Stem cell transplant
A stem cell transplant (often also called a “bone marrow transplant”) is one of the most intensive treatments for leukemia. It makes it possible to replace diseased bone marrow with healthy blood-forming stem cells and to fight any remaining leukemia with the donor’s immune system. This topic explains in plain language the types of transplant, how a donor is chosen, the stages of the process and the possible complications.
01Short answer
02Simple explanation
The bone marrow is the “factory” for blood cells. In leukemia, this factory makes diseased cells. In a transplant, the factory is first “cleared” with strong treatment, and then new, healthy stem cells, like new seeds, are planted there.
In an allogeneic transplant, the stem cells come from a donor. In an autologous transplant, the person’s own cells are collected and stored in advance. In leukemia, allogeneic transplants are mostly used.
The donor’s cells need to match the patient’s tissue type, called HLA, a kind of “immune ID card”, as closely as possible. For this, blood or a cheek swab is taken from both the patient and the donor.
Stem cells are not given by surgery but as a drip into a vein, like an ordinary blood transfusion. They find their own way through the bloodstream to the bone marrow and, a few weeks later, start making new blood cells.
The donor’s immune cells can recognise remaining leukemia cells as “foreign” and destroy them. But sometimes they also attack the patient’s healthy tissues; this is called graft-versus-host disease.
03Scientific explanation
Types and purpose: according to NCI, a stem cell transplant restores blood-forming stem cells destroyed by high-dose treatment. According to the American Cancer Society, in an allogeneic transplant the cells come from a donor, and its main advantage is the “graft-versus-leukemia” effect. In a reduced-intensity (“mini”) transplant, the preparatory treatment is milder and the treatment relies more on the donor’s immune effect; this may be an option for older people or those with other illnesses.
Donors: according to the American Cancer Society, each full brother or sister has about a 1 in 4 chance of being a full match. If there is no matched sibling, registries are searched for an unrelated volunteer. Half-matched (haploidentical) family members, such as parents, children or siblings, and umbilical cord blood are also used. Stem cells are most often collected from the blood (by apheresis), and sometimes from the hip bone under anaesthetic.
Who is it recommended for? The 2022 EBMT recommendations classify transplant indications by disease and stage: for example, AML with intermediate or adverse genetic risk in first remission, relapsed or high-risk ALL, and CML that is not responding to treatment. According to NCI, in AML this decision is made after remission is reached, taking into account the risk group and the person’s general condition.
Complications: according to the American Cancer Society, the main risks are serious infections, bleeding, organ damage, graft failure and graft-versus-host disease (GVHD). Acute GVHD usually affects the skin, gut and liver; according to a 2017 review, chronic GVHD is one of the main causes of long-term illness and reduced quality of life after transplant and can involve the eyes, mouth, skin, lungs and other organs.
04What happens in the body?
Preparation and conditioning
Before the transplant, the heart, lungs, kidneys and any infections are checked, and a central venous catheter is placed. Conditioning treatment is then given over several days: strong chemotherapy, sometimes combined with total body irradiation. Its aim is to destroy remaining leukemia and to prepare the immune system to accept the donor cells.
How is a donor found?
Full brothers and sisters are tested for their HLA type first. If there is no matched relative, national and international donor registries are searched. The search can take weeks, so for people who may need a transplant it is often started early in treatment. Donation is voluntary, and donors usually recover fully.
Engraftment
After the infusion, blood counts are very low, and during this time the person usually stays in hospital in a room protected against infection. When the new cells settle in the bone marrow and start making blood, which is called engraftment, neutrophils and platelets gradually rise. This usually takes a few weeks; until then, blood transfusions and anti-infection medicines are given.
After going home
Even after leaving hospital, frequent check-ups are needed in the first months, so some people stay near the centre. Full recovery of the immune system can take a year or more. During this time it is important to protect yourself from infection, take medicines correctly and report signs of GVHD promptly. Childhood vaccines are usually given again later.
When to call straight away
Tell your transplant team straight away about fever, chills, a new skin rash, diarrhea, yellowing of the skin or eyes, shortness of breath, cough, bleeding or sudden weakness. After a transplant, infections and GVHD can develop quickly, and early treatment improves the outcome.
05How is a transplant done?
Four steps from the donor search to new blood.
