Advancements in Donor Selection for Hematopoietic Cell Transplantation

Recent progress in hematopoietic cell transplantation (HCT), likewise known as bone marrow transplantation, is refining donor selection strategies to improve survival rates and reduce the risk of relapse for patients with blood cancers and other hematological disorders. Historically, finding a perfectly matched donor was prioritized, often delaying potentially life-saving transplants. New data and approaches are shifting this paradigm, allowing clinicians to proceed with transplants using less-than-perfect matches when appropriate, ultimately getting patients treated more quickly.

The Shift Away from “Perfect” Matches

Traditionally, transplant centers focused on identifying donors with an 8/8 HLA (human leukocyte antigen) match – meaning a complete match at eight key genetic markers. While ideal, this could lead to significant delays, as finding such a match isn’t always immediate. A study presented at the 2026 Tandem Transplantation & Cellular Therapy Meetings highlighted a change in approach. Instead of waiting months for an 8/8 match, clinicians are now more confident in proceeding with mismatched unrelated donors (MMUD) when a patient is ready for transplant.

Understanding Donor Options

When a matched sibling donor isn’t available, several alternative donor options exist:

• Mismatched Unrelated Donors (MMUD): Donors who are not a complete HLA match.
• Haploidentical Donors: Family members (often parents, children, or siblings) who share approximately half of the patient’s HLA markers.
• Cord Blood: Blood collected from the umbilical cord after birth, rich in hematopoietic stem cells.

The ACCESS trial data suggests that outcomes are comparable whether a patient receives an 8/8 matched donor or proceeds with one of these alternative options, provided the transplant occurs when the patient is medically ready.

The Role of Prognosis-Based Categorization

The Blood and Marrow Transplant Clinical Trials Network (BMT CTN) study 1702, presented in 2025, further refined donor selection. This study categorized patients based on their likelihood of finding an 8/8 match. Those with a high probability of finding a perfect match were directed towards alternative donor pathways (MMUD, haploidentical, or cord blood). Interestingly, the study found that patients in both groups – those who received an 8/8 match and those who did not – proceeded to transplant at the same time. This underscores the importance of timely transplantation rather than prolonged searching for an elusive perfect match.

Current Trends in HCT and Cellular Therapy

According to the Center for International Blood and Marrow Transplant Research (CIBMTR), ongoing data collection and analysis continue to inform best practices in HCT and cellular therapy. Recent reports from CIBMTR detail trends in HCT and chimeric antigen receptor T-cell (CAR-T) therapy, including data from 2013-2023. As of May 2025, data indicates the following proportions of HCT types: autologous (63%), allogeneic (34%), and cord blood (3%).

Looking Ahead

The evolving landscape of donor selection for HCT emphasizes a data-driven approach, prioritizing timely access to transplantation. Continued research, spearheaded by organizations like CIBMTR and the BMT CTN, will further refine these strategies, ultimately leading to improved outcomes and a better quality of life for patients undergoing these life-saving procedures. The annual summary slides and reports from CIBMTR provide valuable insights into current activity trends and outcomes in the field.