Bone marrow versus peripheral blood allogeneic haematopoietic stem cell transplantation for haematological malignancies in adults.

Background: Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is an established treatment option for many malignant and non-malignant haematological disorders. Peripheral blood stem cells represent the main stem cell source in malignant diseases due to faster engraftment and practicability issues compared with bone marrow stem cells. Since the early 2000s, there have been many developments in the clinical field. Allo-HSCT using haploidentical family donors (haplo-HSCT) has emerged as an alternative for people who do not have human leukocyte antigen (HLA)-matched siblings or unrelated donors. In addition, the introduction of new methods and strategies in allo-HSCT, such as the use of post-transplant cyclophosphamide (PT-Cy), better donor selection, the more frequent administration of anti-thymocyte globulins (ATGs), but also improved management of side effects such as graft-versus-host disease (GvHD) and infection, have impacted outcomes after allo-HSCT. In addition, as transplant indications and strategies continue to adapt in line with novel research findings, the effect of the stem cell source on post-transplant outcomes is unclear. For our analysis, we considered peripheral blood stem cells as the standard graft source for adults with haematological malignancies. This is an update of a review first published in 2014.

Objectives: To assess the effect of bone marrow transplantation versus peripheral blood stem cell transplantation in adults with haematological malignancies with regard to overall survival, disease-free survival, incidence of non-relapse or transplant-related mortality, incidence of extensive chronic graft-versus-host disease (GvHD), incidence of acute GvHD grades III to IV, incidence of overall chronic GvHD, and quality of life.

Search methods: For this update we searched CENTRAL, MEDLINE, Embase, and two trials registries on 2 November 2022 with no language restrictions.

Selection criteria: We included randomised controlled trials (RCTs) comparing bone marrow transplantation (BMT) with peripheral blood stem cell transplantation (PBSCT) in adults (aged ≥ 18 years) with haematological malignancies.

Data collection and analysis: Two review authors independently selected studies and extracted data. We evaluated risk of bias using the original Cochrane risk of bias tool (RoB 1), and we evaluated the certainty of the evidence using the GRADE approach.

Main results: The updated search identified no new studies for inclusion. We found two additional reports relating to a previously included study; they provided new data on quality of life and infection rates after transplantation. As these are clinically relevant outcomes, quality of life was added to the summary of findings table (replacing acute GvHD II to IV), and rate of infection was added to our list of secondary outcomes. We included nine RCTs with a total of 1521 participants. Overall, the risk of bias in the included studies was low. Median participant age across studies ranged from 21 to 45 years, and studies took place in Canada, the USA, New Zealand, Brazil, Australia, Egypt, and across Europe. Bone marrow transplantation (BMT) compared with peripheral blood stem cell transplantation (PBSCT) likely results in little to no difference in overall survival (hazard ratio (HR) for all-cause death 1.07, 95% CI 0.91 to 1.25; 6 studies, 1330 participants; moderate-certainty evidence). There may be little to no difference between BMT and PBSCT in terms of disease-free survival (HR for disease recurrence or all-cause death 1.04, 95% CI 0.89 to 1.21; 6 studies, 1225 participants; low-certainty evidence) and non-relapse or transplant-related mortality (HR 0.98, 95% CI 0.76 to 1.28; 3 studies, 758 participants; low-certainty evidence). BMT compared with PBSCT likely results in lower rates of extensive chronic GvHD (HR 0.69, 95% CI 0.54 to 0.90; 4 studies, 765 participants; moderate-certainty evidence) and overall chronic GvHD (HR 0.72, 95% CI 0.61 to 0.85; 4 studies, 1121 participants; moderate-certainty evidence). BMT compared with PBSCT may reduce the incidence of acute GvHD grades III to IV, although the 95% CI of the HR is also compatible with no effect (HR 0.75, 95% CI 0.55 to 1.02; 3 studies, 925 participants; moderate-certainty evidence). Evidence from two trials that used different quality of life assessment instruments suggests that BMT compared with PBSCT may be associated with higher quality of life five years after transplantation.

Authors' conclusions: Moderate-certainty evidence suggests little to no difference in overall survival following allo-HSCT using bone marrow versus peripheral blood stem cells (the current clinical standard stem cell source). Low-certainty evidence suggests little to no difference between the stem cell sources in terms of disease-free survival and non-relapse or transplant-related survival. BMT likely reduces the risk of extensive chronic GvHD and overall chronic GvHD compared with PBSCT. Evidence from two RCTs suggests that BMT compared with PBSCT may result in higher long-term quality of life, possibly due to the lower chronic GvHD incidence. With this update, we aimed to supply the most recent data on the choice of stem cell source for allo-HSCT in adults by including new evidence published up to November 2022. We identified no new ongoing studies and no new RCTs with published results. Further research in this field is warranted.