The value of 11C-methionine PET in the early differentiation between tumor recurrence and radionecrosis in patients treated for a high-grade glioma and indeterminate MRI

Abstract

ObjectiveTo evaluate the contribution of 11C-Methionine PET in the early differentiation between tumor recurrence and radionecrosis in patients treated for a high grade glioma. MethodThe study included 30 patients with glioma (III/IV grade) treated with surgery/radiotherapy/chemotherapy (5–8 months) and with an indeterminate MRI.All patients underwent a 11C-Methione PET (within 15 days of MRI) and studies were visually analyzed (intensity and morphology of uptake), quantified (SUV max/SUV mean background), and coregistered to MRI (3D-Flair).Patient management was decided by the neuro-oncology committee to clinical and imaging follow-up, second-line treatment, or surgery. ResultsThere were 23 11C-Methionine PET studies visually positive. Morphology of uptake was focal in 15, diffuse in 4, and ring-shaped in 4.Three out of the focal uptake cases underwent resection (Histopathology +). Sixteen underwent second-line therapy (11 responded; 5 progressed). The 4 cases with ring-shaped uptake were followed-up, and progression was found in 2 (true-positive), and disease-free in 2 (follow-up of 6 and 7 months, respectively) (false-positive).Seven out of 11C-Methionine PET studies were visually negative, and all of them were disease-free (follow-up of 3–12 months).SUV lesion/background was 2.79±1.35 in tumor recurrence, and 1.53±0.39 in radionecrosis (P<.05).Taking into account a SUV lesion/background threshold of 2.35, the sensitivity and specificity values were 90.5% and 100%, respectively. ConclusionVisual analysis, quantitative and PET/MRI coregistration of 11C-Methionine PET showed their complementary role in patients with indeterminate MRI results, thus allowing early differentiation between tumor recurrence and radionecrosis, and helping in the individual therapy approach.