New research has shown that acute leukemia patients who are transplanted with two units of umbilical cord blood have significantly reduced risk of the disease returning. The current medical practice is the use of one unit of umbilical cord blood for treatment of patients who are at high risk for recurrence of leukemia and other cancers of the blood and bone marrow.

Previous research studies have shown that about 25 to 30 percent of patients suffer leukemia relapse after transplant. The relapse or disease recurrence rates are similar regardless of whether the stem cells used for transplantation are from bone marrow, peripheral blood, or umbilical cord blood.

The researchers studied 177 patients with an average age of 16yrs between 1994 and 2008, of which eighty-eight had acute lymphoblastic leukemia (ALL) and 89 had acute myeloid leukemia (AML). They compared the outcomes of patients who were transplanted with one verses two umbilical cord blood units. Forty-seven percent of the patients received one unit of umbilical cord blood; the remaining patients received two units. The choice to receive one versus two units was based on the number of stem cells contained in the umbilical cord blood. Since the number of stem cells needed for a successful transplant varies with the patient's weight, older patients and those who weigh more need more stem cells than infants and young children.

"Our analysis showed that patients in first or second remission from the leukemia had a significantly lower likelihood of leukemia recurrence if they were transplanted with two umbilical cord blood units than if they were transplanted with one (19 percent vs. 34 percent)," says Michael Verneris, one of the study leaders.

"We believe our finding provides evidence that using two units of umbilical cord blood for transplantation may be more effective in preventing leukemia relapse and gives hope to patients with hematological malignancies so that they may live cancer-free," he says.

Blood and marrow stem cell transplantation has been a mainstay treatment for patients with high risk leukemia and other hematological malignancies for the past 30 years. In the last decade, the blood in the placenta and umbilical cord has been collected and banked for public use. Now, umbilical cord blood is routinely used throughout the world as an alternative to bone marrow transplantation.

However, because of the limited number of cells in umbilical cord blood, this stem cell source has been reserved for young children and small adults. The practice of using two umbilical cord blood units (from two different individuals) was pioneered at the University of Minnesota approximately 10 years ago. By using two umbilical cord blood units, nearly all patients can now use this stem cell source for transplantation.

"Given that adult patients were more likely to receive two umbilical cord blood units and that they tend to have more aggressive leukemia, we think that the lower relapse rates with two umbilical cord blood units is remarkable," says Verneris. He notes that while promising, these results will have to lead to a national study comparing one verses two cord blood units in children with leukemia.

"Prior to the research done by my predecessors, the co-infusion of two umbilical cord blood units had not previously been performed," says Verneris. "We now know that without this double transplantation procedure, the majority of the patients treated would have had no other reasonable treatment option for their leukemia. The fact that they had less leukemia relapse was a wonderful surprise."
References:
1. Michael Verneris, et al. Relapse risk after umbilical cord blood transplantation: enhanced graft-versus-leukemia effect in recipients of 2 units. Blood, Nov 2009; 114: 4293 - 4299. DOI 10.1182/blood-2009-05-220525.