Who is eligible for a bone marrow transplant?
How does a patient find a bone marrow donor?
We consider disease relevant factors and patient relevant factors to best determine who is the candidate for allogeneic transplantation.
If we are talking about myelodysplastic syndrome, then not every MDS patient is a candidate for transplant. The reason being, if patients have lower risk disease, they can have complications from the transplant procedure, and immediately after diagnosis, that's not the right procedure to proceed with as a treatment choice.
But if patients have higher risk disease, then that is determined by blast percentage, which is cancer cells in the bone marrow, as well as the need for transfusions such as red blood cells, platelet transfusions, or chromosomal abnormalities and mutational abnormalities. These all can help us determine who are higher-risk patients, and these patients would benefit from a disease standpoint with allogeneic transplant in terms of survival.
We also take into account patients' age as well as comorbidities at the time of assessment. If patients have multiple comorbidities such as heart failure, kidney failure on dialysis, or liver cirrhosis, they might not be good candidates for the transplant procedure.
Otherwise, if they have high-risk disease and they are relatively healthy, most of the time, up to age 75, most patients will benefit from transplant and they are eligible to proceed after initial assessment of safety.
There is special testing that is done on chromosome number six to determine what tissue type the individual is. We have the National Marrow Donor Center where there are about 3 million donors, and they can actually use that information to match with any existing donor in terms of tissue type.
Or if we are using family members, then we are typing family members as well. And then we look into these called HLA markers to determine if a family member is fully matched, half-matched, or mismatched to determine who could be a good candidate for serving as a donor for patients.
It also depends on how many potential siblings patients have. Generally, about 30% of patients will have a fully matched family donor available to them if they have a number of siblings. One individual sibling can be a maximum of 25% fully matched to the patient. About 50% of them can be half-matched to the patient.
So if patients are older and their siblings are not healthy enough for donation or they have malignancies themselves, then we directly go to the pool of National Marrow Donors, where we can find up to 70% of matched donors available if the person is Caucasian. In Hispanic patients, about one-third of them will have a matched donor available in the registry, and African-Americans will have about 25%.
So race and ethnicity matters a lot in terms of the availability of donors in the registry. But since then, we have expanded the pool of donors, allowing the use of haploidentical, meaning half-match, donor options. Most of the patients, more than 90%, currently have a donor available, and rarely do we find patients who don’t have a donor nowadays for a transplant procedure just because of not having donor availability.
HealthTree • March 14, 2025