Article
Differentiation of 74 intracerebral lesions with 18F-Fluorethyl-Tyrosin-PET
Untersuchung von 74 intrazerebralen Läsionen mit 18F-Fluorethyl-Tyrosin-PET
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Published: | April 23, 2004 |
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Outline
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Objective
In newly diagnosed intracerebral lesions serial biopsy is necessary to differentiate tumorous from non-tumorous lesions. The aim of this prospective study was to obtain the predictive value of metabolic imaging with PET using the amino acid 18F-Fluorethyl-L-Tyrosin (FET) in lesions being suspected as glial tumours.
Methods
Seventy-two Patients with 74 distinct lesions suspected to be gliomas underwent evaluation with contrast-enhanced MRI and FET-PET. A positive result indicating tumour tissue was assumed if PET showed an increased amino acid uptake with a minimum tumour/brain ratio of 1.6 and a diameter of at least 1 cm. All lesions underwent a subsequent neuronavigated serial biopsy in different areas with special attention to PET-positive areas. Biopsy locations were labelled with titanium pellets.
Results
Biopsies from 99 different areas within the 74 lesions were obtained. In 60 areas both MRI and FET-PET indicated tumour tissue and the biopsies confirmed glioma in 56 areas (93 % positive predictive value). In 39 areas only MRI showed tumour features, but FET-PET was negative with no increased uptake. Only in 10 of these areas biopsy revealed glioma tissue (26 % positive predictive value). Regarding the 74 lesions as a whole, 58 lesions were FET-PET positive and biopsy confirmed the diagnosis of glioma in 56 cases (97 % specificity). In 2 lesions FET-PET was false positive. 16 lesions were FET-PET negative and in 10 cases no tumour tissue was found in the biopsies (63 % sensitivity). In 6 of these lesions glioma tissue was found, thus FET-PET was false negative. In 6 of 62 biopsy proven gliomas (10 %) there was no apparent uptake of the amino acid FET.
Conclusions
FET-PET investigation is very specific (3 % false positive results) but not very sensitive (37 % false negative results) in the prediction of the result of biopsy in newly diagnosed lesions suspected to be gliomas. In case of a positive FET-PET, biopsy should be taken from the PET-positive areas, since this strategy will lead to tumour diagnosis in nearly all cases (93 %).