How does long-term survival compare among recipients of bone marrow transplants versus cord blood transplants?
Answer: They are comparable. Among pediatric patients, the overall survival rates are comparable for the two transplant types, but the causes of death differ with each. Among Cord Blood transplants, the most common cause of death was complications during the long wait for engraftment. Among bone marrow transplants, more patients died of severe Graft-Versus-Host Disease. Despite the FACT that Cord Blood seems to lack graft-versus-tumor activity, Cord Blood transplants were not associated with higher rates of patient relapse.
Reference:
- Wadlow & Porter (2002) Biology of Blood & Marrow Transplantation vol.8(issue 12):637-647 “Umbilical cord blood transplantation: where do we stand?”
Among adult patients, perfectly matched bone marrow is preferable to cord blood, but mis-matched bone marrow and mis-matched cord blood yield comparable outcome. In Nov 2004, two studies were published in the New England Journal of Medicine which announced that cord blood transplants are suitable for adults who lack a perfectly matched HLA donor.
References:
- Laughlin MJ, et al. Nov2004; NEJM 351(22):2265-75. “Outcomes after transplantation of cord blood or bone marrow from unrelated donors in adults with leukemia.” This USA study found no difference between outcomes of cord blood transplants (150 patients) with 1 or 2 HLA mis-matches versus bone marrow transplants (83 patients) with one HLA mis-match. Please note, a perfect bone marrow match (367 patients) is still better than cord blood for adult patients.
- Rocha V, et al. Nov2004; NEJM 351:2276-2285. “Transplants of umbilical-cord blood or bone marrow from unrelated donors in adults with acute leukemia.” This European study compared 98 cord blood transplants (98 patients, 94% of them mis-matched) with bone marrow transplants (584 patients, all matched). There were no significant differences in occurance of chronic GVHD, transplantation-related mortality, relapse rate, and leukemia-free survival.
More in-depth answer: Cord blood Stem Cells may hold an advantage in telomere length. Telomeres are like molecular caps that tie off the ends of chromosones. As cells replicate, their telomeres get shorter. Literally, telomere shortening is the aging process at the cellular level. For example, when Dolly the sheep was cloned from a six year old cell, she was born with shortened telomeres, as if she was already six years old. Some researchers have suggested that telomere shortening in hematopoietic Stem Cell transplantation (ex: giving an old person’s Stem Cells to a young patient) is a potential mechanism for late graft failure.
References:
Another in-depth answer: Cord blood is more effective in repopulating the Stem Cell “reservoir”. Although it is well known that cord bood takes longer than bone marrow to engraft after transplant, a recent study indicates that in the long run (after one year) the cord blood does a better job of re-populating the body’s reservoir of blood Stem Cells. The cause for both of these effects is that the stem cells in cord blood would rather multiply than differentiate into more evolved blood cells.
References:
- Francesco Frassoni et al. 2003 Blood First Edition Paper: prepublished online 4/10/2003 DOI 10.1182/blood-2003-03-0720
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