‘No difference between unrelated foreign donor and half-matched donor in HSCT’

A study found no differences in hematopoietic stem cell transplantation (HSCT) outcomes whether the transplant source was an international donor or a haploidentical donor.

The findings support the view that if there is no domestic matched donor, a half-matched donor could be an alternative to an unrelated international donor.

On Monday, the National Evidence-based Healthcare Collaborating Agency (NECA) released the study results that analyzed the optimal use of various transplant sources in HSCT.

HSCT is used to treat blood diseases such as leukemia, malignant lymphoma, and aplastic anemia. HSCT is divided into autologous HSCT from the patient himself or herself and allogeneic HSCT from a donor.

In allogeneic HSCT, an identical match in the donor and recipient tissue types is ideal because an immune response does not occur. In this case, treatment results are excellent.

However, as it is often difficult to find a fully matched donor, a half-matched donor has been suggested as an alternative. Still, this method has not been supported with sufficient evidence so far.

NECA’s study analyzed the overall survival, transplantation success rate, and adverse reactions of HSCT according to different transplant sources -- sibling donor (completely matched), unrelated domestic donor (completely matched), unrelated international donor (completely matched), and half-matched donor (partially matched).

Given the difficulty of finding a sibling donor and an unrelated domestic donor, the researchers checked whether a haploidentical donor could be an alternative to an unrelated international donor.

The research team assessed the data of 2,278 patients who underwent allogeneic HSCT between January 2015 and June 2018, among those registered with the Korean Blood and Marrow Transplant Registry (KBMTR). The analysis was on their engraftment rate, overall survival, side effects, GVHD-free Relapse-free Survival (GRFS), and survival rates among transplant sources by disease type.

The results showed that HSCT recipients from sibling donors and unrelated domestic donors had better survival rates than those from the other two transplant sources.

However, there was no difference in HSCT outcomes between international unrelated donors and half-matched donors.

The engraftment rate after transplantation was over 90 percent in all transplant sources.

The overall survival rate of HSCT recipients from sibling donors was 68 percent, and that of unrelated domestic donors, 68.9 percent.

In contrast, the figure was 57.1 percent among HSCT recipients from unrelated international donors and 57 percent among those from half-matched donors. The difference between the two was statistically insignificant, NECA said.

The cumulative incidence of moderate or severe acute graft-versus-host disease, a typical side effect of transplantation, was 21.4 percent in HSCT from sibling donors and 29.6 percent from unrelated domestic donors, respectively, and 40.6 percent and 34.3 percent in HSCT from international unrelated donors and haploidentical donors, respectively.

GRFS three years after transplantation was 44.8 percent in those who had HSCT from sibling donors. 49.9 percent from unrelated domestic donors, 40 percent from international unrelated donors, and 41.6 percent from half-matched donors. There was no meaningful difference between international unrelated donors and half-matched donors.

The latest study was a follow-up to the previous research and a roundtable meeting. The analysis was based on the largest registry data in Korea regarding HSCT.

Professor Moon Joon-ho of the Hemato-Oncology Department at the Kyungpook National University Hospital, who is the principal investigator of the study, said, “As transplantation has to be performed quickly in real clinical settings, using a haploidentical donor as an alternative to an unrelated international donor could help patients get the timely treatment.”

Co-principal investigator Shin Sang-jin at NECA said the study provided evidence to select a desirable donor for HSCT.

“The reason that survival rates of HSCT recipients from unrelated international donors and half-matched donors were lower than that of those from sibling donors and unrelated domestic donors was that the patients who used the former two transplant sources had poorer disease conditions, and this needs a careful interpretation,” Shin noted.