Stem Cell or Bone Marrow Transplant
A stem cell transplant is an important part of treatment for some cancers, especially certain types of leukemia, lymphoma, and multiple myeloma.
What is a stem cell transplant?
A stem cell transplant puts healthy blood stem cells back into your body after your bone marrow has been destroyed by disease, chemotherapy (chemo), or radiation. Depending on where the stem cells come from, it might also be called a:
- Bone marrow transplant (BMT)
- Peripheral blood stem cell transplant (PBSCT)
- Umbilical cord blood (UCB) transplant
All of these procedures can also be called hematopoietic stem cell transplants (HSCT).
How does a stem cell transplant work to treat cancer?
Some cancers start in the bone marrow. Other cancers can start in another part of the body and spread to the bone marrow.
When cancer is in your bone marrow, the cancer attacks it. This causes the bone marrow to make too many unhealthy cells. The unhealthy cells crowd out healthy ones, so they no longer work like they should.
For these cancers to stop growing, they need the bone marrow cells to work properly and start making new, healthy cells.
Stem cell transplants replace bone marrow cells that have been destroyed by cancer or by the chemo and/or radiation used to treat the cancer.
The goal of a stem cell transplant is to wipe out the cancer cells along with the damaged or unhealthy bone marrow cells and give a person new, healthy stem cells to “start over."
There are different kinds of stem cell transplants. In general, they all begin by giving you chemo (sometimes along with radiation) to kill cancer cells.
In a typical stem cell transplant for cancer, you first get chemo (and radiation therapy, if needed) to try to kill the cancer cells in your body. This treatment also kills the stem cells in the bone marrow. The amount of chemo and radiation you get will depend your cancer type, overall health, and other factors.
Some people may receive very high doses of chemo (and sometimes radiation) to kill all the stem cells in their body and cause your bone marrow to completely stop making blood cells for a period of time. In other words, all your original stem cells are destroyed on purpose. This is called myeloablation or myeloablative therapy.
Other people may get lower doses of chemo and radiation to kill some, but possibly not all, of their cancer cells. This is called reduced intensity conditioning (RIC).
No matter how much chemo and radiation you get, your destroyed cells need to be replaced with new, healthy stem cells. That’s where the transplant comes in.
Your body needs blood cells to function. Soon after your original stem cells are destroyed, they must be replaced by healthy blood stem cells. The replacement stem cells are put into your body (transplanted) through a vein, much like a blood transfusion.
The goal is that over time, the transplanted cells will settle in your bone marrow, where they will begin to grow and make healthy new blood cells. This is called engraftment.
- Transplanting healthy cells lets doctors use much higher doses of chemo to try to kill all the cancer cells.
- The transplanted stem cells help "rescue" your bone marrow by replacing the stem cells that were destroyed during treatment.
- The transplanted stem cells can grow into healthy, mature blood cells that work normally and make new cells that are free of cancer.
This process is used for the 2 main types of transplants, autologous and allogeneic.
One type of stem cell transplant, called an allogeneic (allo) transplant, also works in another way to treat some cancers and other diseases.
An allo transplant uses stem cells from a donor, not from the person with cancer. Donor stem cells often find and kill cancer cells better than the immune cells of the person who has the cancer.
These donor stem cells can actually kill some types of cancer cells, along with rescuing bone marrow and allowing normal blood cells to develop.
This is called the graft-versus-cancer or graft-versus-leukemia effect. (In this case, the “graft” is the donated cells.)
Chimeric antigen receptor (CAR) T-cell therapy is a way to get a specific type of immune cells in your body to fight cancer by changing them in the lab so they can find and destroy cancer cells.
The cells used for this treatment are a type of white blood cell called T cells.
CAR T-cell therapy is also sometimes talked about as a type of cell-based gene therapy, because it involves altering the genes inside T cells to help them attack the cancer.
The way CAR T-cell therapy is done has some similarities to stem cell transplant, but they are different treatments. In CAR T-cell therapy:
- White blood cells are removed from your body.
- T cells are separated and sent to the lab to be changed into CAR T cells. They are then grown and multiplied in the lab.
