Abstract
1686
Objectives: PET-CT using 11C-Methonine ([11C]-MET) has been reported to detect brain tumors with high Sensitivity & Specificity. In this study we have evaluated the potential of [11C]-MET in recurrent Cerebral tumors. Comparison of F18-FDG with [11C]-MET has also been done.
Methods: 96 subjects of brain tumor treated by surgery, chemotherapy or radiotherapy were subjected to [18F]-FDG, [11C]-MET & MRI scan. The lesion were analysed semi-quantitatively using tumor to normal contralateral ratio. Diagnosis was confirmed by surgery, stereotactic biopsy, clinical follow up, MRI or CT scans.
Results: Tumor recurrence was found in 8 out of 33 patients on [F-18] FDG scan while [11C]-MET was able to detect recurrence in 27 out of 33 patients in low grade gliomas. 3 of these patients were false positive for presence of recurrence of tumor & later found to be harbouring necrosis. Among Oligodendroglioma, Medulloblastoma & High Grade Glioma out of 63 patients 58 were found to be concordant [11C]-MET & [18F]-FDG scans. On semi-quantitative analysis mean T/ NT ratio was found to be 2.86 ± 0.91 for lesions positive for recurrence of tumors & 1.14 ± 0.82 for lesions negative for recurrence of tumor on [11C]-MET scan. While the ratio for [18F]-FDG scan on semi-quantitative analysis was found to be 2.05 ± 1.04 for lesions positive for recurrence of tumors & 0.52 ± 0.15 for lesions negative for recurrence of tumors.
Conclusions: The study highlight that [11C]-MET is superior to [18F]-FDG PET scans to detect recurrence in low grade glioma. A cut off value of target to non target value of 1.52 is a useful parameter to distinguish benign from malignant lesion on a [11C]-MET Scan. Both [18F]-FDG & [11C]-MET scan were found to be useful in High Grade Astrocytoma, Oligodendroglioma & Medulloblastoma.