798 Accuracy of Image-guided Stereotactic Brain Biopsy in the Diagnosis of Glioma: Comparison of Biopsy and Open Resection Specimen

Abstract

INTRODUCTION: Tissue heterogeneity and rapid tumor progression may decrease the accuracy and prognostic value of stereotactic brain biopsy in the diagnosis of gliomas. Correct tumor grading is therefore dependent on accuracy of biopsy needle placement. The accuracy of frameless and frame-based techniques in the diagnosis and grading of glioma remains unstudied. METHODS: The diagnoses of 21 astrocytic brain tumors were derived using image-guided stereotactic biopsy (12 frame-based, 9 frameless) and followed by open resection of the lesion 1.5 months (0.5–4 mo) later. The histological diagnoses yielded by biopsy were compared with subsequent histological diagnosis from open tumor resection. RESULTS: Stereotactic biopsy histology accurately represented the greater lesion at open resection a median of 45 days later in 16 patients (76%) and correctly guided therapy in 19 (91%). Biopsy accuracy of frameless versus frame-based stereotaxy was similar (89 versus 66%, P = 0.21). In 3 patients (14%), biopsy specimens were adequate to diagnose glioma; however, histology was insufficient for definitive tumor grading (grade III versus IV). Anaplastic oligodendroglioma (ODG) was undergraded as low-grade ODG in 1 patients (5%). Biopsy of new-onset GBM yielded necrosis/gliosis and was called nondiagnostic in one patient. Tumors >50 cm3 were eightfold less likely to accurately represent the grade of the entire lesion at resection compared with lesions <50 cm3 (OR, 8.8; 95% CI, 0.9–100; P = 0.05). CONCLUSION: Both frameless and frame-based magnetic resonance imaging-guided stereotactic brain biopsy are safe and accurately represent the larger glioma mass sufficiently to guide subsequent therapy. The diagnostic accuracy of frameless stereotactic brain biopsy is equivalent to the frame-based technique in the diagnosis and grading of glioma. Glioma volume >50 cm3 may be a negative prognostic indicator of biopsy accuracy.