Also known as Allogeneic Hematopoietic Cell Transplant, Allogeneic HCT or Allogeneic BMT.
An allogeneic stem cell transplant uses a donor's healthy blood-forming cells. Stem cells are made in the spongy part of bones, called bone marrow. They make all types of blood cells in your child’s body.
What is an allogeneic transplant?
An allogeneic transplant replaces a patient’s (recipient) damaged or destroyed blood-forming cells (stem cells) with healthy cells from another person. This person is called a donor. Donor cells may come from a donor's blood, bone marrow, or donated umbilical cord blood.
The donor stem cells travel to your child's bone marrow. They grow and make healthy blood cells, including red blood cells, platelets, andwhite blood cells.
The first step in allogeneic transplant is to find a person who can donate healthy stem cells. The transplant team will help with the donor search to find a matched donor. Donor matching means finding a donor whose cells are like your child's. This is known as an HLA match.
HLA matching: HLA stands for human leukocyte antigen. Human leukocyte antigens are protein markers on the surface of most cells. They help the immune system know what belongs in the body and what does not. If the donor cells are not well-matched to your child's HLA type, your child's cells and the donor cells may attack each other. This can lead to problems, such as graft rejection or graft-versus-host disease (GVHD).
The donor can be a relative or someone not related to your child.
Since HLA markers are inherited from parents, a biological brother or sister may be the best match if they inherited the same HLA from their parents that the patient did. A biological parent will be a half match for the patient.
If no relatives are a good match, the cells may come from a volunteer donor who matches well with your child. Unrelated donors are found through the Be the Match Registry of the National Marrow Donor Program.
Doctors will also review the donor's health and medical history to ensure they are an appropriate donor.
There are 3 different types of HLA matches for a transplant:
Full match: The patient and the donor have the same HLA markers. This is the best match, but it can be hard to find.
Partial match (mismatched): The donor matches most, but not all, of the patient’s HLA markers.
Haploidentical match (half match): If the patient and the donor share half of the same HLA markers, this is a haploidentical or “haplo” match. Biological parents are a half match for their child.
A better-matched donor is preferred to improve the chance for a successful transplant and lower the risk of complications. However, with advances in transplant methods, mismatched donor transplants are fairly common, and many are successful.
Your child and potential donors will be asked to provide a blood sample or cheek swab to get cells for HLA typing. After the donor is found, the stem cells will be collected from the donor and prepared for the transplant.
Pre-transplant testing and evaluation
Your child will be evaluated by their care team before the transplant. Getting a transplant and recovering from it is physically and emotionally challenging.
The medical team will do tests to make sure your child is ready for a transplant. Your care team will consider factors such as:
Your child’s diagnosis
Your child's age
Medical history and health of your child's heart, lungs, and other organs
Past treatments
If there is a suitable donor
Pre-transplant tests may include a complete medical exam, blood tests, and imaging studies, such as CT, MRI, or X-rays.
Your child will also have a central line for chemotherapy and medications during the transplant process.
To prepare for transplant, your child will go through a process called conditioning, or the preparative regimen. Conditioning increases the chance that the transplant will be successful. Conditioning lasts about 1-2 weeks.
Radiation therapy such as total lymphatic irradiation (TLI) or total body irradiation (TBI).
Antibody therapy to weaken the patient's immune system so your child's body does not reject the new donor cells and reduce the risk of graft versus host disease (GVHD).
The goal of conditioning is to:
Make room in the bone marrow for new donor cells to grow
Lower the body's immune response to help the immune system accept the new donor cells
Kill any abnormal blood forming cells left in the body
The transplant team will watch for side effects. Your child may receive treatments to help prevent or manage them.
Infusion of stem cells
After conditioning, the donor cells are given to your child by an infusion into the bloodstream. This is similar to getting a blood transfusion. Donor cells are in a bag or syringe that is connected through a tube to your child's central line. Your child is awake during the infusion. It only takes a few minutes to a few hours, and it is not painful.
Your child will receive the donor stem cells by infusion. The stem cells travel through the bloodstream to the bone marrow where they begin to make healthy red blood cells, white blood cells, and platelets.
Engraftment
The goal of allogeneic transplant is for the donor's blood-forming stem cells to travel to the bone marrow and begin to make more stem cells. The stem cells become white blood cells, red blood cells, and platelets. This is called engraftment.
