The most common bone marrow transplant procedure is the autologous bone marrow transplant. With this type of transplant, a patient serves as his or her own bone marrow donor. An autologous transplant can also be performed using the patient's peripheral blood stem cells. This option is known as an autologous peripheral blood stem cell transplant or autologous stem cell transplant. The terms bone marrow transplant and stem cell transplant are often used interchangeably.
With an autologous bone marrow transplant procedure, the patient's marrow must first be harvested. As bone marrow lies at the center of bones, the patient is sedated using general or regional anesthesia. During the surgery, a doctor inserts needles into the pelvic bone or sternum to extract the marrow. The harvested marrow is then processed to remove any blood or fragments of bone.
Unlike the autologous bone marrow transplant procedure, an autologous stem cell transplant does not involve surgery. The stem cells are harvested from the bloodstream through a process called apheresis, also known as leukapheresis. To prepare for apheresis, the patient is administered four to five days of a medication called granulocyte-colony stimulating factor (G-CSF), which stimulates the bone marrow to release more stem cells into the bloodstream. The patient's blood is then removed through a large vein in the arm or through a central veneous catheter, a tube that is inserted in a vein in the neck, chest, or groin. The patient's blood is next processed through a machine that filters out the stem cells and returns the blood to the patient.
Both harvested bone marrow and peripheral blood stem cells can be preserved and frozen, using a technique called cryopreservation. The patient then undergoes a preparative or conditioning regimen that consists of chemotherapy and, less often, radiation. The purpose of preparing for the transplant is to completely eliminate diseased cells from the patient's body. During this process, other cells are also eliminated, hopefully allowing the transplanted bone marrow or stem cells to create an improved immune system that will provide an effective treatment against the patient's disease.
During the actual autologous bone marrow transplant procedure, as well as in the autologous stem cell transplant, the harvested and processed cells are transplanted back into the patient through a central venous catheter. The cells then travel through the bloodstream and into the spaces inside the bones, where they create new bone marrow. As there is no risk of the body rejecting its own cells, the autologous transplant is considered to be safer and has become more common than allogeneic bone marrow transplants, where bone marrow or stem cells from a donor are used. Autologous bone marrow or stem cell transplants can be prescribed to treat any one of a variety of diseases, including Ewing's sarcoma, lymphoma, and certain brain tumors.