Stem cell transplantation, performed as support for high-dose chemotherapy, is a treatment option for many patients with myeloma. Studies have shown that this treatment improves both the response rate and survival in myeloma over that obtained with conventional chemotherapy.
A stem cell transplant is a procedure that is used in conjunction with high-dose chemotherapy, which is frequently more effective than conventional chemotherapy in destroying myeloma cells. Because high-dose chemotherapy also destroys normal blood-producing stem cells in the bone marrow, these cells must be replaced in order to restore blood cell production.
The first step in the process of stem cell transplantation is the collection of stem cells from a patient or a donor. When a patient's own stem cells are used, they are frozen and stored until needed. Stem cells can be collected from a donor when they are needed. The patient then receives high-dose chemotherapy and the stem cells are infused into the patient's bloodstream. The stem cells travel to the bone marrow and begin to produce new blood cells, replacing the normal cells lost during high-dose chemotherapy.
Stem cell transplantation is a complex process that involves several steps. The process is similar for both autologous and allogeneic stem cell transplants. However, in the case of autologous transplants, the patient will undergo the stem cell collection procedure prior to receiving high-dose chemotherapy and their cells will be frozen and stored until needed. In allogeneic transplants, a stem cell donor will typically undergo the collection procedure just before the transplant will be performed. Since autologous transplants are performed more frequently, we'll focus mainly on this process and indicate where allogeneic transplants are different.
Most of the stem cells in the human body reside in the bone marrow. Until recently, the only way to obtain stem cells for transplantation was to remove a portion of the bone marrow. However, through recent medical advances, it is now possible to collect stem cells from a person's peripheral blood (that is, from the arm or another site outside the bone marrow). Today, most autologous transplants utilize peripheral blood stem cells (PBSCs). Bone marrow stem cells are more often used in allogeneic transplants, but PBSCs are beginning to be used more frequently. Collecting stem cells from bone marrow or "harvesting" bone marrow is usually done in a hospital operating room under general anesthesia. Using a needle and syringe, a surgeon will take bone marrow from several different areas of the hip bone (pelvis). The bone marrow, which appears as a thick red liquid, is typically frozen and stored until high-dose chemotherapy is completed. Collecting stem cells from peripheral blood or harvesting stem cells from the blood takes approximately a week and has certain advantages over collecting stem cells from bone marrow. No general anesthesia is needed for this collection method, and it often can be done in an outpatient setting so no overnight hospital stay is necessary. Because most stem cells reside in the bone marrow, it is necessary to move stem cells from the bone marrow to the bloodstream prior to their collection. This procedure is called mobilization. A commonly used mobilization technique is to administer a medication specifically designed to increase the number of stem cells in the blood. This medication is called a colony-stimulating factor, or "growth factor," and is usually injected under the skin, much like an insulin injection for diabetes. After the bone marrow or peripheral blood stem cells are collected from the patient, they are processed in the laboratory, cryopreserved (frozen), and stored until needed.
