gms | German Medical Science

Objective: Treatment suggestions and prognosis of high-grade glioma patients depends on the expression of molecular markers as MGMT promotor methylation status. Moreover, the value of IDH1R mutation status for the differentiation between primary and secondary glioblastoma (GBM) becomes evident. Assessment of these markers is obtained after obtaining a specimen via stereotactic or open surgery. The purpose of this study was to analyze, whether stereotactic surgery displays different results from open surgical sample acquisition, or not.

Method: In our department, between 2011 and 2013 a total of 22 patients were diagnosed with anaplastic astrocytoma (AA) or glioblastoma by stereotactic surgery and afterwards underwent surgical resection of their tumor. Patient and tumor characteristics, surgical complications and histopathological markers were prospectively included in the database. MGMT promotor analysis was carried out by PCR, IDH1R mutation analysis by immunohistochemistry.

Results: Of the 22 patients analyzed, 9 were of female sex (40.9 %), median age was 57.5 years (IQR 47.8 - 66.3 years), 21 patients (95.5 %) suffered from newly diagnosed glioma, while 1 patient (4.5 %) had a known history of GBM. Median number of stereotactic samples obtained was 17 (IQR 12.5 - 21). Histopathological diagnosis after stereotactic surgery was GBM in 19 cases (86.4 %) and AA in 3 patients (13.6 %). MGMT promotor analysis of stereotactic samples revealed promotor methylation in 10 patients (45.5 %), an unmethylated promotor in 10 patients (45.5 %) and inconclusive results in 2 patients (9 %). These results were confirmed by MGMT promotor analysis of samples acquired by open surgery in all but one patient, where an inconclusive MGMT promotor methylation analysis was obtained, instead of a methylated promotor as diagnosed in the stereotactically obtained specimen. 3 patients (13.7 %) displayed IDH1 receptor mutation in stereotactic samples. All IDH1 receptor mutation analysis was confirmed in samples acquired in open tumor resection.

Conclusions: Here, we describe that the sample acquisition obtained by small-sized stereotactic biopsies reliably provides information on both molecular markers. The profile of both markers remains unchanged, whether analyzed in stereotactically or surgically obtained samples concluding that treatment decisions may be based on the molecular profile obtained by stereotactic surgery without the need for confirmation in open surgery.