Engraftment generally takes 2-4 weeks, but the time can vary. Neutrophils (a type of white blood cell that fights infection) grow and engraft first, followed by platelets and then red blood cells. Your child may get medicines to help with engraftment.
During this time, your child will have regular blood tests, such as a complete blood count (CBC) test, to check the number of red blood cells, white blood cells, and platelets. A bone marrow aspiration and biopsy may be done to see how well the bone marrow is making new cells.
Your child may also need to get transfusions of blood products until they can make enough of their own.
Supportive care after transplant
Your child will get supportive care during the bone marrow transplant process to help manage side effects. This may include:
Transfusions of platelets and red blood cells
Medications to prevent or fight infection, such as antibiotics, anti-viral, or anti-fungal medicines
Medications to prevent nausea and vomiting
Pain medications
Nutrition support
Medications to prevent graft-versus-host disease (GVHD)
Side effects may vary. Some patients have few side effects, while others may have serious complications that result in long hospital stays. Some problems can even be life-threatening.
Side effects that may occur soon after allogeneic transplant include:
Side effects from chemotherapy or radiation therapy used during conditioning or as part of treatment
Infection because of a low white blood cell count (neutropenia)
Weakness or fatigue caused by fewer red blood cells (anemia)
Increased risk of bleeding or bruising caused by low platelets (thrombocytopenia)
Graft failure or rejection if the cells do not grow well or are destroyed
Problems with the heart, lung, kidneys, liver, or other organs
After the new donor cells have grown, other risks include:
Graft-versus-host disease (GVHD) may occur if the donor cells see the patient's normal cells as different and attack them. Other immune system problems can also occur.
Infection is an ongoing risk for several months as the new donor cells grow and the new immune system matures.
Your child’s disease could come back (relapse) or get worse (progression) if the transplant is not successful.
Long-term or late effects may develop due to the transplant or any treatments a patient received before transplant.
Caring for your child after allogeneic transplant
Your child will stay in the hospital until neutrophil engraftment occurs. A parent or adult family member will need to stay with your child while they are in the hospital. Your child will stay in local or long-term housing for several months after hospital discharge. After discharge, your child will have regular outpatient clinic visits and lab tests several times a week to check their progress.
Your care team will teach you how to care for your child after transplant. It is good to have more than 1 family member who can be trained and available to help care for your child.
To help your child recover and stay healthy after transplant:
Take steps to prevent infection. Your child will have a very weak immune system for weeks after the transplant. Avoid public areas, wash hands often, limit visitors, stay away from people who are sick, and wear a mask as instructed.
Watch for signs of infection or illness. Contact your care team if your child develops a fever or symptoms such as rash, nausea, vomiting, diarrhea, abdominal pain, mouth sores, bruising or bleeding, trouble breathing, headache, or other change in condition.
Give medicines as instructed. Let your care team know if your child has any problems taking medicines or keeping them down.
Encourage your child to be active throughout the day if they feel well enough.
Avoid sun exposure when possible. Protect your child’s skin from the sun and use sunscreen with an SPF of 30 or higher.
Keep all medical appointments and contact your care team if you have any questions or concerns.
Questions to ask your care team
What are the benefits and risks of an allogeneic transplant for my child?
Are there any other treatment options?
How does allogeneic transplant work?
Who should be considered as a donor?
What can I expect at each stage of the transplant?
How long will my child be in the hospital, and how should I prepare for it?
What are the short-term and long-term side effects of an allogeneic bone marrow transplant?
What monitoring and follow-up care will my child need after transplant?
Key points about allogeneic transplant
An allogeneic stem cell transplant (bone marrow transplant) replaces a patient’s blood-forming stem cells with healthy stem cells from a donor.
Allogeneic transplant steps include pre-transplant testing and evaluation, conditioning, infusion, engraftment, and monitoring and follow-up care.
After the conditioning treatment, the stem cells are given to the patient through an infusion. The donor's infused stem cells travel to the patient's bone marrow and begin to make new stem cells.
It takes 2–4 weeks for new cells to start growing. This is called engraftment.
Your care team can help you know if an allogeneic transplant is a good treatment option for your child and let you know what to expect.
A stem cell transplant (bone marrow transplant) may be used as a treatment for some childhood cancers and blood disorders. Learn more about stem cell transplants.
Apheresis may be done to collect hematopoietic (blood-forming) stem cells for transplant. Learn what to expect during apheresis for stem cell collection.
