Baseline 11C-methionine PET reflects the natural course of grade 2 oligodendrogliomas.

Objectives: The aim of the present study was to assess the usefulness of positron emission tomography (PET) with the amino acid tracer 11C-methionine (MET) as a predictor of time to progression (TTP) in patients with supratentorial grade 2 gliomas.

Methods: Twenty-seven patients with glioma grade 2 subjected to a baseline PET scan received no anti-tumour treatment except for a diagnostic operation, and were followed until tumour progression. The prognostic impact of the MET uptake and of other prognostic factors was studied.

Results: Twenty-five of the patients (93%) experienced tumour progression after a median of 103 weeks. Low uptake of MET was a predictor for long TTP in patients with oligodendrogliomas (p = 0.04) but not in astrocytomas/oligoastrocytomas. Other predictors for long TTP were oligodendroglioma histology (p = 0.009) and seizures as presenting symptom (p = 0.03). Favourable prognostic factors for overall survival were oligodendroglioma histology (p = 0.002) and good performance status (p = 0.03).

Conclusions: PET MET has a definite role in the therapeutic management of grade 2 gliomas. However, for the optimal use of PET MET in the clinical management of these patients, histological subclassification of the tumour is required.