Types of Stem Cell or Bone Marrow Transplant

There are 2 main types of stem cell transplants: autologous (auto) and allogeneic (allo). They are named based on who donates the stem cells.

Autologous (auto) transplant:

• “Auto” means self.
• In an auto stem cell transplant, you are your own donor.
• Your stem cells are removed from your body and returned to you later. 

Allogeneic (allo) transplant:

• “Allo” means other.
• The stem cells in allo transplants come from another person (a donor).
• The donor could be related or unrelated to the person getting the transplant.

Within these 2 main types of transplant, there are a few other possible options. The transplant you get will depend on many factors, including the type of cancer you have.

Auto stem cell transplant

In an auto stem cell transplant, you are your own donor. This kind of transplant is mainly used to treat certain leukemias, lymphomas, and multiple myeloma. It’s sometimes used for other cancers, like testicular cancer and neuroblastoma, and certain cancers in children.

Doctors use auto transplants for other diseases too, like systemic sclerosis, multiple sclerosis (MS), Crohn's disease, and systemic lupus erythematosus (lupus).

What happens during an auto stem cell transplant?

For this type of transplant, there are a few steps to remove and return your stem cells.

Step 1: Collecting your stem cells

In this first step, your stem cells are removed (harvested). This might take several days.

First, you get injections (shots) of a medication that increases the number of your stem cells. Then your transplant team collects the stem cells through a vein in your arm or chest. The cells are stored frozen until they are needed.

You may need to repeat this step before you are ready to move on to Step 2.

Step 2: Pre-transplant treatment (conditioning)

This step takes 2 to 10 days. You will get a high dose of chemotherapy. Occasionally, people also have radiation therapy, called total body irradiation (TBI).

Step 3: Getting your stem cells back

This is your transplant day. Your transplant team puts the stem cells back into your bloodstream through your catheter. The dose of stem cells is given in an infusion. It takes about 30 minutes for each bag or syringe of stem cells to infuse. You might get more than one bag or syringe.

Step 4: Recovery

Your doctor will closely monitor the recovery and growth of your stem cells. You will take antibiotics to reduce infection, antivirals to reduce viruses, and antifungals to reduce fungal infections. Your transplant team will also treat any side effects.

You can learn more about this process in What Is It Like to Donate Stem Cells.

Benefits of auto stem cell transplant

One benefit of auto stem cell transplant is that you get your own cells back, so you don’t have to worry about your body rejecting those cells.

You also don’t have to worry about immune cells from the transplant attacking healthy cells in your body (known as graft-versus-host disease), which is a concern for allo transplants. 

Risks of auto stem cell transplant

An auto transplant graft might still fail. Failing means the transplanted stem cells don’t “take” or don’t go into the bone marrow and make blood cells like they should.

Auto transplants also don’t produce the “graft-versus-cancer” effect, in which the donor immune cells from the transplant help kill any cancer cells that remain.

Another risk of an auto transplant is that all the cancer cells might not be removed from your stem cells before they are transplanted back into your body. These cancer cells may not show up for months or even years after the transplant.

Removing cancer cells from collected stem cells (purging)

To help prevent any remaining cancer cells from being returned to your body along with the stem cells, some centers use a process called purging.

During purging, the stem cells that were removed from your body are treated before they are returned to you. Transplant centers offer different ways to purge stem cells for the best transplant outcome. Purging of stem cells is often done as part of a clinical trial.

Purging might work for some people, but there haven't been enough studies yet to know if this is really a benefit.

Possible risks of purging

A possible downside of purging is that some normal stem cells can be lost during the process.

This may cause your body to take longer to start making normal blood cells, and you might have very low and unsafe levels of white blood cells or platelets for a longer time. This could increase your risk of infections or bleeding problems.

In vivo purging

In vivo purging is another option to help kill cancer cells that might be found in your stem cells. In this case, the stem cells are not treated before they are returned to your body. Instead, you are given anti-cancer medications after the transplant.

Tandem (double auto) transplant

Doing 2 auto transplants in a row (within 6 months) is known as a tandem transplant or a double auto transplant.

What happens during a tandem transplant?

In this type of transplant, you get 2 courses of high-dose chemo as myeloablative therapy. Each course of chemo is followed by a transplant of your own stem cells.

All the stem cells needed for the transplants are collected before the first high-dose chemo treatment. Half of the collected stem cells are used for each transplant. Usually, the 2 courses of chemo are given within 6 months. You get the second course after you recover from the first.

When are tandem transplants used?

Tandem transplants have become the standard of care for certain cancers, including high-risk types of cancer such as:

• Childhood cancer: neuroblastoma
• Adult cancer: multiple myeloma

With these cancers, tandem transplants seem to show good results.

Doctors often disagree about whether a tandem transplant is better than a single transplant for treating other types of cancer. Because this treatment involves 2 transplants, the risk of serious outcomes is higher than for a single transplant.

Sometimes, an auto transplant followed by an allo transplant might also be called a tandem transplant. For more on this, see Reduced Intensity Conditioning (RIC) below.

Allo stem cell transplant

Allo stem cell transplants use donor stem cells. In the most common type of allo transplant, the stem cells come from a donor whose tissue type closely matches yours.

Family member donor: You receive stem cells from a close blood-related family member, usually a brother or sister. This is sometimes called an MRD (matched related donor) transplant.

