The Basics of Bone Marrow Transplant
Rocky Mountain Blood and Marrow Transplant Program provide you a basic understanding of stem cells and their function will help you navigate the complex transplant process.
What are Stem Cells?
Stem Cells are immature blood cells that can develop into red blood cells, white blood cells, and platelets. These blood cells are essential to life: red blood cells carry oxygen from your lungs to the rest of your body, including all your organs, and return carbon dioxide to the lungs to be exhaled; white blood cells prevent and fight infections; and platelets help the blood clot and prevent excessive bleeding. Stem cells are mainly concentrated in your bone marrow space in bones like the hips, sternum and skull. However, stem cells can also be found in the blood that circulates throughout your body (peripheral blood).
Stem Cell Maturation
Your bone marrow produces stem cells that are the basic blood forming cells. These stem cells mature into either myeloid or lymphoid stem cells. Myeloid stem cells then further develop into neutrophils and monocytes (types of white blood cells), as well as red blood cells and platelets. Lymphoid stem cells divide into either T-cells or B-cells, which are important for the body’s immune response.
There are three different types of stem cell transplants: autologous, allogeneic, and syngeneic.
Autologous Transplants utilize a patient’s own stem cells. Prior to transplant, chemotherapy is given in doses 5 to 10 times higher than standard regimens with the goal of maximizing tumor death. The primary problem with higher doses of chemotherapy is the complication of irreversible damage to the bone marrow. In order to prevent this risk, stem cells are collected, frozen, stored, and then given back after completing high-dose chemotherapy. This is called a “stem cell rescue.” The stem cells will return to the marrow space and, in approximately 10-12 days, will begin to produce white blood cells, platelets and red blood cells.
Allogeneic Transplants utilize someone else’s stem cells. The donor may or may not be related to the patient. Stem cells may also be obtained from umbilical cord blood. For information about the responsibilities and procedures required of a stem cell donor, click on the following links: Planning: Donor of Stem Cells, Pre Transplant: Mobilization and Stem Cell Collection.
There are two types of allogeneic transplant conditioning regimens given prior to transplant: ablative and reduced intensity.
- Ablative Transplant — also known as "full dose" or "standard" allogeneic transplant. The patient undergoes several days of high-dose chemotherapy and possibly radiation.
This is known as the conditioning regimen. The donor stem cells are then infused into the patient. This type of transplant serves three purposes: first, it destroys diseased cells, second, it suppresses the immune system to prevent rejection of the donor’s healthy stem cells, and third, it creates a graft versus malignancy effect.
The graft (donor cells) recognizes the cancer (malignancy) as foreign and attacks it. This ablative therapy is typically given to patients with a highly aggressive disease process.
- Reduced Intensity — also known as non-ablative or “mini” transplants. Lower doses of chemotherapy and possibly radiation are used as the conditioning regimen, followed by the infusion of donor stem cells.
In this type of transplant, the purpose is not to replace the patients destroyed marrow cells, as the patient‘s marrow function would return to normal if donor cells were not administered. The conditioning regimen is given to suppress the patient’s marrow function for a short time period allowing the donor cells to grow.
The donor cells are given in order to create a graft-versus-malignancy effect. The term “mini” transplant, however, is somewhat misleading.
Although patients receive less toxic dosages of chemotherapy and radiation, and may feel well early in the post transplant process, they are still at risk to develop serious and potentially life-threatening side effects. These side effects often begin 30-60 days post-transplant when the new immune system is gaining strength.
- Donor Lymphocyte Infusion (DLI) — Although a DLI is not a transplant, it is a therapy where additional donor cells can be given to patients that have relapsed or have persistent disease.
The donor cells have been found to have potent disease killing capability and can help patients achieve remission by inducing the “graft vs. malignancy” effect.
Syngeneic Transplants utilize stem cells from an identical twin. This is considered an autologous transplant.
Your transplant physician will discuss with you the treatment options that are best suited for your diagnosis. If you are unclear about the transplant type your physician has chosen for you, please contact your transplant coordinator. The coordinator can discuss the type of transplant you are to receive or can schedule an appointment for you with your transplant physician to review your treatment plan.