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Allogeneic stem cell transplant

In an allogeneic transplant, stem cells are collected from a matching donor and transplanted into the patient to suppress the disease and restore the patient’s immune system. An allogeneic stem cell transplant is different from an autologous stem cell transplant, which uses stem cells from the patient's own body.

Finding a matching donor is key to a successful allogeneic stem cell transplant. A donor is often a brother, sister or other relative. In many cases, donor registries are used to find the appropriate match, through tissue typing. Tissue typing uses proteins called human leukocyte antigens (HLA), which are found on white blood cells and tissues, to determine whether a donor’s stem cells are the right match. Through an HLA test, pathologists compare the patient’s blood and tissue type against a donor’s blood samples.

Donors may include:

In addition to using stem cells from a donor’s circulating blood, stem cells from umbilical cord blood (cord blood transplant) may also be used. Stem cells in umbilical cord blood are less mature, meaning they have the potential to differentiate into various types of cells. And since the cells are frozen at birth, they have avoided environmental damage and aging. Therefore, cord blood transplants generally don’t require an extremely compatible tissue type and may help to reduce the risk of complications.

Before an allogeneic stem cell transplant, the patient undergoes a conditioning regimen, which typically involves intensive treatment—high doses of chemotherapy and radiation therapy, for example—to destroy as many cancer cells as possible.

Afterward, the patient is ready for the transplant, which typically occurs about two days after completing the conditioning regime. Much like a blood transfusion, the donated stem cells are delivered intravenously. The procedure takes about an hour.

After entering the bloodstream, the stem cells travel to the bone marrow and begin to produce new blood cells in a process known as engraftment. The transplant restores the supply of normal cells that have been destroyed by the intensive therapies.

In some cases, a mini-transplant may be recommended. A mini-transplant is an allogeneic transplant that uses lower, less toxic doses of chemotherapy and/or total body irradiation (TBI) before the transplant procedure. Using low doses of anticancer drugs and TBI eliminates some, but not all, of the patient’s bone marrow. It also suppresses the patient's immune system to prevent rejection of the transplant.

Once the bone marrow cells from the donor begin to engraft, they may cause a "graft versus tumor effect" and may work to destroy the cancer cells that were not eliminated by the anticancer drugs and/or TBI. To boost the graft versus tumor effect, patents may be given an injection of the donor's lymphocytes (immune cells). This is called a donor lymphocyte infusion.

After the transplant, your hematology oncology team will collaborate to reduce the risk of complications and address your needs throughout the stem cell transplant process.

Because it takes time to rebuild the immune system following a transplant, doctors will monitor you closely in the months following the transplant. Sometimes, the high doses of chemotherapy and radiation received before the stem cell transplant may cause side effects, such as infection. Your blood counts will be checked frequently and, if needed, you may receive a blood transfusion to prevent or treat infections and/or bleeding issues.

An allogeneic stem cell transplant also carries the risk of a complication known as graft-versus-host-disease (GVHD), a condition where the donated cells attack the tissues. The lesser the tissue type match between patient and donor, the greater the risk of GVHD. Certain drugs may be prescribed to reduce the risk of infection or GVHD.