Clinical Study
Comparative PET study using F-18 FET and F-18 FDG for the evaluation of patients with suspected brain tumour

https://doi.org/10.1016/j.jocn.2009.05.009Get rights and content

Abstract

The aim of this prospective pilot study in patients with suspected or known brain tumour was to establish the diagnostic value of O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) when compared to fluorine-18 fluorodeoxyglucose (FDG) PET. Twenty-five FET PET and FDG PET scans were performed on 21 consecutive patients within 24 months. Final malignant pathology included 11 glioma (eight low-grade, three high grade), two lymphoma, one olfactory ganglioneuroblastoma, one anaplastic meningioma. Benign pathology included two encephalitis and one cortical dysplasia. Definitive pathology was not available in three patients. The accuracy of PET was determined by subsequent surgical histopathology in 12 and clinical/imaging course in nine patients. Median follow-up period was 20 months. FET sensitivity was 93%, specificity 100%, accuracy 96%, positive predictive value (PPV) 100% and negative predictive value (NPV) 91%. FDG sensitivity was 27%, specificity 90%, accuracy 52%, PPV 80% and NPV 45%. FET PET is more accurate than FDG PET for detecting malignant brain lesions, especially low-grade gliomas.

Introduction

Fluorine-18 fluorodeoxyglucose (FDG) is the standard positron emission tomography (PET) tracer in oncological applications and has been widely used in brain tumour imaging in the past two decades.1 Increased glucose utilization is common in malignant gliomas. Consequently FDG uptake is generally high, especially in high grade glioma. The intensity of FDG uptake, as measured by a parameter termed the standardised-uptake value (SUV) has prognostic significance.2 However, the diagnostic accuracy of FDG in brain malignancy is hampered by the high glucose uptake in the normal brain tissue, limiting the detection of glioma, especially low-grade tumours which often show lower FDG accumulation than normal brain cortex. O-(2-[18F]fluoroethyl)-L-tyrosine (FET) has recently been developed as a radiotracer for PET brain tumour imaging.3 FET is an analogue of tyrosine that is actively transported into gliomas due to up-regulation of amino acid metabolism. FET has low uptake in inflammatory lesions and normal brain tissues, offering potential advantages over FDG.4 Recent studies showed that FET has a high accuracy in the initial diagnosis, recurrence assessment and radiotherapy planning of cerebral gliomas, especially when used in combination with MRI.5, 6, 7, 8, 9 FET was also shown to provide prognostically useful information in the assessment of low-grade glioma and small non-specific incidental brain lesions.10, 11

The aim of this prospective pilot study was to determine if FET PET imaging has an independent and incremental value to FDG PET in patients referred with the suspicion of active brain tumour in an Australian clinical context.

Section snippets

Patient population

Twenty-one patients, 14 males and seven females, underwent 25 paired FET PET and FDG PET scans for suspicion of brain tumour from 2004 to 2006. Each PET study pair was performed within a 14-day interval. Follow-up studies following treatment in four patients were included in this study, with three of them undergoing interval treatment with chemoradiation, radiation or surgical excision, respectively, following the initial PET scans. Age at the time of studies ranged from 24 to 69 years, with a

Results

The patient characteristics, including age, gender, pre-existing pathology, lesion location, reasons for PET scan, follow-up course and outcome, final pathology, FET and FDG accuracy, FET max SUVs and L/B ratios are summarised in Table 1. The PET scan results were classified into true positive (TP), false positive (FP), true negative (TN), false negative (FN) based on the initial qualitative assessment and validated by surgical histopathology (12 patients) or MRI and clinical course (nine

Discussion

This study demonstrated high accuracy of FET in the assessment of brain tumour, similar to previous reports in which the accuracy of stand-alone FET PET studies were compared to MRI using histology and clinical follow-up as a reference standard.5, 6, 7, 8, 9 Our study also compared FET PET with FDG PET. Recent studies have shown that FET PET has a high sensitivity and specificity of 88% in the assessment of newly diagnosed cerebral glioma as validated by final pathology,8 while the combined use

References (21)

  • A.L. Grosu et al.

    Reirradiation of recurrent high-grade gliomas using amino acid PET (SPECT)/CT/MRI image fusion to determine gross tumour volume for stereotactic fractionated radiotherapy

    Int J Rad Oncol Biol Phys

    (2005)
  • W. Chen

    Clinical applications of PET in brain tumors

    J Nucl Med

    (2007)
  • Di Chiro. Positron emission tomography using [18F] fluorodeoxyglucose in brain tumors. A powerful diagnostic and...
  • W.A. Weber et al.

    O-(2-[18F]fluoroethyl)-L-tyrosine and L-[methyl-11C]methionine uptake in brain tumours: initial results of a comparative study

    Eur J Nucl Med

    (2000)
  • F.C. Rau et al.

    O-(2-[18F]-fluoroethyl)-L-tyrosine (FET): a tracer for differentiation of tumour from inflammation in murine lymph nodes

    Eur J Nucl Med Mol Image

    (2002)
  • G. Popperl et al.

    Value of F-18 fluoroethyl-L-tyrosine PET for the diagnosis of recurrent glioma

    Eur J Nucl Med Mol Image

    (2004)
  • M. Weckesser et al.

    F-18 fluoroethyl-L-tyrosine PET in the clinical evaluation of primary brain tumour

    Eur J Nucl Med Mol Image

    (2005)
  • W. Rachinger et al.

    Positron emission tomography with F-18 fluoroethyl-L-tyrosine versus magnetic resonance imaging in the diagnosis of recurrent gliomas

    Neurosurgery

    (2005)
  • F.W. Floeth et al.

    Multimodal metabolic imaging of cerebral gliomas: positron emission tomography with F-18 fluoroethyl-L-tyrosine and magnetic resonance spectroscopy

    J Neurosurg

    (2005)
  • D. Pauleit et al.

    O-(2-[18F]fluoroethyl)-L-tyrosine PET combined with MRI improves the diagnostic assessment of cerebral gliomas

    Brain

    (2005)
There are more references available in the full text version of this article.

Cited by (0)

View full text