Does Donor Age Matter for Stem Cell Transplant Success? What the Latest Research Says 

Stem cell transplants can be life-saving for people with blood cancers such as acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and acute lymphoblastic leukemia (ALL). One of the most important factors affecting transplant success is the donor.

Why transplant programs have focused on younger donors

An allogeneic hematopoietic cell transplant (HCT) is a transplant using stem cells from another person. Transplant programs typically choose donors younger than 35 when possible. This decision is based on the fact that younger donor cells are generally more robust. Their cells are better able to rebuild the recipient’s blood system.

However, this rule may exclude many healthy older donors who could still provide effective stem cells. New research suggests that some older donors may have cells that would be just as helpful. 

To determine which donors are eligible, researchers are looking at a part of chromosomes called telomeres, which are markers of biological aging. What are telomeres?

Telomeres protect the ends of chromosomes, the structures that hold our DNA. You can think of them like the plastic tips at the end of shoelaces that keep them from fraying. 

Each time a cell divides, telomeres become slightly shorter. Over time, shorter telomeres are linked to aging cells and reduced ability for cells to divide and repair tissues. 

After a stem cell transplant, donor stem cells must multiply to rebuild the patient’s blood and immune system after treatment. Telomere length is one way to measure how well cells will be able to complete that important task.

What is more important? Biological age measured through telomere length or chronological age? 

A recent study looked at stem cell donors aged 35 years and older and the recipients of their cells. The study included 7,373 donors whose stem cells were used in transplants for people with AML, MDS, and ALL. It included all different types of donor transplants,  including: 

• Matched unrelated donors
• Matched related donors
• Mismatched donors

Haploidentical donors, which are donors that are a parent or sibling. The study found that donors with longer telomeres had better transplant outcomes, even among donors aged 35 or older.

Specifically, longer donor telomere length was associated with:

• Lower risk of non-relapse mortality (NRM), meaning death unrelated to cancer returning.
• Lower risk of primary graft failure, when the transplanted cells fail to grow and produce new blood cells.

In fact, recipients of grafts from donors with longer telomeres had about a 10% lower risk of non-relapse mortality compared with those receiving cells from donors with shorter telomeres.

Can longer telomeres improve graft success?

Stem cells with longer telomeres may have a greater ability to divide and rebuild the blood system. This process is called engraftment. If stem cells cannot divide enough times, graft failure can occur. The study supports the idea that telomere length is a good measurement of how well stem cells will grow after transplant.

Does telomere length affect relapse or graft-versus-host disease?

Telomere length did not significantly affect some other transplant risks, such as:

• Severe acute graft-versus-host disease (GVHD)
• Chronic GVHD
• Risk of leukemia relapse

This suggests that telomere length mainly influences how well stem cells grow and engraft, rather than immune-related transplant complications.

Could telomere testing help choose better donors?

This study opens a possibility to analyze telomere length and use it as a biomarker. This means telomere length could be a measurable feature that helps guide medical decisions. Instead of relying only on age cutoffs, transplant teams could potentially use this knowledge to personalize donor selection.

If validated in future studies, telomere testing might help:

• Identify high-quality donors among older adults.
• Expand the pool of eligible stem cell donors.
• Reduce the risk of graft failure.
• Improve survival after transplant.

Research like this opens the possibility to more personalized and precise medicine

While more studies are needed before telomere testing becomes routine, this work highlights an encouraging direction: using deeper biological insights to improve transplant success and expand options for patients.

Stay updated with more research insights, community events, and treatment approvals with our newsletter. 

SUBSCRIBE TO MDS NEWSLETTER

SUBSCRIBE TO AML NEWSLETTER 

Source: Longer telomeres in donors aged ≥35 years reduce graft failure and non-relapse mortality
after allogeneic HCT