What is allogeneic stem cell transplant?

In a stem cell transplant, healthy stem cells are placed in your body through an I.V. to help your bone marrow start to work as it should.

The transplant can use stem cells that come from your own blood or bone marrow. Or they can come from another person. When they come from another person, it's called an allogeneic stem cell transplant.

The donor may be a relative. Or they may be a complete stranger. The important thing is that the donor's immune system markers are closely matched to yours. This is more likely when the donor is your brother or sister.

Most stem cells are in your bone marrow. You also have some that circulate from your marrow into your blood. Bone marrow stem cells turn into red blood cells, white blood cells, or platelets to help your body stay healthy. If your bone marrow is damaged or destroyed, it can no longer make normal blood cells.

A stem cell transplant may be used to treat diseases that damage or destroy the bone marrow, such as non-Hodgkin lymphoma and Hodgkin lymphoma, leukemia, multiple myeloma, and aplastic anemia.

The allogeneic transplant process includes:

• Collecting stem cells from a donor. The new cells can come from the blood, bone marrow, or umbilical cord blood.
• Having chemotherapy (sometimes along with radiation) to destroy cancer cells or damaged stem cells.
• Transplanting the healthy stem cells.
• Waiting for the transplanted stem cells to produce healthy blood cells.

The success of a stem cell transplant depends on your age and general health, the type and stage of disease, and how well the donor matches. Serious problems can occur after a stem cell transplant.

The original disease may come back, or relapse, after the transplant. If relapse occurs, it can be treated with a second transplant, chemotherapy, or other treatments.

Early complications of both allogeneic and autologous transplants usually occur within 5 to 10 days. They include:

• Mouth sores.
• Hair loss.
• Bleeding, because of a severe decrease in red blood cells, white blood cells, and platelets.
• Nausea and vomiting.
• Diarrhea.
• Infection, such as pneumonia, shingles, or herpes simplex.

Other possible problems include:

• Depression.
• Infertility.
• Cataracts.
• Kidney, lung, and heart problems.
• Recurrence of the disease that the transplant was used to treat.
• Other cancers.

Serious, long-term complications of an allogeneic transplant include:

• Graft failure. The new stem cells don't work, or they work for a short time and then fail. If this occurs, the likelihood of a cure is low.
• Graft-versus-host disease (GVHD). The new stem cells attack other cells in your body. If it happens within 3 months, it is called acute GVHD. If it happens after 3 months, it is called chronic GVHD. After chronic GVHD occurs, it may take as long as 3 years to go away. GVHD affects the skin, gastrointestinal tract, and liver. It can cause death. GVHD is treated with medicine that lowers the activity of your immune system. GVHD does not occur when an identical twin is the donor.
• Veno-occlusive disease. This is a serious liver problem caused by the high dose of chemotherapy or radiation given before a transplant. Symptoms include swelling and tenderness of the liver, weight gain, jaundice, and fluid buildup in the belly.
• Infections.

A transplant from an unrelated donor is more likely to cause problems. But improvements in the way the cells are prepared and matched and in the care of the person after the transplant have helped reduce problems.

If the donated stem cells came from bone marrow or umbilical cord blood, it usually takes about 20 days for your bone marrow to start producing new blood cells. If the donated cells came from someone's blood, it may not take that long.

You may spend 4 weeks or longer in the hospital after an allogeneic stem cell transplant. About 1 out of 4 people need to be readmitted within the first 3 months because of problems from the surgery.

After you are discharged from the hospital, you will continue to see your doctor often. Because you received someone else's stem cells, you will need treatment with medicines to prevent your immune system from attacking the donor stem cells as though it were a foreign substance. You may also take medicine to help prevent the donor cells from attacking your body. Most people who don't have an immune system reaction take these medicines for 2 to 6 months.

An allogeneic stem cell transplant is a treatment for many conditions involving the blood or bone marrow, such as leukemia, lymphoma, neuroblastoma, aplastic anemia, or sickle cell disease.