The combination of [18F]-CFA PET and advanced MRI can help distinguish tumor progression from inflammation in patients with GBM treated with DC vaccination and PD-1 mAb blockade. Postcontrast T1-weighted, T1-subtraction, relative CBV, ADC, [18F]-FAC PET + MRI fusion, and whole-body maximum-intensity projection images of [18F]-CFA from two patients (A, patient A; B, patient B) with recurrent GBM before (Top) and after (Bottom) immunotherapy.