MR cerebral blood volume maps correlated with vascular endothelial growth factor expression and tumor grade in nonenhancing gliomas

Abstract

Background and purpose: Relative cerebral blood volume (rCBV) measurements derived from perfusion-weighted imaging (PWI) may be useful to evaluate angiogenesis and preoperatively estimate the grade of a glioma. We hypothesized that rCBV is correlated with vascular endothelial growth factor (VEGF) expression as marker of the angiogenic stimulus in presumed supratentorial low-grade gliomas (LGGs).

Methods: From February 2001 to February 2004, we examined 20 adults (16 men, four women; mean age 36 years; range, 23-60 years) with suspected (nonenhancing) supratentorial LGG on conventional MR imaging. Preoperative MR imaging used a dynamic first-pass gadolinium-enhanced, spin-echo echo-planar PWI. In heterogeneous tumors, we performed stereotactic biopsy in the high-perfusion areas before surgical resection. Semiquantitative grading of VEGF immunoreactivity was applied.

Results: Nine patients had diffuse astrocytomas (World Health Organization grade II), and 11 had other LGG and anaplastic gliomas. In patients with heterogeneous tumors on PWI, the high-rCBV focus had areas of oligodendroglioma or anaplastic astrocytoma on stereotactic biopsy, whereas the surgical specimens were predominantly astrocytomas. Anaplastic gliomas had high rCBV ratios and positive VEGF immunoreactivity. Diffuse astrocytomas had negative VEGF expression and mean rCBV values significantly lower than those of the other two groups. Three diffuse astrocytomas had positive VEGF immunoreactivity and high rCBV values.

Conclusion: Our results confirmed the correlation among rCBV measurements, VEGF expression, and histopathologic grade in nonenhancing gliomas. PWI may add useful data to the preoperative assessment of nonenhancing gliomas. Its contribution in predicting tumor behavior and patient prognosis remains to be determined.

Fig 1.

Anaplastic astrocytoma. Axial enhanced T1–weighted image demonstrates a right frontal, nonenhancing lesion (A). rCBV map shows a markedly elevated rCBV of 3.6, which is consistent with biopsy-proved anaplastic astrocytoma (B). Immunohistochemical staining (400×) with monoclonal antibody against VEGF reveals strong cellular and endothelial positivity (C).

Fig 2.

Diffuse astrocytoma. Axial enhanced T2-weighted image shows a left frontal nonenhancing lesion (A). rCBV map shows an obviously reduced rCBV of 0.72, which is consistent with biopsy-proved diffuse astrocytoma (WHO grade II). Immunohistochemical staining (400×) with the monoclonal antibody against VEGF is negative (C).

Fig 3.

Diffuse astrocytoma. Axial enhanced T1-weighted image shows a left frontal nonenhancing lesion (A). rCBV map shows an elevated rCBV of 1.9 (B). Histologic section (400×) reveals a diffuse astrocytoma (WHO grade II), but VEGF staining shows strong cellular and endothelial positivity (C).

Fig 4.

Anaplastic astrocytoma. Coronal enhanced T1-weighted image shows a heterogeneous left frontal lesion (A). rCBV map demonstrates a focal area with a high rCBV of 3.11. Histologic section (400X) of this focus is consistent with biopsy-proved anaplastic astrocytoma, and VEGF staining shows strong cellular and endothelial positivity (C).