Finding The Ideal Donor For A Stem-Cell Transplant

A stem-cell transplant can offer the promise of a cure for many patients with blood cancers, such as acute myeloid leukemia (AML). It is also an extremely challenging course of treatment for patients to endure, requiring weeks in a sterile hospital environment followed by months of recovery at home, during which time the immune system is severely compromised.

When the transplant uses healthy blood-forming cells — the stem cells — from a donor, the procedure is called an allogeneic stem-cell transplant.

The big question is, of course, how do you find a matching donor?

SurvivorNet asked Dr. Caitlin Costello, a board-certified hematologist at UC San Diego Health m who specializes in treating a variety of blood cancers, including acute myeloid leukemia (AML), lymphoma, and leukemia.

Who is Your Ideal Stem Cell Donor?

“The ideal donor for an allogeneic stem cell transplant is someone who has more or less – let’s call it  – identical genes to you,” Dr. Costello said. “Because one of the greatest risks of a transplant is rejection.”

“When you think about kidney transplants or liver transplants, you think often about the patient rejecting the organ. But it’s actually the opposite in bone marrow transplant,” she notes. “In bone marrow transplant, one of the greater concerns is the organ — in this case, the bone marrow — rejects the patient.”

How Do You Reduce The Risk of Rejection?

Doctors look for donors with a “ten out of ten” genetic match. “The more alike you are, the less likely that rejection is to occur,” she says. “We’re talking about your major genetic makeup,” she explains: “Mom and dad each gave you five different genes, that is your DNA, your genetic makeup, your blueprint.”

“So when you don’t have a twin,” which is an ideal genetic match, “you have a brother or sister,” she says. “You’re looking for someone who received the same five major highways that you have from your mom and your dad.”

Siblings have a 1 in 4 chance of being a match. “So you have about a 25% chance of having your brother or your sister receive the same set of genes from your same parents.”

What if My Sibling Isn’t a Match — or I’m an Only Child?

There’s a 75% percent chance that a sibling won’t be a match. Your next option is an unrelated donor. “We end up going to a worldwide registry to look for volunteers out in the world who have volunteered to be donors,” Dr. Costello says. “And we can then test their major highways to see if they have the same – just coincidentally, maybe by heritage, you are of northern European ancestry, for example.

“We’re going to try and find someone who has those same ten major highways that you do,” says Dr. Costello. “So the more alike you are, the less of that risk of rejection that’s out there,” she says.

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