Usability of 11C-methionine positron emission tomography for differentiation of intracranial brain tumor from non-neoplastic lesions before treatment

We investigated the usability of 11C-methionine positron emission tomography (11C-METPET) for the differentiation of intracranial brain tumors from non-neoplastic lesions before treatment. Among 425 consecutive patients who underwent 11C-METPET imaging, 113 pretreatment patients were analyzed. Quantitative data including mean, peak, and maximum standardized uptake values and the ratios of lesion uptake to mean and maximum contralateral normal frontal lobe gray matter uptake (Lmax/Nmean and Lmax/Nmax), were analyzed. Next, the optimal cut-off for the differential diagnosis of brain tumors from non-neoplastic lesions were determined using receiver-operating characteristics curves. Finally, positive and negative predictive value were calculated. The final diagnoses for brain tumors included central nervous system tumor, lymphoma, and metastatic brain tumor, whereas the non-neoplastic lesions included neurovascular disease, dysplasia, encephalopathy, and inflammatory disease. An Lmax/Nmax of greater than 2.01 and an Lmax/Nmean of greater than 2.23 provided the best sensitivity and specificity for the differential diagnosis of brain tumor. However, the positive and negative predictive value were 96.5% and 47.4%, respectively, for Lmax/Nmax, and 93.7% and 50%, respectively, for Lmax/Nmean. Considering high positive predictive value and low negative predictive value in relation to the diagnosis based on the optimal cut-off, the utilization of 11C-METPET imaging before treatment requires careful attention.