Local Cytokine Release Syndrome After Idecabtagene Vicleucel Therapy in Patients With Multiple Myeloma: Two Case Reports.

Chimeric antigen receptor T-cell (CAR-T) therapy targeting the B-cell maturation antigen (BCMA) is an effective treatment for patients with relapsed/refractory multiple myeloma (RRMM). However, cytokine release syndrome (CRS) represents a significant complication associated with CAR-T therapy. While most CRS cases involve systemic symptoms such as fever, hypotension, and respiratory distress, localized symptoms (referred to as local CRS) can also occur. Herein, we report two cases of local CRS without cervical lesions that occurred at our institution. Both patients had triple-class refractory RRMM prior to therapy. Following idecabtagene vicleucel (ide-cel) administration, both developed grade 1 CRS on the day of ide-cel administration; one case improved with tocilizumab, while the other improved with tocilizumab and dexamethasone (dex). However, on the third day post-administration, they exhibited symptoms characterized by neck swelling, leading to a risk of airway obstruction. Both cases were diagnosed as local CRS, and prompt dex administration resulted in rapid symptom improvement. These cases underscore the importance of monitoring for local CRS even in the absence of "cervical myeloma lesions", particularly during the early phase following ide-cel administration. Early administration of dex is crucial for the effective management of local CRS.