The two types of transplants used for children with leukemia are syngeneic transplants (from an identical twin) and allogeneic transplants (from a person who is not an identical twin).

Syngeneic transplant

Syngeneic transplants are those in which the stem cell donor is the identical twin of the child with leukemia. These are the least complicated transplants because there is no risk of rejection or graft-versus-host disease (GVHD). Recovery is usually rapid after a syngeneic transplant. However, this type of transplant is often not favored because there is minimal GVL effect and a higher risk of relapse after transplant.

Jeremy had a syngeneic transplant from his identical twin brother as his donor to treat the AML that developed after treatment for Ewing’s sarcoma. He received cyclophosphamide and radiation in his conditioning regimen. One of the worst side effects he experienced was the nausea and vomiting. He was released from the hospital on Day 9, readmitted on Day 11 because of an infection, and discharged again on Day 12. We stayed near the hospital, and then we were allowed to go home on Day 30. He has done very well.

Allogeneic transplant

Allogeneic transplants are those in which the stem cells come from a person who is not the child’s identical twin. Thus, the donor could be a sibling, parent, close relative, or an unrelated individual. The risk of complications increases if the donor is not a full match.

Allogeneic transplants can be further categorized based on the source of donor stem cells. Potential stem cell sources include:

• HLA-matched bone marrow or peripheral blood from a sibling
• HLA-matched bone marrow or peripheral blood from an unrelated adult
• Umbilical cord blood from a relative (e.g., sibling) or unrelated child
• Haploidentical (half-matched) bone marrow or peripheral blood from a relative

Adele was 5 ½ years old at the time of her transplant. Donor marrow was harvested from her brother Ben, 2 ½ at the time. Harvesting took approximately one hour, and after the marrow was prepared for infusion, Adele received it (about 45 minutes later). The actual infusion was very simple—just hanging an IV bag. The doctor and nurses were, understandably, extremely careful with it, and it was very dramatic!

One hour after completion, Adele could get up, and she and Ben immediately went running to the playroom! She had not crashed yet from the preparative chemotherapy, which had been completed two days before. Just like her response to most of the treatment, however, this was not the norm. The nursing staff said they’d never seen a kid who felt well enough to do that following a transplant. Adele first showed something above a zero ANC [absolute neutrophil count] on Day 15. From then on, she improved quickly and steadily. She was released about six weeks after transplant, and met her goal of being at home and better (at least not sick!) for her sixth birthday. Because Adele showed basically no signs of graft-versus-host disease, she was taken off almost all meds early.

HLA-matched sibling. The first step in identifying a suitable stem cell donor is to perform HLA typing on all siblings who have the same mother and father as the child with leukemia (called full biologic siblings). If a match is found, then that brother or sister will likely be used as the stem cell donor.

Jody’s 2-year-old brother, Christoph, was a perfect match. I stayed with him when he donated marrow, and my husband stayed with Jody. Christoph seemed to handle the marrow donation easily. Although he had some nausea in the recovery room, he was up and running around late that afternoon saying, “I the donor.” He felt very proud. I knew he was somewhat sore because he said, “My diaper hurts.”

Umbilical cord blood. Placental blood/umbilical cord blood is a rich source of stem cells. Some institutions perform transplants using the umbilical cord blood obtained during the birth of a sibling (and frozen for future use) or from preserved unrelated donor cord blood. The advantage of cord blood transplant is that the cord does not have to be a perfect match. The number of stem cells in cord blood is usually sufficient for most children, but it may not be adequate for larger children or teens.

Our 15-month-old son, Garrett, was diagnosed with AML and central nervous system involvement. He relapsed on treatment, and the doctors recommended a cord blood transplant. There was one perfect match in Barcelona, Spain. I wanted to fly to Barcelona and hug everyone I could see. He was so sick during treatment, which included a trip to the ICU [intensive care unit] and several periods of extended hospitalization for complications, that the transplant was almost anticlimactic. He had TBI [total body irradiation], then chemotherapy. He engrafted on Day 12 and was out on Day 21. He did wonderfully—he only got one fever, no GVHD, no other problems. He has not been inpatient since, and he’s now in college.

When transplanted stem cells enter the bloodstream, make their way to the bone marrow, and start making new blood cells, it is called engraftment. This usually occurs 10 to 30 days after a stem cell transplant. Engraftment after an umbilical cord blood transplant may take longer than with SCTs from other sources, but cord blood transplants may cause less GVHD than allogeneic transplants. In addition, cord blood is rarely contaminated by viruses such as cytomegalovirus (CMV) or Epstein Barr virus (EBV) that can cause life-threatening complications after a SCT. Cord blood SCT is one of many promising new directions in the research efforts to improve SCT. For information about public, private, and family cord blood banks, visit the Parent’s Guide to Cord Blood Foundation at www.parentsguidecordblood.org.

Christopher received his cord blood unit after three days of TBI, testicular radiation, and other conditioning with chemotherapy. He had a feeding tube inserted during his final TBI, so we didn’t have to worry about eating. He engrafted on Day 10 and had a little GVHD, which was treated with prednisone. After he was discharged from the hospital, he was readmitted a few times for fevers. Overall it went very well. Our biggest problems now are fixing his cataracts, waiting for results of his endocrine tests and bone tests, and getting educational support.

Unrelated adult volunteer. Large registries of adult volunteer donors have been created in the United States and other countries. An HLA-matched or very nearly matched donor can often be identified through a computer-based search of those registries. More HLA proteins are evaluated with this type of donor, so you may hear the transplant team talk about an “8/8” or “10/10” match.

Haploidentical transplant. Haploidentical transplants are a newer form of treatment for children who do not have a matched donor. This type of transplant uses stem cells from a parent or sibling who is only half-matched with the child needing a transplant. The procedure is similar to an allogeneic transplant except that because the donor and recipient (child) are not fully matched, something must be done to remove T cells from the stem cell “graft” to prevent GVHD. This can be done by processing the graft to remove T cells before it is given to the child, or by administering a drug called cyclophosphamide after the transplant to kill T cells in the bloodstream.