Results of a recent study indicate that better matching criteria may decrease the risk of death in patients with myelodysplastic syndromes and other blood cancers undergoing umbilical cord blood transplantation.

Specifically, the study authors found that patients who matched their donors in the gene HLA C had a decreased risk of death compared to patients who did not match their donors in that gene.

Based on their findings, the study authors suggest that the current donor matching system should include matching at HLA C in order to minimize the risk of transplant-related death.

“When searching for an umbilical cord blood unit for transplantation, consider matching the unit and patient. If these [matching] units are unavailable, consider matching at HLA C and HLA DRB1. Having a mismatch at HLA C and HLA DRB1 had the worst outcome,” said the study’s lead author, Dr. Mary Eapen of the Medical College of Wisconsin.

Umbilical cord blood transplantation has recently been developed as a popular alternative to stem cell transplantation for patients with myelodysplastic syndromes (MDS) and other types of blood cancers who cannot find a matched donor.

“Not everybody has a fully matched donor,” explained Dr. Eapen.  “Most physicians look for a matched adult unrelated donor if there isn’t a matched family donor.  If a matched adult unrelated donor is not available, then they look for a cord blood unit.” 

In order to determine a matched donor for a stem cell recipient, physicians compare the genetic sequence for a cell surface protein called the human leukocyte antigen (HLA). This protein helps the immune system tell the difference between the body’s own tissues and foreign substances.

Previous research has shown that patients who undergo stem cell transplantation with an HLA-mismatched donor experience more serious transplant-related complications and are at a higher risk of death.

The authors of the current study found in earlier research that umbilical cord blood transplantation with an HLA-mismatched donor produces similar leukemia-free survival rates but is associated with more transplant-related deaths, compared to stem cell transplantation with an HLA-matched donor.

In order to decrease the high transplant-related death rate associated with umbilical cord blood transplantation, researchers are currently investigating the impact of improving matching between donor and recipient. The screening process for selecting a donor currently does not include matching at HLA C, one of the major classes of HLA proteins.

In the current study, researchers evaluated the impact of donor matching at HLA C on outcomes after umbilical cord blood transplantation. They retrospectively analyzed data from 803 patients with various forms of blood cancers, of which 9 percent had MDS. Ten percent were older than 41 years old.

Of the 803 patients included in the study, 9 percent had a donor matched at all four protein variations, HLA A, B, C, and DRB1. This population had a three-year transplant-death probability of 9 percent.

The rate of transplant-related death increased significantly with HLA C mismatching. In total, 68 percent of patients had a donor mismatched at protein HLA C. The three-year transplant-death probability for patients with no other mismatches besides HLA C was 26 percent. This probability increased to 31 percent for patients with one other mismatch besides HLA C.

Patients who underwent transplantation with an HLA C-mismatched donor also more commonly experienced graft failure, infections, and organ failure.

The three-year overall survival probability was 51 percent for patients with HLA C matched but another HLA class mismatched. This probability decreased to 37 percent for patients with HLA C mismatched and another HLA class mismatched.

The researchers found that the probability of overall survival improved with transplantation at an earlier disease stage and with younger patient age.

For more information, please refer to the article in The Lancet Oncology (abstract).