Stem cell boost for immune effector cell associated hematotoxicity in multiple myeloma: minimizing long-term complications and expanding post CAR T-cell therapy relapse options

Introduction Cytopenia is one of the most common adverse events after BCMA chimeric antigen receptor (CAR) T cell therapy in the treatment of relapsed multiple myeloma (MM). The term Immune Effector Cell Associated Hematotoxicity (ICAHT) was coined to describe the unique hematological toxicities following novel CAR T cell therapies. The management of prolonged ICAHT ( > 30 days) is quite challenging, and patients have high incidences of infections, require prolonged transfusion support and have an increased non-relapse mortality. Stem cell boost (SCB) leads to prompt and durable count recovery and can minimize long-term complications while enabling therapeutic options in the post CAR T-cell therapy relapse setting.