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(Note: This information is about treating acute lymphocytic leukemia (ALL) in adults. To learn about ALL in children, see Leukemia in Children.)

Standard doses of chemotherapy (chemo) aren’t always able to cure acute lymphocytic leukemia (ALL). Even though higher doses of chemo drugs might be more effective, they can't be given because they could severely damage the bone marrow, which is where new blood cells are formed. This could lead to life-threatening infections, bleeding, and other problems due to low blood cell counts.

A stem cell transplant (SCT) allows doctors to use higher doses of chemo (sometimes along with radiation) to kill the cancer cells. After these treatments are finished, the patient gets an infusion (transplant) of blood-forming stem cells to restore their bone marrow.

Blood-forming stem cells used for a transplant are obtained either from the blood, from the bone marrow, or from a baby's umbilical cord blood. Most often, stem cells from the blood are used.

Types of stem cell transplants

The main types of stem cell transplants are:

• Allogeneic stem cell transplant, in which the stem cells come from someone else. This is the preferred type of transplant when treating ALL.
• Autologous stem cell transplant, in which the patient gets back their own cells

Allogeneic transplant: A donor’s tissue type (also known as the HLA type) needs to closely match the patient’s tissue type to help prevent the risk of major problems with the transplant. The best donor is often a close relative, such as a brother or sister, if they have the same tissue type as the patient. If there are no siblings with a good match, the cells may come from an HLA-matched, unrelated donor – a stranger who has volunteered to donate their cells. Some patients cannot have this kind of transplant because a matching donor isn’t available.

The use of allogeneic transplant is also limited by its side effects, which are often too severe for people who are older or who have other health problems. One option that may help patients who can’t have an allogeneic transplant because of age or health issues is to use lower doses of chemo and radiation that don’t completely destroy the cells in their bone marrow. This is known as a non-myeloablative or reduced-intensity transplant. This kind of SCT relies on the donor cells to kill the leukemia cells, instead of the chemo and radiation. This is not a standard treatment for ALL, and is being studied to determine how useful it may be.

Autologous transplant: A patient’s own stem cells are removed from their bone marrow or blood. They are frozen and stored while the person gets treatment (high-dose chemotherapy and/or radiation). A process called purging may be used in the lab to try to remove any leukemia cells in the samples. The stem cells are then put back (reinfused) into the patient’s blood after treatment.

An autologous transplant may be an option for patients who can’t have an allogeneic transplant because they don’t have a matched donor, or for some other reason. One problem with autologous transplants is that leukemia is a disease of the bone marrow and blood, so even after purging, there is a danger of giving the patient back leukemia cells with the stem cells.

Another reason that allogeneic transplants are preferred is because of the graft-versus-leukemia effect. When the donor immune cells are infused into the body, they may recognize any remaining leukemia cells as being foreign to them and attack them. This effect doesn’t happen with an autologous SCT.

Practical points

A stem cell transplant is an intensive and complex treatment that can cause life-threatening side effects. If your doctor thinks you might benefit from a transplant, you should discuss what kind you will have, the possible side effects, and how long it may take for you to recover. Stem cell transplants should be done at a hospital where the staff has experience with the procedure and with managing the recovery phase.