- When enough cells have been made, you are given chemotherapy to help get rid of some (but not all) cancer cells.
- The CAR T cells are returned to your body through an IV.
- As they travel throughout your body, the CAR T cells bind with cancer cells and start to grow and destroy them.
Deciding to have a stem cell transplant
Although a stem cell transplant can help and possibly cure some people, the decision to have a transplant isn’t easy. Like everything in your medical care, you are the one who makes the final decision about having a stem cell transplant.
Stem cell transplants have been used to cure thousands of people with cancers that did not otherwise have a promising cure. Still, there are possible risks and problems. Some of these can be life threatening. The expected risks and benefits must be weighed carefully.
Weighing the risks and benefits
Your cancer care team will compare the risks of your cancer itself to the risks of the transplant. They may also talk to you about other treatment options or clinical trials.
The stage of your cancer, the time from diagnosis to transplant, the donor type, and your age and overall health are all part of weighing the pros and cons before making this decision.
Be sure to express all your concerns and get answers you fully understand. Make sure the team knows what’s important to you. Transplant is a complex process. Find out as much as you can and plan ahead before making your choice.
Graft-versus-host disease (GVHD)
GVHD is a common risk in allogeneic (allo) transplants.
In this type of transplant, the stem cells come from another person (a donor). The donor cells that you get can be a threat to your cells, body tissues, and organs. This attack can cause damage that ranges from mild to severe.
See Stem Cell Transplant Side Effects to learn more about this.
Understanding success rates
It’s important to know the success rate of the planned transplant based on your:
- Diagnosis
- Stage in treatment
- Any other conditions that might affect you and your transplant
In general, transplants are more likely to be successful if they’re done in the early stages of disease (or in remission) and when your overall health is good. Ask about these factors and how they affect the expected outcomes of your transplant or other treatment.
Getting a second opinion
Many people get a second opinion before deciding to have a stem cell transplant. You may want to talk to your cancer care team about this, too. Also contact your health insurance company to ask if they will pay for a second opinion.
For caregivers
Being the main caregiver for someone going through stem cell transplant is an important job that lasts for months. You will get training and support from the transplant team, but you will be responsible for much of your loved one's daily care after they leave the hospital.
- If the transplant is outpatient, you will need to be with your loved one all day, every day.
- Expect to attend appointments for up to the first 100 days.
This can be overwhelming and put you at risk for anxiety and depression. It's important to talk about your feelings and ask for help.
To learn more about the role of a caregiver and how to find support, see Cancer Caregiver Resources.
Post-stem cell transplant (rehabilitation)
The process of stem cell transplant doesn’t end when you go home. You’ll feel tired, and some people have physical or mental health problems in the post-transplant period. Recovery takes months or years.
During post-transplant rehabilitation, you will:
- See your transplant team often. At first, these visits will be daily (or every other day). You'll move to less frequent visits if things go well.
- Take extra care to avoid infections. It can take 6 to 12 months, or longer, for your immune system to work well again.
- Get new vaccinations. Stem cell transplant wipes out all the vaccinations you got as a child. Post-transplant, you'll get these vaccinations again.
Learn more about post-transplant rehabilitation in Getting a Stem Cell Transplant.
- Written by
- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American Society of Clinical Oncology (ASCO). What is a stem cell transplant (bone marrow transplant)? Accessed at cancer.net. Content is no longer available.
Mousaei Ghasroldasht M, Seok J, Park HS, et al. Stem cell therapy: from idea to clinical practice. International journal of molecular sciences. 2022 Mar 5;23(5):2850. Accessed at https://doi.org/10.3390/ijms23052850 on February 27, 2025.
Negrin RS. Preparative regimens for hematopoietic cell transplantation. UpToDate. 2023. Accessed at https://www.uptodate.com/contents/preparative-regimens-for-hematopoietic-cell-transplantation on March 14, 2025.
Sieff CA. Overview of hematopoietic stem cells. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/overview-of-hematopoietic-stem-cells on February 25, 2025.
Last Revised: June 5, 2025
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