Diagnostic accuracy of 201Thallium-SPECT and 18F-FDG-PET in the clinical assessment of glioma recurrence

Purpose Reliable differential diagnosis between tumour recurrence and treatment-induced lesions is required to take advantage of new therapeutic approaches to recurrent gliomas. Structural imaging methods offer a high sensitivity but a low specificity, which might be improved by neurofunctional imaging. This study aimed to test the hypothesis that incorporation of 18- fluoro-deoxy-glucose positron emission tomography ( FDG-PET) increases the accuracy of this differential diagnosis obtained with Tl-201 chloride-single-photon emission computed tomography ( Tl-201- SPECT). Materials and methods Seventy-six patients ( mean age 47.72 +/- 16.19 years) under suspicion of glioma recurrence, 42% with low-grade and 58% with high- grade lesions, were studied by Tl-201- SPECT and FDG- PET, reporting results under blinded conditions using visual analysis. Tumour was confirmed by histological confirmation ( 23 patients) or clinical and structural neuroimaging follow- up ( mean of 2.6 years). Results This population had a high disease prevalence ( 72%). Globally, highest sensitivity was obtained using Tl-201- SPECT assessed with MRI ( 96%) and highest specificity using FDG-PET + MRI ( 95%). FDG-PET appeared slightly better for confirming tumour recurrence, whereas Tl-201- SPECT was superior for ruling out possible recurrence ( disease present in 38% of FDG- PET negative explorations). In the high- grade subgroup, there were no false-positive examinations ( specificity: 100%), but sensitivity differed among techniques ( Tl-201- SPECT: 94%; 201Tl- SPECT + MRI: 97%; FDG- PET + MRI: 83%). In the low-grade subgroup, Tl-201-SPECT+ MRI showed highest sensitivity ( 95%) and lowest posttest negative probability ( 9%); FDG- PET + MRI offered highest specificity ( 92%) with a posttest negative probability of 35%. Conclusions FDG-PET does not clearly improve the diagnostic accuracy of Tl-201- SPECT, which appears to be a more appropriate examination for the diagnosis of possible brain tumour recurrence, especially for ruling it out.