Abstract
e12545 Background: Treatment of recurrent malignant glioma with bevacizumab (Avastin)/irinotecan yields high radiologic response rates. Avastin rapidly reduces contrast enhancement in MRI by restoring the blood-brain barrier. Therefore tumor evaluation using classical MacDonald's response criteria may be insufficient. In this retrospective study we aim to complement classical MR imaging criteria with T2 volumetry and FET-PET data to evaluate patients with recurrent malignant glioma treated with Avastin/irinotecan and to compare these imaging data to the patient's clinical performance status (CPS). Methods: 13 patients were treated with 10 mg/kg Avastin and 125 mg/kg irinotecan. MRI and FET-PET scans were performed in 8 weeks intervals, clinical examination was done biweekly. MR scanning included T1/T2 sequences with/without contrast application. Tumor volume was assessed using T2 and T1 post contrast volumetry applying standard MacDonald's response criteria. FET-PET was done applying a standard dose of 18F-fluoroethyltyrosine (18F-FET) using a standardized uptake threshold value of 1.6. CPS was assessed using a scoring system including Karnofsky performance index and clinical examination. Results: In the first follow-up PET results matched with T1 post contrast volumetry, T2 volumetry and CPS out of 13 patients in 9 (69%), 5 (38%) and 6 (46%) cases, respectively. 2 patients died before the second follow-up. Out of 11 patients PET results matched with T1 post contrast volumetry, T2 volumetry and CPS in 6 (55%), 5 (45%) and 6 (55%) cases, respectively. 4 nonresponsive patients with rapid clinical deterioration demonstrated early progress in PET-imaging which was not predictable on anatomic imaging. Conclusions: During the course of Avastin/irinotecan therapy PET-scan and MR imaging results are highly variable due to changes of tumor growth pattern (i.e., transformation to gliomatosis cerebri). PET scans predicted early tumor progression in nonresponding patients in this study group. No significant financial relationships to disclose.
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