Neuroimaging of Brain Tumors: Pseudoprogression, Pseudoresponse, and Delayed Effects of Chemotherapy and Radiation

Management of patients with brain cancer critically depends on an accurate interpretation of imaging findings that will guide treatment decisions. Treatment with chemotherapy and radiation can affect the imaging characteristics of a tumor and therefore cause misinterpretation of treatment response. Specifically, radiotherapy or chemotherapy may result in distinctive imaging abnormalities that can be challenging to differentiate from tumor itself. Moreover, cancer therapy can be associated with unique adverse effects on the brain, which need to be appropriately recognized by the treating physician to guide patient management. Specific imaging findings, such as radiation-induced tissue necrosis, leukoencephalopathy, pseudoprogression, and pseudoresponse represent treatment-related phenomena that can complicate interpretation of imaging studies and clinical decision making. The aim of this review is to describe these phenomena and improve clinician familiarity as to how these appear on structural (MRI) and functional (perfusion, spectroscopy, PET) imaging studies.