Role of [11C] methionine positron emission tomography in the diagnosis and prediction of survival in brain tumours

Abstract

Objective[11C] methionine (MET) positron-emission tomography (PET) is a useful diagnostic and therapeutic tool in neuro-oncology. The aim of this study was to evaluate the relationship between MET uptake and the histopathological grade in both primary brain tumours and brain metastases. A secondary goal was to assess the relationship between MET uptake and patients’ survival after surgery. MethodsWe reviewed a consecutive series of 43 PET studies performed at our institution. Out of the 43 patients studied, 35 harboured primary brain tumours (3 grade I, 12 grade II, 7 grade III and 13 grade IV) and 8 patients had brain metastases. We measured the tumour/cortex ratio (T/C ratio) on each PET study and we investigated the correlations among the tracer uptake, tumour grade, tumour type, MRI parameters and outcome. ResultsThe mean T/C ratio was 1.8±0.9 for benign lesions and low grade gliomas (grade I and II) and 2.7±1 for high grade gliomas (grade III and IV). In brain metastases it was 2.5±0.7, with a significant difference in MET uptake between low and high grades gliomas (P=0.03). There was no statistically significant difference among all different histologic types.We found that both contrast enhancement and perfusion studies correlate with MET uptake in brain tumours. Moreover, in Kaplan–Meier curves, the T/C ratio adversely affects long term survival in patients with brain tumours (P=0.01). ConclusionsMET PET appears to be useful in diagnosis and evaluation of potential malignancy in brain tumours. MET uptake is also related with the overall survival in patients with brain tumours. Nevertheless, further studies are needed in order to define its possible clinical implications in identifying patients at high risk of tumour progression or resistance to therapy.