Abstract
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Objectives Amino acid PET with [18F]FET was previously shown to improve the differentiation of tumor recurrence from unspecific post-therapeutic tissue changes in malignant glioma. The aim of the present study was to evaluate factors predicting the recurrence pattern in patients with newly diagnosed glioblastoma (GBM) after combined radiotherapy (RT) and oral temozolomide (TMZ).
Methods 79 patients with newly diagnosed GBM treated with RT plus TMZ followed by maintenance TMZ cycles were retrospectively analyzed. Recurrence was assessed by means of PET with [18F]-FET in all patients. Additionally, MGMT methylation status was evaluated in 49 patients.
Results 34.2 % of the patients did not relapse during follow-up (median 595 days) whilst 49.4 % had an in-field recurrence, 12.7 % an ex-field recurrence and 3.8 % had a recurrence at the RT field margin. MGMT status was shown to be a strong predictor for progression-free- and overall survival. In MGMT methylated patients, the 1-yr/2-yr Overall-Survival was 93% / 77% compared to 68% / 10% in MGMT not methylated patients. 57% of the MGMT methylated population relapsed compared to 67% of the MGMT not-methylated patients. 62% (10/16) of the MGMT methylated patients had an in-field recurrence compared to 86% (12/14) MGMT not methylated patients (p = 0.23).
Conclusions FET-PET is a reliable tool to early detect recurrence after radiotherapy and to differentiate from postradiogenic changes. The incidence of in-field recurrence as well as the prognostic outcome of combined radio-chemotherapy with TMZ in GBM seems to be associated with MGMT methylation status