The role of neuroimaging in neurotoxicity after chimeric antigen receptor T-cell therapy

Chimeric antigen receptor T-cell (CAR-T) therapy has become an established treatment for several haematological malignancies in relapse and is being evaluated for new indications. An important clinical challenge associated with the use of CAR-T therapy, however, is the common development of neurotoxicity. Different neurotoxicity syndromes have been reported. The best-known form of CAR-T neurotoxicity is immune effector cell-associated neurotoxicity syndrome, which can be associated with various findings on magnetic resonance imaging (MRI), including cerebral oedema and leptomeningeal enhancement. Other manifestations of neurotoxicity include movement disorders, myelopathy, cranial nerve palsies and ischaemic strokes. MRI plays a key role in the diagnosis and management of patients with suspected neurotoxicity. It can be used to support the diagnosis, exclude differential diagnoses and forms part of the grading of neurotoxicity. Other roles for MRI after CAR-T therapy include assessment of potential longer-term effects of therapy and neurotoxicity, and the evaluation of patients with emerging indications for CAR-T therapy. We recommend performing a baseline MRI brain prior to CAR-T therapy where feasible, as this greatly aids in the interpretation of neuroimaging findings. Here, we discuss the established and potential roles of neuroimaging in the context of neurotoxicity secondary to CAR-T therapy.