Current Activity Trends and Outcomes in Hematopoietic Cell Transplantation and Cellular Therapy - A Report from the CIBMTR.

The Center for International Blood and Marrow Transplant Research (CIBMTR) compiles annual summary slides describing trends in hematopoietic cell transplantation (HCT) and cellular therapy (CT) practice and outcomes. This year's report includes all patients receiving their first autologous and/or allogeneic HCT/CT in the United States between 2013 and 2023 or chimeric antigen receptor T-cell (CAR-T) therapy from 2016 and 2023, reported to the CIBMTR. A relative proportion of allogeneic and autologous HCT/CT was generated as percentage of total for donor type and for patient age, disease indication, graft-versus-host disease (GVHD) prophylaxis, and race and ethnicity. Causes of death were summarized using frequencies, and the Kaplan-Meier estimator was used for estimating overall survival. New for this year, disease risk stratification reflects the European LeukemiaNet cytogenetic risk score for acute myeloid leukemia (AML) and the Revised International Prognostic Scoring System for myelodysplastic syndromes (MDS). Use of allogeneic HCT increased substantially in 2023, recovering from a decline in activity during the COVID-19 pandemic, with growth predominately in the 65- to 74-year-old age group. Overall, matched unrelated donors (MUDs) continue to be the most common allogeneic donor source (45%) followed by haploidentical related donors (Haplo; 21%), matched related donors (MRDs; 18%), mismatched unrelated donors (MMUDs; (12%), and cord blood (Cord; 3%). These trends hold in the adult patient population, with a notable doubling of MMUD utilization since 2020 driven by the rapid shift to post-transplantation cyclophosphamide-based GVHD prophylaxis (PTCy) in this setting. In the pediatric setting, Haplo was the most common donor source, surpassing MRD use in 2023 followed by MUD, Cord, and MMUD use. Autologous HCT continued to decline slightly, whereas use of CAR-T therapy has rapidly increased since commercial approval in 2017, with lymphoma and multiple myeloma reaching 45% and 16%, respectively, in 2023. Significant recent changes in GVHD prophylaxis in the adult allogeneic HCT setting have occurred. PTCy is most common in Haplo HCT with >90% since 2016. Among other donor sources, the most rapid adoption is in MMUD HCT at 82% in 2023. In MRDs and MUDs, PTCy use differs by conditioning intensity, with non-myeloablative/reduced-intensity conditioning (NMA/RIC) higher (58% and 64%, respectively), reflecting the standard of care established by BMT CTN 1703, compared with myeloablative (MAC; 43% and 46%, respectively). In pediatrics, calcineurin inhibitor ± others remains the most common GVHD prevention strategy for use of MRDs (88%) and MUDs (68%). Although common in the pediatric Haplo HCT setting at 68% in 2023, use of PTCy is less common across other mismatched donor types in which use of abatacept or ex-vivo T-cell depletion/CD34 selection accounts for 28% and 17% in MMUDs, respectively. Three-year overall survival continues to significantly improve among patients receiving allogeneic (62.1% vs. 55.8%) and autologous (82.6% vs. 79.6%) HCT when comparing HCT from 2017 to 2022 versus 2012 to 2016 (P < .001), respectively. In both the adult and pediatric settings, primary cause of mortality after 100 days post-HCT remains primary disease in both allogeneic (47% and 45%, respectively) and autologous (60% and 79%, respectively). HCT/CT and CAR-T use continues to grow. Relapse remains the primary cause of death in the malignant setting, supporting further efforts to mitigate risk.