Therapy Response Imaging in Central Nervous System (CNS) Malignancy

The wide spectrum of central nervous system (CNS) neoplasms and treatment-related changes makes imaging evaluation of treatment response challenging. In this chapter, we provide an overview of disease-specific approaches for therapy-response imaging. First, we review relevant background, such as classic MRI characteristics of pre- and posttreatment changes in CNS malignancy, the WHO brain tumor classification, and novel therapeutic approaches for CNS malignancy. Next, we discuss CNS therapy-response imaging strategies and pitfalls, including a discussion of RANO, pseudoprogression, pseudoresponse, and radiation necrosis. Lastly, we review emerging approaches for CNS therapy-response imaging, such as iRANO and radiomics. Understanding posttreatment imaging changes of CNS malignancies is crucial to help direct clinical management.