CAR-T cell therapy is a revolutionary immunotherapy that uses genetically modified white blood cells to fight cancer cells.[1] According to a retrospective study, immune-related adverse events (CirAEs) associated with this therapy in patients with multiple myeloma were associated with a high rate of non-relapse mortality. These are complications that arise as a side effect of treatment when the immune system is over-activated. Researchers have found that levels of a protein called neurofilament light chain (NfL) are higher in patients who have neurotoxic problems after CAR-T cell therapy.[2] High amounts of this protein are present before therapy begins and remain high during and up to a month after treatment. These findings suggest that measuring NfL levels in blood samples could help healthcare professionals predict potentially fatal complications of therapy. The study thus points to the need for better monitoring and management of immune side effects in CAR-T therapy in myeloma patients.