New technology for processing bone marrow being studied at the University of Maryland Greenebaum Cancer Center and 17 other sites nationwide may increase the number of leukemia patients who can receive bone marrow transplants and enhance their chance of survival. Currently, only one out of four leukemia patients who may benefit from a transplant have a family donor.
Through an experimental process called immunomagnetic depletion, researchers hope to make bone marrow safer to give to unrelated recipients. The process involves the use of paramagnetic beads -- microscopic magnets that remove "T cells" from bone marrow. These "T cells" may cause the transplanted marrow to attack a recipients body, a condition known as graft-vs.host disease.
"Many patients who we could help with a bone marrow transplant lack a compatible donor," says Stanley Frankel, M.D., director of Clinical Studies at the University of Maryland Greenebaum Cancer Center and associate professor of Medicine at the University of Maryland School of Medicine. The Greenebaum Cancer Center is the only site in the mid-Atlantic region participating in the trial.
"This new technology may allow us to use distant family or unrelated donors by reducing the complications associated with a less than perfect match between donor and recipient," says Dr. Frankel.
If it proves effective, the new engineering technology may enlarge the potential donor pool beyond immediate family members. It also may open the door to transplantation for older patients currently ineligible to receive bone marrow transplants, due to the possibility of complications, and would enable patients with acute and chronic leukemia who were unable to identify a suitable donor to undergo the transplant procedure.
Bone marrow is a soft, fatty tissue inside bones that produces red and white blood cells and platelets. When a patient develops blood cell disease or when cancer treatment damages or destroys the bone marrow, a transplant with healthy bone marrow can save the patient's life.
About 70 percent of bone marrow transplants are performed using the patient's own marrow or stem cells from blood, but leukemia patients - because their disease involves the marrow itself - almost always rely on bone marrow donations from others. Finding a donor whose blood antigens match those of a patient can be a challenge.
Steven Ford, director of regulatory and clinical affairs for Chimeric Therapies Inc., the company that developed the new technology, says the immunomagnetic depletion process identifies the various blood cells within the marrow, marks the harmful "T cells" with paramagnetic beads and removes them from the mix.
The donor's marrow is collected at a site most convenient to them, then shipped to a Chimeric Therapies laboratory where the cells are processed and poured over an eight-inch-square magnet positioned above a pump. All of the "unmarked" cells continue to pass through as if in a strainer; those that have been marked are left behind. A very small portion of the "T cells" is then returned to replenish cells that the patient will need. Ford says the process is a delicate balancing act that, if successful, will aid the transplant process by removing potential barriers to success. After this 24-hour process is completed, the marrow is shipped to the institution performing the transplant.
Leukemia, one of a group of cancers of the blood, is often treated by a bone marrow transplant. An estimated 29,000 cases of leukemia are diagnosed in the United States each year. Though almost half of the patients potentially could be helped by a bone marrow transplant, only about 3,500 transplants are performed each year due to a shortage of compatible donors. Annually, 21,000 people die of leukemia. "If the need for a perfectly matched donor could be overcome, more patients could receive the treatment they need," Dr. Frankel says. "This option may let us expand our donor pool by utilizing donors who are not family relatives of patients or to use brothers, sisters, parents or children as donors even if they are less than a perfect match. This technique may also be a way of reducing side effects from bone marrow transplants and improving the outcome."