Allogeneic Stem Cell Transplantation

Allogeneic stem cell transplantation is a medical procedure that uses healthy stem cells from a donor to replace damaged or diseased bone marrow, offering hope for patients with blood cancers, blood disorders, and immune system conditions.

Table of contents

• What is Allogeneic Stem Cell Transplantation?
• Conditions Treated
• Finding a Donor
• Preparing for the Transplant
• The Transplant Procedure
• Recovery and Life After Transplant
• Possible Complications

allogeneic bone marrow transplant, allogeneic HSCT, donor stem cell transplant

What is Allogeneic Stem Cell Transplantation?

An allogeneic stem cell transplant is a medical procedure that replaces unhealthy stem cells (cells in your bone marrow that create blood cells) with healthy ones from a donor^[1]. The word “allogeneic” means that the stem cells come from another person, not from your own body^[3]. About 40% of all stem cell transplants use donated stem cells^[3].

This type of transplant works differently from other cancer treatments. The donated stem cells create new, healthy blood cells in your body. These new cells can also recognize and attack cancer cells through what doctors call a graft-versus-leukemia effect or graft-versus-tumor effect^[5][10]. This means the transplant itself is the treatment for the disease, not just a way to help you recover from chemotherapy^[5].

The blood stem cells used in an allogeneic transplant can be collected in three different ways: from the donor’s blood, from the bone marrow inside the donor’s hipbone, or from the blood of a donated umbilical cord^[1].

Conditions Treated

Allogeneic stem cell transplantation is used to treat several serious conditions affecting the blood, bone marrow, and immune system^[3]. Healthcare providers typically recommend this transplant when other treatments don’t work or when a condition comes back after treatment.

The procedure can treat several types of conditions, including:

• Acute lymphoblastic leukemia (ALL)
• Acute myeloid leukemia (AML)
• Aplastic anemia
• Lymphoma
• Myelodysplastic syndrome
• Myeloproliferative neoplasms (MPN)
• Sickle cell disease

For some of these conditions, allogeneic stem cell transplantation may offer the possibility of a cure^[3].

Finding a Donor

Finding the right donor is a critical step in the transplant process. Not everyone can be your donor. The donor needs to have a tissue type that closely matches yours^[11].

Tissue matching is based on human leukocyte antigens (HLA), which are proteins found on the surface of your white blood cells^[11]. HLA are important for your immune system because they help your body recognize your own cells and not attack them. If foreign cells enter your body, your white blood cells see them as different and try to get rid of them.

The best match is most often a brother or sister. Family members will have a blood test to check their tissue type^[11]. The person whose tissue type is most like yours is chosen to be the donor.

If no family member is a close match, your doctor will help you search for an unrelated donor through a donor registry, cord blood banks, or both^[11]. The National Marrow Donor Program has millions of people registered who have had their blood typed for this purpose. However, searching for an unrelated donor may take weeks or even months to complete^[11].

Preparing for the Transplant

Before your transplant, your medical team will perform several tests to make sure you can manage the side effects of the treatment^[3]. These tests may include:

• A complete blood count (CBC) to check your red blood cells, white blood cells, and platelets
• An echocardiogram to see how well your heart pumps
• An electrocardiogram (EKG) to check your heart’s rhythm
• Liver function or kidney function tests

If you have cancer, your team may also do a bone marrow biopsy to remove a small sample of your bone marrow^[3]. A medical specialist will examine your bone marrow cells for any new changes. The results help your team understand the risk that your condition could come back after the transplant.

The next important step is called pre-transplant conditioning. This treatment uses chemotherapy, radiation therapy, or both^[1][3]. Before you receive the donor cells, you will receive high doses of these treatments to:

• Kill cancer cells in your body
• Make room in your bone marrow for new blood stem cells to grow
• Suppress your immune system to reduce the chance your body will reject the donated stem cells

You will stay in the hospital for conditioning, which typically takes one to two weeks to complete^[3].

The Transplant Procedure

The actual transplant procedure is painless^[3]. Your transplant care team will place a central venous catheter (CVC) in one of the large veins in your upper chest. The CVC is a tube that delivers the new stem cells to your bone marrow.

The infusion process is similar to receiving a blood transfusion. Healthy stem cells flow from a bag through the CVC into your bone marrow^[3]. The infusion typically takes 30 minutes to an hour. Your transplant team will be with you throughout the infusion, checking your vital signs and watching for any symptoms of side effects.

Side effects during the infusion are rare and often mild. Some common potential side effects include chills, feeling short of breath, and fever^[3].

Recovery and Life After Transplant

After your transplant, you will stay in or close to the hospital so your transplant care team can watch your recovery closely^[3]. Recovery from an allogeneic stem cell transplant takes time. It can be as long as a year before you really feel you are on the road to recovery^[18].

When you leave the hospital, your central line usually stays in for a little while^[18]. Your nurse can use it for blood tests at follow-up appointments. You will have regular appointments with a nurse to clean and flush your central line, or you may be given instructions on how to care for it yourself.

You will need to take special precautions to protect yourself from infections because your immune system will be weak after the transplant^[18][19]. During the first 100 days after your transplant, you should:

• Limit the number of visitors to your home
• Avoid close contact with anyone who is not feeling well or who has a respiratory illness
• Avoid crowded public places like cinemas or public transport during peak times
• Stay away from anyone with an infection or anyone who has had contact with someone with chicken pox or measles

Your home will need to be kept very clean, but you should not do the cleaning yourself^[19]. You should not be in a room when it is being cleaned, and you should wait at least 30 minutes before entering a room that has just been cleaned.

Your diet may also need to change temporarily to reduce the risk of infection from food^[18]. Your medical team will give you specific advice about what foods to eat and avoid.

You won’t be able to return to normal daily activities like work, school, or college until your white blood cell levels are almost normal^[18]. This usually takes around 3 to 6 months. When you do return, it’s a good idea to start part-time until you have regained some of your strength.

Physical activity is important and can help reduce tiredness after treatment^[18]. How much you can do will depend on how fit you are and how you feel. Gentle walking is suitable for most people to start with. Listen to your body and build up slowly.

Possible Complications

Allogeneic stem cell transplants can result in a condition called graft-versus-host disease (GVHD)^[3][10]. This happens when the donated stem cells attack other cells in your body. GVHD is common after transplant and often limits the success of treatment^[10].

You are also at increased risk of getting infections after your transplant. It’s likely that you will get at least one infection that requires you to stay in the hospital again^[18]. This can be upsetting if you haven’t been home for long, but it’s important to let your team know if you are struggling to cope. Support and help are available.

Despite these challenges, allogeneic stem cell transplantation remains one of the most effective treatments for many blood cancers, blood disorders, and immune system conditions. Your healthcare team will work closely with you to manage any complications and support your recovery.