization" after Avastin treatment in two cases, with thin-walled and evenly distributed vessels. VEGF-A expression in tumor cells was increased in two cases and decreased in three and did not correlate with treatment response. There was a trend toward a relative increase of CD34, smooth muscle actin, D2-40, and fascin immunostaining following treatment with Avastin. Specimens from four patients with recurrent malignant gliomas before and after adjuvant treatment (not including bevacizumab) had features dissimilar from our study cases. We conclude that a change in vascular morphology can be observed following antiangiogenic treatment. There seems to be no correlation between VEGF-A expression and clinical parameters. While the phenomena we describe may not be specific to Avastin, they demonstrate the potential of tissue-based analysis for the discovery of clinically relevant treatment response biomarkers.

Fig. 1

T2- (left) and T1- (right) weighted MRI images of patient 1. (a) Resection cavity with peripheral contrast enhancement. (b) Persistent minimal peripheral enhancement and increase of periventricular and left frontoparietal T2 signal. (c) Multiple enhancing nodules and a dominant right frontal lobe mass with markedly increased surrounding T2 hyperintense signal.

Fig. 2

T2- (left) and T1- (right) weighted MRI images of patient 2. (a) Nodular enhancing tumor around surgical cavity margins and T2 signal abnormalities in the frontal lobes and bilateral anterior temporal lobes. (b) Decrease of the nodular enhancing component and frontal T2 signal intensity. (c) Increase in left frontal and temporal lobe enhancement and new involvement of the left basal ganglia and caudate with increased T2 signal and increased mass effect.

Fig. 3

Histological findings in patient 2 (upper row before treatment, lower row after treatment). (a, f) CD34 highlights vascular arcades prior to Avastin and increased tumor cell staining after. (b, g) Vascular endothelial growth factor–A in vascular basement membranes and rare tumor cells. (c, h) D2-40 expression is more diffuse after treatment. (d, i) Fascin highlights a similar percentage of tumor cells before and after treatment. (e, j) Smooth muscle actin labels vascular smooth muscle cells before and the majority of tumor cells after treatment. Original magnification: 40×.

Fig. 4

Histological findings in patient 1 (upper row before treatment, lower row after treatment). (a, f) CD34 immunostain highlights glomeruloid proliferations; after treatment, tumor cells are also labeled. (b, g) Vascular endothelial growth factor–A immunostain labels basement membranes of tumor blood vessels. (c, h) D2-40 expression is increased after Avastin treatment. (d, i) Fascin highlights invading tumor cells. (e, j) Smooth muscle actin labels only vascular smooth muscle cells before but tumor cells after treatment. Original magnification: 40×.