New Approach Works Against Leukemia, Lymphoma

FRIDAY, July 8, 2005 (HealthDay News) -- Experts have long known that blood stem cells extracted from umbilical cords can help beat back deadly lymphomas and leukemias. Unfortunately, there's always been one roadblock: the average umbilicus contains only enough stem cells to help the smallest patients, mainly children.

That's why the early results of a new study are so encouraging. Researchers at the Dana-Farber Cancer Institute in Boston say they have successfully treated adult blood cancer patients using stem cells extracted from two separate cords.

"The remarkable thing about it is that there are no apparent adverse consequences of using two cords, and the new blood cells seem to come in faster, with more rapid engraftment," explained Dr. Robert Soiffer, chief of hematologic malignancies at Dana-Farber.

He said the majority of patients receiving the double-cord stem cell transplant are still alive and doing well one year after treatment.

Researchers led by Dr. Karen Ballen are still tabulating their data and the full results of the study will probably not be announced until December, Soiffer said. However, he gave reporters a preliminary sketch of the findings at a recent National Cancer Institute-sponsored seminar held at Dana-Farber.

Another expert called the results "very promising."

Because the majority of leukemia and lymphoma patients are older adults, "this opens up the possibility of treating the primary patient set" with cord blood-derived stem cells, explained Louis DeGennaro, vice president of research at the Leukemia & Lymphoma Society.

"This combining of cord blood collections has such great promise," he said. "It's exactly what you need -- more cells."

The umbilicus is a rich source of stem cells destined to become blood cells. Soiffer also pointed out that cord blood has a relatively low number of immune T cells -- key players in a dangerous post-transplant immune response called graft-versus-host disease that can threaten patients' lives.

For those two reasons, transplanting stem cells from the umbilicus means the threshold for a proper "match" between donor and patient is much lower than if cells were sourced from adult bone marrow.

"That means more patients can be treated," DeGennaro said, "especially patients who are older than what's currently considered the age cut-off for transplant."

Another advantage of umbilical cord transplant: no risk whatsoever to the donor.

And yet doctors began realizing early on that a single cord simply does not contain enough stem cells to quickly repopulate the devastated immune systems of adult patients.

"You ended up having slower engraftment," DeGennaro explained. For patients with blood cancer, that kind of delay can be deadly, he said. "It opens the patient up to infection because their immune system is compromised, and there's also the risk of disease recurrence."

But Ballen's team at Dana-Farber may have come up with an obvious solution. Working with 27 patients suffering from a range of leukemias or lymphomas, they obtained blood stem cells sourced from two separate cords for each patient. These stem cells were then infused into the respective patient in a simple intravenous procedure.

Although exact numbers aren't yet available, Soiffer said that, one year later, "we have seen a relatively fast engraftment and the graft-versus-host rate has been tolerable."

Furthermore, "the initial survival over one year has been very encouraging -- the large majority of patients are still alive," he said.

Soiffer said that, so far, there seem to be no extra complications in using two cords instead of one. One interesting finding: Although stem cells from both cords contribute to a new, healthy blood supply over the first few months, Soiffer said that, "ultimately, it appears that cells from one cord predominate and end up taking over. And right now we can't predict which cord that will be."

DeGennaro applauded the effort, but cautioned that the demand for usable cords -- which parents donate to public cord blood banks -- may soon outstrip supply.

"Availability is an issue," he said. He and Soiffer agreed that most U.S. hospitals are simply not equipped to extract and properly store cord blood stem cells. That means that parents at many centers may not be able to donate the lifesaving cells.

"There are some new initiatives under way, however," DeGennaro said. "Right now, Senator Chuck Schumer (D-N.Y.) is co-sponsoring the Cord Blood Stem Cell Act, which hopes to create -- if and when it is passed -- a network of qualified cord blood banking centers nationwide."

"Those would be centers for preparing and distributing cord blood cells for treatment. Something like that would really fill the availability gap," he said.

More information

For more about using stem cells transplants to fight blood cancer, head to the Leukemia & Lymphoma Society.