What is an Allogeneic Stem Cell Transplant?

A stem cell transplant is a medical procedure in which unspecialized cells from sources such as bone marrow, placenta or the umbilical cord are introduced into a patient's body to promote healing. An allogeneic stem cell transplant procedure uses stem cells from a related or non-related donor to treat life threatening medical conditions such as certain cancers, blood and auto-immune diseases. Stem cells are harvested from a genetically compatible donor whose tissue closely matches the patient's tissue to help reduce the chances of developing graft-versus-host-disease (GVHD).

An allogeneic stem cell transplant is used to treat some cancers, such as multiple myeloma, leukemia and lymphoma. Non-cancerous medical conditions that may require a stem cell transplant are severe forms of systemic lupus erythematosus (SLE), thalassemia, aplastic and sickle-cell anemia. In each of the aforementioned conditions, the body's ability to produce healthy blood cells and regulate normal immune system function is greatly diminished or destroyed.

Before an allogeneic stem cell transplant can occur, the patient must be matched with a donor and must complete a treatment regimen to prepare for the transplant. The first step in this process is matching human leukocyte antigens (HLA) between donor and recipient. Ensuring HLA compatibility is vital for preventing GVHD and rejection of the donor's stem cells.

Patients must also undergo either a conditioning myeloablative or non-myeloablative regimen prior to the transplant procedure. Myeloablative conditioning uses a combination of high dose radiation and drugs to destroy the diseased bone marrow cells. The much newer and less risky non-myeloablative regimen, on the other hand, uses a much lower dose of drugs and radiation to kill most of the bone marrow cells. Immunosuppressant drugs are also given to transplant recipients to help prevent rejection of donor cells. The type of conditioning regimen used will largely depend on the patient's age, type of medical condition, overall health and compatibility with the HLA donor.

Once conditioning has been completed, the process of allogeneic stem cell transplantation can begin. Traditionally, stem cells have been harvested from the donor’s bone marrow; however, the peripheral transplantation method is gaining popularity. In peripheral transplantation, blood cells are removed from the donor’s arm, placenta or umbilical cord and filtered through a special machine that removes white blood cells. Along with granulocyte colony-stimulating factor hormone (GCSF), the white blood cells from the donor are injected into the recipient to stimulate healthy stem cell production.

While an allogeneic stem cell transplant can be life saving for many, the procedure is not without risks and complications. Serious side effects include infections, secondary cancers, GVHD and graft failure. In the case of GVHD, the donor's transplanted cells attack the recipient's tissue, causing organ damage and death. Less serious side effects of the procedure include hair loss, fatigue, and infertility. Successful management and prevention of complications such as GVHD can be vital to the patient's long-term survival.