Abstract
1683
Background: C-11Methionine positron emission tomography has reported to be useful to distinguish brain tumor recurrence from radiation necrosis. We undertook this study to directly compare F-18 flurodeoxyglucose (FDG) PET and C-11 methionine (MET) PET for the evaluation of recurrence in brain tumors.MethodThirty-seven patients with a history of treated brain tumors (31 primary brain tumor and 6 metastatic tumor) referred for evaluation of recurrent disease were initially included in the study. There were 22 males and 15 females (mean age: 38.7 ± 14.4 years; range: 15 to 65 years). All patients underwent the MET and FDG study within 2 weeks. Visual image interpretation was performed independently by 2 PET physicians for each tracer using the fused PET/CT images. Images were analyzed semiquantitatively using tumor to normal contralateral cortex ratios (T/N). Imaging results were compared with histopathology on tumor excision or biopsy in 10 patients and with clinical follow-up in 27 patients.
Results: The final diagnosis was tumor recurrence in 27 patients and no recurrence/stable disease in 10 patients. On FDG, findings in 23/37 (62.2%) were suggestive of recurrent tumors. On MET, findings in 28/37 (75.7%) cases were suggestive of recurrent tumors. Spatially separated secondary lesions were clearly delineated in 4 cases, 3 were glioblastoma multiforme (GBM) and 1 were anaplastic astrocytoma. Two of the secondary lesions were missed on FDG PET. Using a cutoff for T/N ratio on FDG of >0.90 to differentiate recurrence from no recurrence, sensitivity of FDG was 74.1%, whereas specificity was 70.0%. Area under the curve was 0.86. Using a cutoff for T/N ratio of >2.1 to differentiate recurrence from no recurrence, sensitivity of MET was 92.6%, whereas specificity was 80.0%. Area under the curve was 0.95.ConclusionSemiquantitative analysis of MET can provide more informative values than FDG to aid in the differentiation of tumor recurrence from radiation necrosis.