The value of 11C-methionine PET/CT in diagnosis and treatment of brain stem glioma

Objective To explore the value of 11C-methionine (MET)-PET/CT in grading brain stem glioma (BSG) and guiding its microsurgical resection. Methods A prospective study population comprised 63 patients who underwent MRI scans demonstrating suspicious BSG at Neurosurgery Department of Beijing Tiantan Hospital, Capital Medical University from January 2015 to December 2016. Among them, 20 patients only received stereotactic biopsy and MET-PET/CT scanning. The remaining 43 patients included 22 who underwent tumor resection under multi-modality guidance based on MET-PET/CT and 21 who received MR-guided resection. Semi-quantitative parameters including the maximal standardized uptake value (SUVmax), mean SUV (SUVmean), maximal tumor-to-background ratio (TBRmax), mean TBR (TBRmean) and total lesion methionine uptake (TLMU) obtained from presurgical MET-PET/CT images were compared between higher and lower tumor grading and their accuracy for indicating tumor grading. The ratio of high grade glioma resection was compared between 2 cohorts of patients. Results Out of all 63 patients, 37 had high grade gliomas and the other 26 patients had low grade gliomas. The SUVmax, SUVmean, TBRmax and TBRmean of high grade gliomas were higher than those of low grade gliomas (all P<0.01), while TLMU showed no significant difference between 2 cohorts (P=0.506). The accuracy for diagnosis of high grade glioma was 70.7% (29/41), 63.4% (26/41), 80.5% (33/41) and 73.2% (30/41), respectively, and the specificity was 91.7% (11/12). Multiple modality-guided group had larger ratio of high grade tumor resection than MRI-guided group (81.0% vs. 36.4%, P=0.005). Forty-three patients undergoing microsurgical resection were followed up for an average of 12.9 months (0.3-25.4 months), and the median survival time in multiple modality- and MRI-guided cohorts were 11.9 and 14.1 months, respectively (P=0.289). Conclusions MET-PET/CT parameters are associated with histological grade and demonstrate good accuracy and specificity for tumor grading diagnosis. Multi-modality guidance appears superior to MRI guidance for resection of high grade tumors. Key words: Brain stem neoplasms; Glioma; Positron-emission tomography; 11C-methionine