In a retrospective study reported in a research letter in Blood Advances, Rejeski et al found that a stem cell boost was successful in treating severe hematologic toxicity in patients who had received CD19 chimeric antigen receptor (CAR) T-cell therapy for refractory B-cell malignancies.
Study Details
The study included 12 patients with severe hematologic toxicity after CAR T-cell treatment from European centers; the patients received stem cell boosts between April 2019 and March 2022. The toxicity profile between CAR T-cell therapy and stem cell boost was characterized by prolonged severe neutropenia and thrombocytopenia (median duration = 42 days) and severe infections (58% of patients). The stem cell source was an autologous product in nine patients, with three receiving stem cells from a previous allogeneic donor with no subsequent evidence of graft-vs-host disease. Two patients received more than one boost.
Our study indicates that stem cell boost represents a clinically feasible strategy for persistent cytopenia after CD19 CAR T [-cell therapy] with high engraftment rates, resolution of cytopenia in most cases, and encouraging survival outcomes.— Rejeski et al
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Key Findings
The median time to stem cell boost from CAR T-cell treatment was 69 days (range = 35–617 days). On the day of stem cell transplantation, median absolute neutrophil count was 0.5/µL (range = 0–7.9/µL), and median platelet count was 27/µL (range = 2–133/µL). The indication for boost was severe pancytopenia in six patients, and persistent neutropenia or thrombocytopenia in six patients.
Neutrophil engraftment occurred in all patients, with a 30-day cumulative engraftment rate of 82%. Median time to engraftment was 15 days (range = 6–124 days). Platelet engraftment occurred in seven of nine patients, with one patient engrafting after a second autologous stem cell boost. Median time to engraftment was 21 days (range = 12–34 days), with a 30-day engraftment rate of 60%.
Progression-free survival and overall survival rates at 1 year were 46% and 55%, respectively. Median progression-free survival was 6 months, and median overall survival was 17 months. Nonrelapse mortality at 1 year was 8% (one death due to infection).
The investigators concluded: “Our study indicates that stem cell boost represents a clinically feasible strategy for persistent cytopenia after CD19 CAR T-cell therapy with high engraftment rates, resolution of cytopenia in most cases, and encouraging survival outcomes.”
Marion Subklewe, MD, of the Department of Medicine III–Hematology/Oncology, University Hospital, LMU Munich, is the corresponding author of the Blood Advances article.
Disclosure: The study was supported by the Else Kröner Forschungskolleg, German Research Foundation, and others. For full disclosures of the study authors, visit ashpublications.org/bloodadvances.
