Does donor type impact on outcomes of stem cell transplant for very high-risk acute lymphoblastic leukemia pediatric patients?

This study aimed to investigate if donor type impacts on the overall outcomes of allogeneic stem cell transplant for children with very high-risk acute lymphoblastic leukemia.  

This study concluded that donor type does impact on these patients and that worse outcomes are seen with mismatched donors.  

Allogeneic hematopoietic stem cell transplant (alloHSCT) is the only potentially curative treatment for very high risk (VHR) acute lymphoblastic leukemia (ALL). AlloHSCT involves taking stem cells from a donor and transplanting them into a patient in order to replace cells damaged by other cancer treatments and to boost the immune system. Cells can come from a matched donor (MD; genetically compatible unrelated donor), matched sibling donor (MSD; brother or sister genetically compatible), or mismatched donor (MMD; unrelated donor that is genetically not completely compatible).  

Stem cells can be acquired from different sources. Bone marrow (BM) is the tissue that contains stem cells. Peripheral blood stem cells (PBSC) are stem cells that have traveled from the BM to the blood. Ex vivo T-cell depleted PBSC are stem cells in the blood that are taken outside the body and manipulated to remove T-cells (immune cells). The removal of T-cells helps prevent graft-versus-host-disease (GVHD). GVHD is where the transplanted cells attack the patient's tissues. Another tissue that contains stem cells is the blood from the placenta and umbilical cord after birth. 

It was unknown if the donor type impacts on overall outcomes for VHR ALL pediatric patients.  

This study involved 569 pediatric patients with VHR ALL. Patients were treated with alloHSCT. Patients were followed up for an average of 5 years. 463 patients (81.4%) received a transplant from a MD or MSD and 106 (18.6%) received a transplant from MMD.   

Overall, 37.6% of patients were in complete remission after transplant. Stem cell source was BM for 58% patients, PBSC for 23.7%, ex vivo T-cell depleted PBSC for 10.9%, and cord-blood for 5%.  

Patients transplanted from an MMD had more advanced disease, more ex vivo T-cell depletion, and more chemotherapy-based conditioning regimen as compared to those transplanted from a MSD or MD. The 4-year rate of extensive GvHD was slightly lower (13%) for those who had a MSD/MD compared to 17% for those who had MMD.  

The 4-year event-free-survival (EFS; survival without complication from ALL) rate was 60% for those who had an MD/MSD compared to 42% for the MMD group. Overall, significantly more patients in the MSD/MD group were alive at 4 years (69%) compared to the MMD group (45%). 

There was no difference between groups in the 4-year rate of relapse. 

This study concluded that donor type impacts on overall outcomes of alloHSCT for VHR pediatric ALL patients. The authors concluded that patients who receive MMD stem cells have poorer outcomes than those who receive MD stem cells. However, MMD stem cells can offer similar chances of remission as MD cells.

These results are based on medical records from 2 different studies. The way in which stem cells were collected was not standardized. This might have influenced the results.