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 nonmalignant disorders. In the past two decades, peripheral blood stem cells replaced bone marrow as stem cell source due to faster engraftment and practicability. Previous meta-analyses analysed patients treated from 1990 to 2002 and demonstrated no impact of the stem cell source on overall survival, but a greater risk for graft-versus-host disease (GvHD) in peripheral blood transplants. As transplant indications and conditioning regimens continue to change, whether the choice of the stem cell source has an impact on transplant outcomes remains to be determined. Objectives To assess the effect of bone marrow versus peripheral blood stem cell transplantation in adult patients with haematological malignancies with regard to overall survival, incidence of relapse and non-relapsemortality, disease-free survival, transplant-relatedmortality, incidence of GvHD and time to engraftment. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 1), MEDLINE (from 1948 to February 2014), trial registries and conference proceedings. The search was conducted in October 2011 and was last updated in February 2014. We did not apply any language restrictions. Selection criteria We included randomised controlled trials (RCTs) comparing bone marrow and peripheral blood allogeneic stem cell transplantation in adults with haematological malignancies. Data collection and analysis Two review authors screened abstracts and extracted and analysed data independently. We contacted study authors for additional information. We used the standard methodological procedures expected by The Cochrane Collaboration. Main results We included nine RCTs that met the pre-defined selection criteria, involving a total of 1521 participants. Quality of data reporting was heterogeneous among the studies. Overall, the risk of bias in the included studies was low. For the primary outcome overall survival, our analysis demonstrated comparable results between bone marrow transplantation (BMT) and peripheral blood stem cell transplantation (PBSCT) (six studies, 1330 participants; hazard ratio (HR) 1.07; 95% CI 0.91 to 1.25; P value = 0.43; high-quality evidence). Disease-free survival (six studies, 1225 participants; HR 1.04; 95% CI 0.89 to 1.21; P value = 0.6; moderate-quality of evidence) and non-relapse or transplant-related mortality (three studies, 758 participants; HR 0.98; 95% CI 0.76 to 1.28; P = 0.91; high-quality evidence) were also comparable between transplantation arms. In the related-donor setting, data from two of eight studies with 211 participants (21%) indicated a higher relapse incidence in participants transplanted with bone marrow stem cells rather than peripheral blood stem cells (HR 2.73; 95% CI 1.47 to 5.08; P value = 0.001). There was no clear evidence of a difference in relapse incidence between transplantation groups in unrelated donors (HR 1.07; 95% CI 0.78 to 1.47; P value = 0.66). The difference between the donor-related and -unrelated subgroups (P-value = 0.008) was considered to be statistically significant. BMT was associated with lower rates of overall and extensive chronic GvHD than PBSCT (overall chronic GvHD: four studies, 1121 participants; HR 0.72; 95% CI 0.61 to 0.85; P value = 0.0001, extensive chronic GvHD: four studies, 765 participants; HR 0.69; 95% CI 0.54 to 0.9; P value = 0.006; moderate-quality evidence for both outcomes). The incidence of acute GvHD grades II to IV was not lower (six studies, 1330 participants; HR 1.03; 95% CI 0.89 to 1.21; P value = 0.67; moderate-quality evidence), but there was a trend for a lower incidence of grades III and IV acute GvHD with BMT than with PBSCT (three studies, 925 participants; HR 0.75; 95% CI 0.55 to 1.02; P value = 0.07; moderate-quality evidence). Times to neutrophil and platelet engraftment were longer with BMT than with PBSCT (neutrophil: five studies, 662 participants; HR 1.96; 95% CI 1.64 to 2.35; P value < 0.00001; platelet: four studies, 333 participants; HR 2.17; 95% CI 1.69 to 2.78; P value < 0.00001). Authors' conclusions This systematic review found high-quality evidence that overall survival following allo-HSCT using the current clinical standard stem cell source - peripheral blood stem cells - was similar to that following allo-HSCT using bone marrow stem cells in adults with haematological malignancies. We found moderate-quality evidence that PBSCT was associated with faster engraftment of neutrophils and platelets, but a higher risk of GvHD (in terms of more overall and extensive chronic GvHD). There was an imprecise effect on relapse and on severe (grades III to IV) acute GvHD. Quality of life, which is severely affected by GvHD, was not evaluated. Against the background of transplantation practices that have clearly changed over the past 10 to 15 years, our aim was to provide current data on the best stem cell source for allo-HSCT, by including the results of recently conducted trials. Our review includes participants recruited up to 2009, a proportion of whom were older, had received reduced-intensity conditioning regimens or had been transplanted with stem cells from unrelated donors. However, only one, large, study included relatively recently treated participants. Nevertheless, our findings are comparable to those of previous meta-analyses suggesting that our results hold true for today's practice.