Gliomas are brain tumors with dismal prognoses. They are classified based on histology and molecular biomarkers that guide therapeutic decision-making. Somatostatin receptor subtype 2- (SSTR2) targeted radionuclide therapy has been suggested as a novel treatment approach for gliomas. However, SSTR2 expression in different glioma entities is still controversial. Therefore, a method is needed for in vivo detection of SSTR2 in gliomas, which would help in the selection of patients for radionuclide therapy.

Aims of this doctoral thesis were 1) to study the potential of positron emission tomography/computed tomography (PET/CT) to detect SSTR2 in gliomas in vivo, which would benefit the planning and follow-up of SSTR2-targeted radionuclide therapy, 2) to characterize SSTR2 expression in gliomas and explore its impact on survival, and 3) to evaluate serum glial fibrillary acidic protein (GFAP) and epidermal growth factor receptor (EGFR) as circulating biomarkers.

First, animal glioma models were studied for SSTR2 expression with PET/CT, autoradiography, and immunohistochemistry. Secondly, a prospective clinical study was conducted to examine the value of SSTR2 PET/CT and serum GFAP and EGFR in 27 patients with malignant glioma. Thirdly, SSTR2 expression and its impact on survival was retrospectively evaluated in 184 patients with glioma.

SSTR2 expression was detected in experimental gliomas, but the value of SSTR2-targeted PET/CT was limited. Also, in patients with malignant glioma, PET/CT could not predict SSTR2 expression in tumor tissue. In contrast, SSTR2 expression associated with oligodendrogliomas and improved prognoses, which was confirmed in the retrospective setup. Serum GFAP correlated with glioblastomas and tumor burden, whereas circulating EGFR was not related to tumor EGFR expression.

In conclusion, SSTR2 and serum GFAP are potential new biomarkers with diagnostic, prognostic, and/or therapeutic value. SSTR2 PET/CT has limited value in selecting glioma patients for radionuclide therapy.