Evaluation of 11C-methionine PET as a surrogate endpoint after treatment of grade 2 gliomas

Abstract

The aim of the present study was to assess the usefulness of positron emission tomography (PET) as a surrogate endpoint by analysing the uptake variability of 11C-methionine (MET) in follow-up scans.A total of 96 PET MET scans were re-evaluated in 32 patients with histologically confirmed supratentorial grade 2 gliomas. In untreated patients, all follow-up PET scans showed an increased tumour volume after median 68 weeks, but only 46% of cases had an increased hot spot uptake. An improved outcome was observed in patients with stable hot spot uptake per se (P = 0.07) and in combinations with minor increase in tumour volume (P = 0.02). After conventional therapy, 52% of PET scans showed a reduced hot spot uptake the first year and 43% were reduced after more than a year. Successful MET decline after therapy did not correlate with outcome. PET MET may be a promising surrogate endpoint after treatment of grade 2 gliomas. Evaluation of both hot spot activity and uptake volume on PET may strengthen the association with clinical outcome.

11C-l-Methionine Positron Emission Tomography in the Clinical Management of Cerebral Gliomas

“…However, the SUV did not increase above the pre-treatment level in this case [138]. Measuring both MET-defined tumor volume and MET-uptake has been recommended for following up on glioma patients [108,126]. A significant reduction in MET uptake and a semiquantitative index based on both MET uptake and MET-defined volume was noted in seven low-grade oligodendroglioma patients after chemotherapy with procarbazine, CCNU, and vincristine [126].…”

“…No such association was observed within the grade IV glioma group because of the overall poor prognosis in this subset [120]. Grade II oligodendrogliomas with a low methionine uptake were shown to have a longer time to progression of disease in another study [108]. In a multivariate analysis, MET uptake was found to be an independent significant prognostic factor in cerebral gliomas as compared to FDG [121] (Fig.…”

“…Herholz et al [147] have estimated a reduction rate in methionine-defined active tumor volume of approximately 2.4% per day in a case of anaplastic oligoastrocytoma after chemotherapy. In another study on 32 untreated grade II glioma patients, an increase in MET uptake or MET-defined volume on follow-up scans was associated with a reduced time to progression of disease [108]. In a study on METYPET scan performed 1 year after seed implantation of 125 I for brachytherapy of cerebral glioma, a significant reduction in MET uptake was evident but no significant change was noted in ten patients with FDG scan [129].…”

“…Low-grade gliomas that are difficult to identify on anatomic imaging modalities like CECT and MRI can also be seen in METYPET. For example, in a study by Ribom et al, 30 in 32 (94%) of low-grade gliomas had an increased methionine uptake, while only 12 in 32 (38%) showed contrast enhancement [107,108].…”

11C-Methionin-PET in der Neuroonkologie

“…Herholz et al [12] fanden unter kombinierter Chemotherapie hochgradig maligner Oligoastrozytome eine durchschnittliche t ä gliche Abnahme des Tumorvolumens von 2,4 % . In einer anderen Studie wurde bei Patienten mit Gliomen vom WHO-Grad II ein signifi kant l ä ngeres progressionsfreies Intervall beobachtet, bei im Verlauf in der 11 C-Methionin-PET stabilem " hot spot uptake " und Tumorvolumen -im Gegensatz zu einer Zunahme zumindest eines der beiden Parameter [29] .…”