Among patients who receive either peripheral blood stem cells (PBMCs) or bone marrow from unrelated donors, the incidence of overall chronic graft-versus-host-disease (GVHD; 53%) is higher in those who received PBMCs than in those who received bone marrow stem cells (40%). Both transplant sources had the same risks for overall survival, relapse, non-relapse mortality, and acute GVHD; however, the patients who received PBMCs did have faster engraftment.

Approximately one third of all patients who need a PBMC or bone marrow transplant to treat leukemia or another blood disease are able to secure a related donor. For the 70% who cannot find a donor within their family, most will find an unrelated donor. Most transplant centers are increasingly using PBMCs as a source for adult stem cells because of their superiority in clinical trials that directly compared PBMCs and bone marrow from related donors. However, this is the first comparative study of the two transplant sources that has prospectively analyzed patient outcomes in unrelated donor transplants, which are a majority of transplants.

This phase III study randomized 278 patients to receive bone marrow and 273 to receive PBMCs as the graft source for transplant. The study involved 47 research sites over 2 years, and the goal was to compare the 2-year survival probabilities for patients transplanted with PBMCs or bone marrow stem cells from unrelated donors so that the effects of graft source on outcome could be determined.

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In addition to the higher incidence of chronic GVHD, those patients who received a PBMC transplant from an unrelated donor also had a higher incidence of GVHD affecting multiple organs (46%) than did those who received bone marrow stem cells (31%).

In an accompanying editorial, Fred Appelbaum, MD, director of Clinical Research at Fred Hutchinson Cancer Research Center, asserted that bone marrow, and not PBMCs, should be the source for unrelated donor adult stem cells for most patients who require a transplant.

“For the majority of unrelated transplants following a standard high-dose preparative regimen, bone marrow should be used since survival is equivalent with the two sources but the incidence of chronic graft-versus-host disease, which can be a debilitating complication, is significantly less with marrow,” Appelbaum wrote.

He added, “While this study should change practice, it will be interesting to see if it really does. The benefits of peripheral blood are seen early, under the watchful eyes of the transplant physician, while the deleterious effects occur late, often after the patient has left the transplant center.”

This study was published in the New England Journal of Medicine (2012;367:1487-1496, with the accompanying editorial at 367:1555-1556).