Allogeneic Stem Cell Transplant

May 6, 2024 
This page was reviewed under our medical and editorial policy by Leslie Popplewell, M.D., Hematologist and Medical Director of Hematology and Blood and Bone Marrow Transplant, City of Hope Atlanta

An allogeneic transplant is a type of stem cell transplant used as a treatment option for certain types of blood cancers, also called hematologic malignancies. Since 2017, more than 8,000 allogeneic transplants have been performed each year in the United States, according to the Center for International Blood and Marrow Transplant Research (CIBMTR).

This guide to the allogeneic transplant process is designed to help patients and their families learn more about the treatment.

What Is an Allogeneic Stem Cell Transplant?

An allogeneic stem cell transplant may be used to help treat certain cancer types, including:

• Leukemia (most commonly acute myeloid leukemia and acute lymphocytic leukemia)
• Lymphoma
• Myeloma

It is also used to treat non-cancerous diseases that may impact bone marrow, a soft tissue in the center of bones that contains stem cells.

Stem cells are a type of cell that may reproduce and change into other types of cells, depending on the body’s needs. Stem cells can also be found in umbilical cord blood, and in some cases, cord blood may be used for a stem cell transplant.

In an allogeneic stem cell transplant, stem cells come from another person, called the stem cell or bone marrow transplant donor, who may or may not be a relative of the patient. The donor stem cells are infused into the patient. When successful, the new cells will reproduce and create healthy stem cells in the body.

To learn more about the Allogeneic Transplant process, please read the BMT Allogeneic Transplant Guide for Patients and Caregivers.

Allogeneic Stem Cell Transplant Success Rate

The outcomes of an allogeneic transplant depend on many factors, including the type of cancer, the patient’s overall health and the degree of match between the patient and donor. While every patient’s circumstances are unique, treatment outcomes and bone marrow transplant success rates are continuously improving.

Patients should talk to the care team about their prognosis based on their specific cancer type, overall health and other factors.

Allogeneic vs. Autologous

An allogeneic transplant differs from an autologous transplant. In an autologous transplant, the stem cells come from the patient, while in an allogeneic transplant, the stem cells come from a donor.

Before an allogeneic transplant, a suitable stem cell or bone marrow transplant donor — someone with a match to the patient’s human leukocyte antigen (HLA) system — must be located. HLA are proteins found in most cells of the body, and they recognize the cells that belong in the body and those that don’t. A close HLA match between the donor and patient lowers the chance of the patient’s immune system rejecting the donated cells.

A family member, particularly a brother or sister, may often be a match, so a patient’s doctor will start by looking within the family. A match may also come from an unrelated person who’s part of the national donor registry, known as the National Marrow Donor Program® (NMDP). If a match comes from an unrelated donor, this is called a matched unrelated donor (MUD) transplant.

How the Allogeneic Transplant Process Works

During the allogeneic transplant process, donor cells are collected from the donor. The donor cells are then given fresh or are stored frozen until it’s time for the infusion. A patient may expect the following preparation and process for the stem cell or bone marrow transplant procedure:

• Before the infusion, the patient is given a high dosage of chemotherapy, radiation therapy or both, known as conditioning therapy.
• The conditioning process helps destroy cancer cells, but it may also cause side effects.
• As each patient’s treatment is personalized to his or her needs, the care team will let the patient know what to expect during and after conditioning.
• After conditioning, the infusion process begins. The donor cells are thawed and infused into a vein, similar to a blood transfusion.
• Once infused into the bloodstream, the cells travel to the bone marrow and should begin reproducing to create new, healthy cells via a process called engraftment.
• Following the procedure, patients remain under close medical care and undergo regular tests and monitoring for any side effects.

The patient’s care team is available throughout the process to provide support and answer questions.

Allogeneic Transplant Recovery

The allogeneic transplant recovery process is lengthy and typically includes:

• A hospital stay that may be four weeks or longer
• A course of medication for about two to six months to help prevent the body’s immune system from attacking the stem cells from the donor
• Antibiotics to help prevent infection, as patients will have low blood cell and platelet counts during the recovery period
• Newly transplanted cells begin to reproduce and make new cells within the body in about two to six weeks post-transplant (engraftment)
• Regular follow-up visits and testing with the medical team, with visits occurring daily or weekly and blood tests, physical exams and other lab work performed as needed

Risks of Allogeneic Stem Cell Transplantation

An allogeneic stem cell transplant, like any medical procedure, carries potential risks. After the procedure, two possible risks with this transplant type include infection and graft-versus-host disease (GVHD).

Infection: The risk of infection is highest for the first few weeks following the transplant.

Transplant patients are given chemotherapy, and possibly radiation therapy, prior to the transplant. While chemotherapy and radiation therapy may help prevent the body’s immune system from destroying the new donor cells, they also weaken the immune system by lowering white blood cell counts. Patients may also need to take anti-rejection medication so that their body doesn’t reject the transplanted cells from the donor, which also weakens the immune system.

These factors make it much harder for the body to fight off infections, so patients may have an increased risk of infection while their white blood cell count is low and the immune system is weakened. After transplantation, the patient must repeat childhood vaccinations to reeducate the new cells.

GVHD: This disease is only associated with allogeneic transplants. It occurs when the newly donated cells attack the patient’s body, which may cause inflammation. GVHD may even occur in patients who have had an exact genetic match. The care team may give a patient medication to help prevent GVHD.

GVHD may be acute or chronic, both of which may range from mild to severe — and, in some cases, it may be life-threatening. If a patient experiences GVHD, the care team may prescribe medications to treat the condition.

Beyond infection and GVHD, other long-term side effects are possible following allogeneic transplants, some of which may include:

• Early menopause in women
• Infertility in both men and women
• Thyroid problems
• Bone or lung damage
• Cataracts

If patients notice any unexpected changes to their body or have any questions, they should consult their doctor.