06Types of transplant and stem cell sources (simplified)
| Type or source | What it is | Note |
|---|---|---|
| Allogeneic | Stem cells from a donor | Used most often in leukemia; has a graft-versus-leukemia effect |
| Autologous | The person’s own cells, collected in advance | Rare in leukemia; more common in myeloma and lymphoma |
| Sibling donor | A fully HLA-matched brother or sister | About a 1 in 4 chance for each sibling |
| Unrelated donor | A volunteer from a donor registry | The search can take weeks |
| Haploidentical donor | A half-matched family member | Greatly widens the chance of finding a donor |
| Cord blood | Stem cells stored after a birth | Less strict matching, but engraftment may be slower |
* Whether a transplant is needed, which type and when is decided only by the hematology and transplant team.
07Key terms
- Stem cell
- An early cell that can give rise to all blood cells.
- Allogeneic transplant
- A transplant of stem cells from a donor.
- Autologous transplant
- Giving back a person’s own stem cells.
- HLA
- Tissue-type proteins the immune system uses to recognise “self”.
- Haploidentical
- A half-matched donor, such as a parent or child.
- Conditioning
- Strong chemotherapy or radiation given before a transplant.
- Apheresis
- Collecting stem cells from the blood with a machine.
- Engraftment
- When new stem cells start making blood in the bone marrow.
- GVHD
- Graft-versus-host disease: donor cells attacking healthy tissues.
- Graft-versus-leukemia
- Donor immune cells destroying remaining leukemia.
08Key points
- A transplant replaces diseased bone marrow with healthy stem cells.
- In leukemia, transplants from a donor (allogeneic) are mostly used.
- The donor is chosen by HLA type.
- Stem cells are given as a drip into a vein.
- Engraftment of the new cells takes a few weeks.
- Donor immune cells fight the leukemia.
- GVHD and infections are the main risks.
- The team decides by weighing benefits and risks.
09Frequently asked questions
Is a transplant an operation?
No. Stem cells are given as a drip, like a blood transfusion, usually through a central venous catheter. The hard parts are the strong treatment before it and the recovery period afterwards.
Does everyone with leukemia need a transplant?
No. Many people do well with chemotherapy, targeted or immune treatment. A transplant is usually offered when the risk of relapse is high or when the leukemia has come back.
What happens if my brother is not a match?
This happens often. The team then looks for an unrelated donor in a registry, a half-matched family member or cord blood. Thanks to these options, a donor can be found for many people today.
How long will I stay in hospital after a transplant?
It depends on the type of transplant and on recovery, but usually several weeks. Even after going home, frequent check-ups are needed in the first months.
Will my blood group change?
Yes, it may. If the donor’s blood group is different, your blood group can become the donor’s over time. This does not stop the transplant from succeeding; it is simply taken into account for transfusions.
Is being a donor dangerous?
Donors are checked beforehand and the risks are usually small. Collecting from the blood may cause bone aches for a few days, and collecting bone marrow is done under anaesthetic. Donors usually recover fully within a short time.
10Questions for your doctor
Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.
Is a stem cell transplant planned for me, and why?
How is a donor found, and should my family be tested?
How long will I stay in hospital before and after the transplant?
What are the main risks of a transplant and how long is recovery?
12Sources
- National Cancer Institute (NCI). Stem Cell and Bone Marrow Transplants for Cancer
- National Cancer Institute (NCI). Acute Myeloid Leukemia Treatment (PDQ®) — Patient Version
- American Cancer Society. Stem Cell or Bone Marrow Transplant
- American Cancer Society. Types of Stem Cell or Bone Marrow Transplant
- American Cancer Society. Getting a Stem Cell or Bone Marrow Transplant
- American Cancer Society. Stem Cell Transplant Side Effects
- American Cancer Society. Donating Stem Cells or Bone Marrow
- American Cancer Society. Stem Cell Transplant for Acute Lymphocytic Leukemia
- NHS (UK). Stem cell or bone marrow transplants
- Cancer Research UK. Stem cell and bone marrow transplants
- MedlinePlus (U.S. National Library of Medicine). Bone marrow transplant
- NMDP. What is a Bone Marrow or Blood Stem Cell Transplant
- Bone Marrow Transplantation, 2022. Indications for haematopoietic cell transplantation for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2022
- New England Journal of Medicine, 2017. Pathophysiology of Chronic Graft-versus-Host Disease and Therapeutic Targets