Infants Benefit From Stem Cell Transplants Using Cord Blood

SAN FRANCISCO—Umbilical cord blood from unrelated donors is an excellent source of hematopoietic stem cells for infants with either leukemia or an inherited disorder that can be treated with stem cell transplantation, Joanne Kurtzberg, MD, said at the 42nd Annual Meeting of the American Society of Hematology (ASH).

Dr. Kurtzberg, director, Pediatric Bone Marrow Transplantation Unit, Duke University Medical Center, noted that donor umbilical cord blood offers patients with hematologic cancers another treatment option when a bone marrow donor cannot be found. She was one of the first researchers to test this procedure, and has met with considerable success in refining the technique over the last several years.

"Infants and toddlers represent a unique group of recipients because their size enables delivery of a cell dose approaching the dose given in a bone marrow transplant," Dr. Kurtzberg said.

To determine which factors might affect treatment success, the investigators in this multicenter study reviewed the cases of 157 infants (less than 2 years of age)—41% transplanted for leukemia and 55% transplanted for genetic diseases. Banked umbilical cord blood for the transplants came from the Placental Blood Program of The New York Blood Center.

A total of 49 infants received total body irradiation plus chemotherapy, while 105 received only chemotherapy as preparation for transplant. Nine infants received grafts that matched their tissue type in 6 of 6 major HLA antigens; 55 of the transplants matched in 5 of 6 antigens, and 38 matched in 4 of 6 antigens.

Almost all of the patients (95%) achieved myeloid engraftment within a median of 21 days. More than 96% of the patients in all groups achieved absolute neutrophil counts of at least 500/mm³ and platelet counts of 50,000/mm3 by 6 months post-transplant.

Only 15% of patients in the study developed acute graft-vs-host disease (GVHD), and there were no cases of extensive chronic GVHD.

The overall rate of relapse after transplant for the infants with leukemia was 23%. The overall event-free survival rate at 3 years was 52% for all of the patients. Those infants with leukemia had a 3-year event-free survival rate of about 35%.

Aside from cell dose, Dr. Kurtzberg said, the main predictor of a favorable outcome was the absence of total body irradiation. Infants receiving only chemotherapy, without irradiation, prior to transplant had a 59% 3-year event-free survival rate vs a rate of 47% in the group receiving irradiation (P = .006).