University of Florida Physicians Use New Device to Purify Bone Marrow For Transplantation

GAINESVILLE, Fla.---University of Florida physicians are testing a new way of purging tumor cells from bone marrow.

The method could yield a "cleaner" bone marrow sample and reduce treatment-related side effects for patients undergoing bone marrow transplantation, UF researchers report.

The technique, known as the CD-34 positive selection method, is used for patients who are donating their own bone marrow to be given back to themselves at a later date, also known as autologous bone marrow transplant.

A 47-year-old North Florida man battling multiple myeloma was the first to undergo a transplant involving the new approach at Shands at UF.

Multiple myeloma is characterized by the uncontrolled spread of certain white blood cells -- plasma cells -- in bone marrow. Plasma cells ordinarily make antibodies, disease-fighting agents that normally guard against infection. But because their immune system functions abnormally, patients with multiple myeloma are especially prone to infection.

Despite weeks of chemotherapy, fully a third of the cells in the man's bone marrow were still malignant. So doctors took a two-step approach to cleansing the marrow's most primitive cells -- the stem cells. (These are in the earliest stages of development and have the ability to evolve into an array of blood cell types as they grow and mature.)

First, the patient was given injections of growth factors daily for five days to move the stem cells into the blood and reduce the level of tumor contamination. The cells were collected by apheresis, a procedure that separates them from other blood components. This first step decreases the level of tumor cells mixed with stem cells but does not eliminate it. Secondly, the blood stem cells were run through the CD-34 device, similar to a long column with a collection area for cells at the bottom.

The device was recently approved by the Food and Drug Administration.

"With the CD-34 selection procedure, we use a column containing antibodies -- which recognizes a certain substance or 'antigen' that is unique to the membrane of stem cells," said John Wingard, director of the bone marrow transplant program at Shands. "That allows us to put about two liters of blood or bone marrow cells in the device and end up with a teaspoon that only contains the stem cells. Everything else -- the other cells not necessary for the transplant and malignant cells -- flows through."

Previous methods used a bone marrow sample containing a wide variety of cells, and did not ensure the transplant was completely free of tumor cells, Wingard said. Moreover, those techniques typically damaged some normal stem cells. Thus, efforts to clean the sample prior to transplantation often prolonged the patient's hospital stay.

"With this approach, we think we give a cleaner stem cell product that is less likely to have tumor cells in it," he said. "We are using it for selected cases where we believe there's a strong likelihood there might otherwise be significant amounts of tumor cell contamination."

Other possible benefits: a lower risk of rejection and reduced side effects from transplantation. Because stem cells alone are used, the sample's volume is naturally smaller, reducing the amount of preservative needed to protect the cells when they are frozen for storage prior to transplantation. The preservative can cause side effects in some patients, Wingard said.

If it works, the approach also could benefit patients stricken with cancer or other blood disorders, including non-Hodgkin's lymphoma, multiple myeloma, some breast cancer cases, and possibly tumors such as neuroblastoma that involve the bone marrow.

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