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

Objective: To evaluate the contribution of(11)C-Methionine PET in the early differentiation between tumour recurrence and radionecrosis in patients treated for a high grade glioma. Method: The 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 C-11-Methione PET (within 15 days of MRI) and studies were visually analysed (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. Results: There were 23 C-11-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(11)C-Methionine studies PET were visually negative, and all of them were disease-free (followup of 3-12 months). SUV lesion/background was 2.79 +/- 1.35 in tumour 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. Conclusion: Visual analysis, quantitative and PET/MRI coregistration of C-11-Methionine PET showed their complementary role in patients with indeterminate MRI results, thus allowing early differentiation between tumour recurrence and radionecrosis, and helping in the individual therapy approach. (C) 2016 Elsevier Espana, S.L.U. y SEMNIM. All rights reserved.