RT Journal Article SR Electronic T1 Diagnostic Accuracy of 11C-Methionine PET for Differentiation of Recurrent Brain Tumors from Radiation Necrosis After Radiotherapy JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 694 OP 699 DO 10.2967/jnumed.107.048082 VO 49 IS 5 A1 Yuzo Terakawa A1 Naohiro Tsuyuguchi A1 Yoshiyasu Iwai A1 Kazuhiro Yamanaka A1 Shigeaki Higashiyama A1 Toshihiro Takami A1 Kenji Ohata YR 2008 UL http://jnm.snmjournals.org/content/49/5/694.abstract AB We evaluated the diagnostic accuracy of PET with l-methyl-11C-methionine (11C-MET) for the differentiation of recurrent brain tumors from radiation necrosis. Methods: Seventy-seven patients who had been previously treated with radiotherapy after primary treatment for metastatic brain tumor (n = 51) or glioma (n = 26) were studied to clarify the diagnostic performance of 11C-MET PET in differentiating between recurrent brain tumors and radiation necrosis. A total of 88 PET scans with 11C-MET were obtained; sometimes more than one scan was obtained when there was an indication of recurrent brain tumor or radiation necrosis. A definitive diagnosis was made on the basis of pathologic examination for recurrent brain tumors and on the basis of pathologic examination or clinical course for radiation necrosis. Several indices characterizing the lesions were determined; these included mean and maximum standardized uptake values (SUVmean and SUVmax, respectively) and the ratios of lesion uptake to contralateral normal frontal-lobe gray matter uptake corresponding to the SUVmean and the SUVmax (L/Nmean and L/Nmax, respectively). Receiver-operating-characteristic (ROC) curve analysis was used to determine the optimal index of 11C-MET PET and cutoff values for the differential diagnosis of tumor recurrence and radiation necrosis. Results: The values of each index of 11C-MET PET tended to be higher for tumor recurrence than for radiation necrosis. There were significant differences between tumor recurrence and radiation necrosis in all of the indices except for the L/Nmax for glioma. ROC analysis indicated that the L/Nmean was the most informative index for differentiating between tumor recurrence and radiation necrosis. An L/Nmean of greater than 1.41 provided the best sensitivity and specificity for metastatic brain tumor (79% and 75%, respectively), and an L/Nmean of greater than 1.58 provided the best sensitivity and specificity for glioma (75% and 75%, respectively). Conclusion: 11C-MET PET can provide quantitative values to aid in the differentiation of tumor recurrence from radiation necrosis, although these values do not appear to be absolute indicators. Quantitative analysis of 11C-MET PET data may be helpful in managing irradiated brain tumors.