Every day thousands of babies are born in hospitals across America. These births offer opportunities to cure patients of leukemia and other life-threatening diseases. The opportunities lie in the routinely disposed placentas and umbilical cords. Researchers have found these to be rich sources of immature blood-forming cells (stem cells) that can be transplanted to patients needing bone marrow transplants as a potential cure for leukemia or other diseases. Instead of using bone marrow cells, transplant physicians are now using umbilical cord blood (UCB) cells, also called placental cord blood cells.
Bone marrow transplantation (BMT) is now a standard treatment option for patients with certain types of leukemia. In the transplant process, a patient receives high doses of radiation therapy and/or chemotherapy to prepare the body for the transplatn and hopefully to kill whatever leukemia cells remain in the body. The normal bone marrow is killed as an innocent bystander. The marrow transplant is given to rescue or replace the normal bone marrow, using marrow collected from a matched or partially-matched relative, from a matched or partially-matched unrelated adult donor, or sometimes from the patient (which has been collected before the radiation and/or chemotherapy). The transplanted cells then begin to grow in the patient's body and to function as the body's blood factory, making blood cells that move into the circulatory system, performing functions that include carrying oxygen, fighting infection, and clotting the blood.
In an umbilical cord blood transplant, the patient receives the
same kind of preparative radiation therapy and/or chemotherapy,
but instead of bone marrow, the patient receives umbilical cord
blood cells. Similar to transplanted
bone marrow, the UCB cells begin to grow in the patient's body and make blood cells.
The first transplant of umbilical cord blood was performed in 1989 in a patient with a nonmalignant blood disease. The umbilical cord blood was collected when his baby sister was born and was frozen in a laboratory until the transplant. Since then, more than 65 transplants using related cord blood have been performed in children and young adults with leukemia and other blood diseases, other cancers, and certain inherited metabolic diseases.
Unrelated Umbilical Cord Blood
Even more exciting is the use of unrelated umbilical cord blood in transplantation. In 1992, an unrelated placental blood bank was established by Dr. Pablo Rubinstein at the New York Blood Center, with funding from the National Institutes of Health. Approximately 5,300 units of umbilical cord blood have been collected at Mt. Sinai Hospital in New York City, tested for a variety of blood-borne diseases (such as HIV), tissue typed, frozen, and stored at the New York Blood Center. In August 1993, the first unrelated umbilical cord blood transplant in the world was performed at Duke University, using frozen unrelated umbilical cord blood from the Placental Blood Project's bank, in a 3-year-old patient with relapsed leukemia. Since then, more than 100 unrelated umbilical cord blood transplants have been performed. The longest survivor to date is a boy who received his unrelated umbilical cord blood transplant for infant leukemia in September 1993; he is a healthy, active, leukemia-free 4-year-old.
Researchers are excited about the possibilities of umbilical cord blood transplantation for a number of reasons. First, the cord blood can be collected with no risk to the donor. The cost of this collection is also substantially less than the harvesting of bone marrow, which requires anesthesia and a short hospital stay. Second, widespread collection of umbilical cord blood, especially in metropolitan areas, can significantly address the needs of minority individuals who need transplants. The National Marrow Donor Program, the largest donor registry in the United States, is actively recruiting minority donors, but the vast majority of registered volunteer donors are Caucasian. While it is not essential that ethnic backgrounds of donors and recipients match, there are certain tissue types that are more common in a given ethnic group, and minority and mixed-race individuals in need of unrelated marrow transplantation often cannot find donors through the National Marrow Donor Program.
Advantages of Umbilical Cord Blood
Umbilical cord blood transplantation also appears to offer advantages to the transplant recipients. While relatively few unrelated cord blood transplants have been performed, physicians are finding that UCB transplants can be successful even when the tissue types of the cord blood and the donor are less well matched than with marrow transplantation. Of the 35 unrelated umbilical cord blood transplants we have performed at Duke, only one has been a complete (6/6 antigen) match, and yet more than 70% of the transplants have been successful. It also appears that a major, and potentially fatal complication of transplantation, graft-vs-host disease, may occur less frequently and with less severity in UCB transplant recipients. UCB is also less likely to be contaminated with viruses like cytomegalovirus, which may cause serious infections in transplant recipients.
Although UCB appears very promising, several questions about its use remain the subject of current research. The most pressing is whether UCB can be used to transplant adults. Within the past year, a few UCB transplants have been successfully performed in older children and adults, but further studies are necessary to determine the extent to which this is possible.
What does the future hold? In the short-term, the National Heart, Lung and Blood Institute (part of the National Institutes of Health) is planning to find several additional cord blood collection banks. This will enable more people who need transplants, but lack a related bone marrow donor, to find a source of transplantable cells and maybe a chance for a cure. Laboratory work is in progress to see whether cord blood cells can be multiplied before the cells are transplanted; if successful, this could ultimately mean that a single unit of umbilical cord blood might be used to transplant more than one person. As clinical trials of umbilical cord blood transplantation progress, researchers may find ways to make UCB transplantation even more successful in curing leukemia and other diseases.
For more information on UCB transplants at Duke University Medical Center and cord blood storage, contact Connie Stephens at (919) 684-8963. For more information on the New York Blood Center UCB Bank, please call (212) 570-3230.
Statistics Source: John Wagner, md, International Cord Blood Registry, University of Minnesota, Box 366, Minneapolis, MN 55455.
Reprinted, with permission, from the Leukemia Society of America from the spring 1996 issue of Newsline, the Leukemia Society's national quarterly newsletter.