Unrelated umbilical cord blood as a valid alternative source for stem cell transplantation

This study examined different sources of allogenic (donor) stem cell transplantation for adult acute lymphoblastic leukemia (ALL) patients who are in first or second remission. Researchers reported no significant differences in survival across allogenic stem cell sources. In the absence of a matched related or unrelated adult donor, unrelated cord blood can be considered as a valid alternative source of stem cells.

In ALL the bone marrow makes too many lymphoblasts (a type of immature white blood cell). This type of cancer usually gets worse quickly if it is not treated. Stem cell transplantation is considered the most effective therapy for adults with high-risk ALL who have achieved complete remission after primary or secondary treatment (chemotherapy).

Stem cells can be found in the bone marrow and bloodstream, as well as in the umbilical cords of newborn babies. Stem cells can be harvested from the patient’s bone marrow or blood, or they can be harvested from a donor. An allogenic transplant involves donated stem cells. Ideally, the donor is genetically similar to the patient, such as a sibling. In some cases, stem cells from a mismatched related or unrelated donor are used. A mismatched donor will not be a close genetic match, because they do not share the same parents as the patient. The outcomes of mismatched donors for ALL are often less successful compared to genetically similar donors. Identifying predictors of transplantation success from a different stem cell sources is important to help improve clinical outcomes.

The aim of this study was to examine allogenic stem cell transplantation success in ALL patients who are in remission. Specifically, the authors aimed to compare outcomes of different allogenic stem cell sources.

802 ALL patients in first or second complete remission were included. All patients were treated with their first allogenic stem cell transplant. These were harvested from either umbilical cord blood (116, mostly mismatched), or from adult donors through bone marrow (140 patients) or blood cells (546 patients, matched or mismatched). The average time from diagnosis to transplantation was 8 to 11 months.

No significant differences in overall survival rates (proportion of patients who did not die from any cause since treatment) were observed. The estimated 3-year probability of survival rates were 44% for cord blood recipients, 44% for matched adult donors, and 43% for mismatched adult donors.

Overall, there were 30 engraftment failures. This means the stem cells did not begin to make blood cells. 3% of matched adult donor recipients and 2% of unmatched adult donor recipients showed graft failure. This was significantly lower compared to cord blood recipients (8%). Cord blood transplants also tended to engraft slower.

However, cord blood transplants were associated with significantly fewer cases of acute graft-versus-host disease (when donor cells attack the organs of the patient). Chronic graft-versus-host disease (occurs a few months after transplant, disease relapse and transplant-related mortality were similar for each group. 

Researchers concluded that the survival of cord blood graft recipients was similar to that of recipients of matched or mismatched adult donor grafts. Researchers advised that cord blood can be considered as a valid alternative source of stem cells when there is no matched unrelated adult donor available.