A bone marrow transplant (also called a stem cell transplant or hematopoietic stem cell transplant) is a medical procedure that infuses healthy blood-forming stem cells into the body to replace damaged or diseased bone marrow. The goal is to restore the body's ability to
produce healthy red blood cells, white blood cells, and platelets.
Why It's Done
Bone marrow transplants are used to treat a variety of cancerous and non-cancerous diseases, including:
Cancers: Leukemias (acute and chronic), lymphomas (Hodgkin's and non-Hodgkin's), and multiple myeloma.
Blood Disorders: Aplastic anemia, sickle cell anemia, and thalassemia.
Immune Deficiencies: Severe combined immunodeficiency (SCID) and Wiskott-Aldrich syndrome.
Other Conditions: Myelodysplastic syndromes (MDS), certain solid tumors (like neuroblastoma), and some inborn errors of metabolism.
The procedure can allow a patient to receive high doses of chemotherapy or radiation (which would otherwise destroy their bone marrow) and, in the
case of allogeneic transplants, can also provide a new immune system that directly attacks remaining
cancer cells (the graft-versus-tumor effect).
Types of Transplants
There are two main types of bone marrow transplants, categorized by the source of the healthy stem cells:
Autologous Transplant: The patient's own healthy stem cells are collected and stored before they undergo high-dose chemotherapy or radiation.
After treatment, the stored cells are reinfused to "rescue" the bone marrow. This has a lower risk of rejection but a potentially higher risk
of the cancer returning.
Allogeneic Transplant: The patient receives stem cells from a donor (a family member, an unrelated volunteer from a registry, or umbilical cord blood).
The donor's tissue type (HLA markers) must be a close match to minimize the risk of complications like graft-versus-host disease (GVHD),
where the new immune cells attack the recipient's body
The Procedure
The process involves several stages:
Evaluation and Preparation: The patient undergoes extensive tests to ensure they are healthy enough for the procedure. A central venous
catheter (a thin tube) is placed in a large vein for administering treatments and drawing blood.
Conditioning: The patient receives high-dose chemotherapy and/or radiation therapy to destroy existing diseased bone marrow and suppress the immune system to prevent rejection of new cells.
Transplant (Infusion): The collected healthy stem cells are infused into the patient's bloodstream through the central line, similar to a blood transfusion. This part is painless and the patient is awake.
Engraftment and Recovery: The new stem cells travel to the bone marrow, multiply, and begin producing new blood cells. This process (engraftment)
typically takes a few weeks, during which the patient is closely monitored in a protective environment due to a high risk of infection.
Full immune system recovery can take months or years.
Risks and Considerations
Bone marrow transplants carry significant risks, including infections, bleeding, organ damage, and GVHD in allogeneic transplants.
The potential benefits and risks are carefully weighed by a multidisciplinary medical team before proceeding.
