“…A challenging issue for clinicians is the assessment of tumor response after radiation due to overlapping tumor progression and treatment-related changes. As reviewed in the present issue, MRS, PWI, and PET might assist in the differential diagnosis between pseudo-progression and true progression [6,7], providing relevant data for informed treatment decisions. In this context, the contribution of amino acid PET might be of high value [12,13], strengthening evidence for a change in treatment when the results of advanced MRI techniques are not conclusive.…”