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.

Areas covered: Herein we review current data on ICAHT, determine how SCB can lead to improved outcomes, and offer a view on future applications of SCB. The database 'pubmed' was searched for the terms 'CAR-T,' 'ICAHT', and 'Stem Cell', and results as well as selected citations were used for the present study.

Expert opinion: SCB for prolonged ICAHT improves morbidity and potentially mortality. Future use of SCB will depend on the long-term outcomes of CAR-T cell therapy in earlier treatment lines. For patients with high likelihood of ICAHT, prophylactive stem cell collection should be considered.