An Analysis of the Worldwide Utilization of Hematopoietic Stem Cell Transplantation for Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) has an aggressive course and a historically dismal prognosis. For many patients, hematopoietic stem cell transplantation (HSCT) represents the best option for cure, but access, utilization and health inequities on a global scale remain poorly elucidated. Objective: To describe patterns of global HSCT use in AML for a better understanding of global access, practices, and unmet needs internationally. Study design: Estimates of AML incident cases in 2016 were obtained from the Global Burden of Disease (GBD) 2019 study. HSCT activities were collected from 2009-2016 by the Worldwide Network for Blood and Marrow Transplantation (WBMT) through its member organizations. The primary endpoint was global and regional use (number of HSCT) and utilization of HSCT (number of HSCT/ number of incident cases) for AML. Secondary outcomes included trends from 2009 to 2016 in donor type, stem cell source and remission status at time of HSCT. Results: Global AML incidence has steadily increased, from 102,000 (95% uncertainty interval (UI): 90,200-108,000) in 2009 to 118,000 (104,000-126,000) in 2016 (+16.2%). Over the same period, a +54.9% increase from 9,659 to 14,965 HSCT/year was observed globally, driven by an increase in allogeneic (+64.9%) with a reduction in autologous (-34.9%) HSCT. While the highest numbers of HSCT continue to be performed in high-resource regions, the largest increases were seen in resource-constrained regions [+94.6% in Africa/East Mediterranean Region (AFR/EMR); +34.7% in America-Nord Region (AMR-N)]. HSCT utilization was skewed towards high-resource regions [in 2016: AMR-N 18.4%, Europe (EUR) 17.9%, South-East Asia/Western Pacific Region (SEAR/WPR) 11.7%, America-South Region (AMR-S) 4.5% and AFR/EMR 2.8%]. For patients <70 years of age, this difference in utilization was widened; AMR-N had the highest allogeneic utilization rate, increasing from 2009 to 2016 (30.6% to 39.9%) with continued low utilization observed in AFR/EMR (1.7% to 2.9%) and AMR-S (3.5% to 5.4%). Across all regions, total HSCT for AML in 1st complete remission (CR1) increased (from 44.1% to 59.0%). Patterns of donor stem cell source from related versus unrelated donors varied widely by geographic region. SEAR/WPR had a +130.2% increase in related donor from 2009 to 2016 and >95% HSCT donors in AFR/EMR were from related; in comparison, AMR-N and EUR have a predilection for unrelated HSCT. Globally, allogeneic HSCT stem cell source was predominantly peripheral blood (69.7% of total HSCT in 2009 increased to 78.6% in 2016). Autologous HSCT decreased in all regions from 2009 to 2016 except in SEAR/WPR (+18.9%). Conclusions: HSCT remains a central curative treatment modality in AML. Allogeneic HSCT for AML is rising globally but there are marked variations in regional utilization and practices, including types of graft source. Resource-constrained regions have the largest growth in HSCT use, but utilization rates remain low with a predilection for familial related donor sources and are typically offered in CR1. Further studies are necessary to elucidate the reasons, including economic factors, to understand and address these health inequalities and improve discrepancies in use of HSCT as a potentially curative treatment globally.