A Methionine PET Targeting for Gamma Knife Radiosurgery used to Treat Recurrent Malignant Gliomas at Inoperable Stage

Abstract

Purpose: The current study investigates the usefulness of metabolic positron emission tomography (PET) imaging (in particular with 11C-methionine (MET)), for target definition during gamma knife radiosurgery (GKRS) of locally multirecurrent malignant glioma at inoperable stage. Patients and Methods: We retrospectively evaluated the results of GKRS with MET-PET targeting for 24 adult focally recurrent inoperable malignant gliomas treated at the Erasme Gamma Knife Center between 2007 and 2018. We evaluated the type of tumour progression (local vs remote), progression-free survival (PFS), overall survival (OS) and toxicity after MET-PET targeting of GKRS for these 24 patients. Results: The median PFS after GKRS for the 24 patients with malignant gliomas was 5.5 (2-46) months and 4.5 (3-10), 4.5 (2-8) and 13.5 (2-46) months for glioblastoma, anaplastic glioma and grade II glioma patients, respectively. The median OS from the GKRS procedure for patients with recurrent glioblastomas (n=12) was 18 (6-45) months, 8 (6-184) months for anaplastic gliomas (n=6), and 22 (16-65) months for grade II gliomas (n=6). All patients with grade III and II multirecurrent gliomas (n=12) showed an early favourable local metabolic response, while this response was observed only in 6/12 of the glioblastomas. However, the majority (9/12=75%) of these grade II/III glioma patients further developed new lesions. GKRS treatment was associated with diverse chemotherapies in more than 50% (13/24) of cases. Post-GKRS radio-necrosis was observed in only one patient. Conclusion: Based on a limited series of 24 patients, our study shows, for the first time, the GKRS-induced metabolic response in focally recurrent inoperable malignant gliomas. GKRS could be part of the multidisciplinary approach for multirecurrent malignant gliomas that cannot be anymore treated by surgery.