Continuous and differential improvement in worldwide access to hematopoietic cell transplantation: activity has doubled in a decade with a notable increase in unrelated and non-identical related donors

Abstract

Promoting access to and excellence in hematopoietic cell transplantation (HCT) by collecting and disseminating data on global HCT activities is one of the principal activities of the Worldwide Network for Blood and Marrow Transplantation, a non-governmental organization in working relations with the World Health Organization. HCT activities are recorded annually by member societies, national registries and individual centers including indication, donor type (allogeneic/autologous), donor match and stem cell source (bone marrow/peripheral blood stem cells/cord blood). In 2018, 1,768 HCT teams in 89 countries (6 World Health Organization regions) reported 93,105 (48,680 autologous and 44,425 allogeneic) HCT. Major indications were plasma cell disorders and lymphoma for autologous, and acute leukemias and MDS/MPN for allogeneic HCT. HCT numbers increased from 48,709 in 2007. Notable increases were seen for autoimmune diseases in autologous and hemoglobinopathies in allogeneic HCT. The number of allogeneic HCT more than doubled with significant changes in donor match. While HCT from HLA-identical siblings has seen only limited growth, HCT from non-identical related donors showed significant increase worldwide. Strongest correlation between economic growth indicator of gross national income/capita and HCT activity/10 million population was observed for autologous HCT (correlation coefficient [r]=0.79). HCT from unrelated donors showed strong correlation (r=0.68), but only moderate correlation was detected from related donors (r=0.48 for HLA-identical sibling; r=0.45 for other). The use of HCT doubled in about a decade worldwide at different speed and with significant changes regarding donor match as a sign of improved access to HCT worldwide. Although narrowing, significant gaps remain between developing and non-developing countries.

Figure 1.

Hematopoietic cell transplantation (HCT) activity per 10,000,000 population (i.e., transplant rate) for human leukocyte antigen-identical sibling HCT, other related HCT, HCT from unrelated donors, and unrelated cord blood transplantation in 2018. The numbers of countries with more than 25 (or more than 50) transplant rate (TR) for human Leukocyte antigen (HLA)-identical sibling hematopoietic cell transplantation (HCT) (A), other related HCT (B), HCT from unrelated donors (C), and unrelated cord blood transplantation (CBT) (D) were 45(25), 26(8), 37(33), and 2(1), respectively.

Figure 2.

Correlation between economic indicators and hematopoietic cell transplantation activity. Correlations between economic indicator of gross national income (GNI) per capita and autologous (A) and allogeneic (B) hematopoietic cell transplantation (HCT) activity per 100,000 population were observed (correlation coefficient [r]=0.79, and 0.66 for autologous and allogeneic, respectively). Among allogeneic HCT, HCT from human leukocyte antigen (HLA)-identical sibling donors (C) (r=0.48) and HCT from other related donors (D) (r=0.45) showed moderate correlation, and HCT from unrelated donors showed strong correlation (E) (r=0.68). EUR: European region: EMR: Eastern Mediterranean region; AFR: African region; SEAR: South-East Asian region; WPR: Western Pacific region; AMR: region of Americas.

Figure 3.

Trend of the numbers of allogeneic hematopoietic cell transplantation from human leukocyte antigen-identical sibling donors, other related donors, or unrelated donors by World health Organization regions. (A) Allogeneic hematopoietic cell transplantation (HCT) from human leukocyte antigen (HLA)-identical siblings has seen limited growth from 2007 to 2018. (B) HCT from other related donors increased from 2007 to 2018 in all regions. (C) Trend of HCT from unrelated donors differed among regions. (D) The global trend of unrelated cord blood transplantation showed decrease since 2011 in all regions except South-East Asian region and Western Pacific region (SEAR/WPR).

Figure 4.

Trend of disease stage at transplant for acute myeloid leukemia, acute lymphoblastic leukemia, and chronic myeloid leukemia. (A) The proportion of non-first complete remission (CR1) is decreased by approximately 10% globally as a sign that acute myeloid leukemia (AML) are transplanted earlier in their disease stage. (B) Similar applies to acute lymphoblastic leukemia (ALL), although the amount of decrease in the proportion of non-CR1 is approximately 5%. (C) Trends in the proportion of >1^st chronic phase (>1CP) in overall chronic myeloid leukemia (CML) is approaching 80% in region of Americas (AMR), North and South-East Asian region and Western Pacific region (SEAR/WPR), followed by 50-60% in other regions.