Unrelated donor: If you don’t have a close match in your family, a donor might be found through a national registry. This is sometimes called an MUD (matched unrelated donor) transplant.

Types of allo transplant

• Matched related: Stem cells from a blood-related family member who is a full match.
• Matched unrelated: Unrelated donor whose cells are a full match.
• Mismatched unrelated (MMUD): Unrelated donor whose cells are a partial match.
• Reduced intensity conditioning transplant (RIC): Uses a smaller amount of chemo/radiation but still works to treat the cancer.
• Half-matched (haplo): Stem cells from a family member who isn’t a full match.
• Syngeneic: Stem cells from an identical twin.

Each of these types is discussed in detail below.

What happens during an allo transplant?

An allo transplant works about the same way as an auto transplant, with a few exceptions. Stem cells are collected from the donor and stored or frozen. After you get chemo and/or radiation as your conditioning therapy, you will get your donor’s cells.

When are allo transplants used?

Allo transplants are most often used to treat:

• Certain types of leukemia
• Lymphomas
• Myelodysplastic syndromes
• Other bone marrow disorders, such as aplastic anemia

Benefits of allo stem cell transplant

• The donor stem cells could help kill any cancer cells that remain after high-dose treatment. This is called the graft-versus-cancer or graft-versus-tumor effect.
• The donor can be asked to donate more stem cells or even white blood cells if needed (although this isn't true for a cord blood transplant).
• Stem cells from healthy donors are free of cancer cells.

Risks of allo stem cell transplant

As with any type of transplant, there is a risk that the transplant (or graft) might not take. The transplanted donor stem cells could die or be destroyed by your body before settling in your bone marrow.

Other risks:

• Graft-versus-host disease: The immune cells from the donor could see your tissue as strange and attack healthy cells in your body. This is called graft-versus-host-disease (GVHD). While prevention and treatment for GVHD has greatly improved in recent years, GVHD can range from mild to life-threatening.
• Infections from donor cells: There might be certain infections from the donor cells, even though donors are tested before they donate. This is a small risk.
• Old infections becoming active: Some types of infection you had before transplant could resurface after an allo transplant. Your immune system might’ve had the infection under control, but it could resurface now that your immune system is weakened (suppressed) by medicines called immunosuppressive drugs.

These infections can cause serious problems and can even be life-threatening.

For more on these risks, see Stem Cell or Bone Marrow Transplant Side Effects.

Reduced intensity conditioning (RIC) transplant

For some people, age or certain health conditions may make getting myeloablative therapy a higher risk. (Myeloablative therapy is the treatment that wipes out all your bone marrow before a transplant.)

To reduce this risk, doctors can use a RIC transplant.

This is sometimes also called a mini transplant or a non-myeloablative transplant.

How does a RIC transplant work?

People who get RIC transplants typically get lower doses of chemo and/or radiation than a standard myeloablative transplant.

The goal in a RIC transplant is to kill some of the cancer cells (which will also kill some of the bone marrow) and suppress your immune system just enough to allow the donor stem cells to settle in your bone marrow.

Unlike a standard allo transplant, both your cells and the donor’s cells remain in your body. Over the course of months, the donor cells slowly take over the bone marrow and replace your own bone marrow cells.

These new cells can then develop an immune response to the cancer and help kill off your cancer cells. (This is called the graft-versus-cancer effect.)

Advantages and disadvantages of a RIC transplant

An advantage of a RIC transplant is that it uses lower doses of chemo and/or radiation. All your stem cells aren’t killed, and your blood cell counts don’t drop as low while you wait for the new stem cells to start making normal blood cells.

This makes RIC transplants useful for older people and those with other health problems. Rarely, it may be used in people who have already had a transplant.

RIC transplants treat some diseases better than others. They may not work well for people with a lot of cancer in their body or people with fast-growing cancers.

Even though there might be fewer side effects from chemo and radiation compared to a standard allo transplant, the risk of graft-versus-host disease is the same.

Some studies have shown that for certain cancers and other blood conditions, both adults and children can have the same kinds of results with a RIC transplant as they would with a standard transplant.

Syngeneic stem cell transplant

This is a special kind of allo transplant that can only be used if you have an identical sibling (twin or triplet) — someone with the exact same tissue type.

Advantages of syngeneic stem cell transplant

• Graft-versus-host disease isn’t a problem.
• There are no cancer cells in the transplanted stem cells

Disadvantages of syngeneic stem cell transplant

Because your sibling donor’s immune system is so much like your own immune system, there is no graft-versus-cancer effect. This is a disadvantage because the new stem cells can’t help kill any remaining cancer cells.

Your donor’s stem cells are identical to yours, so these donor cells might not see the cancer as a threat and won’t try to kill it. To help keep the cancer from coming back, every effort must be made to destroy all cancer cells before the transplant happens.

Umbilical cord blood transplant

Umbilical cord blood (or cord blood) transplant is a type of allo transplant. It uses blood taken from the placenta and umbilical cord after a baby is born. This small volume of cord blood has a high number of stem cells.

Benefits of cord blood transplant

• There are a large number of donated units in cord blood banks, so finding a donor match might be easier.
• Cord blood units have already been donated, so they don’t need to be collected once a match is found.
• A cord blood transplant is also less likely to be rejected by your body than a transplant from an adult donor.

Downsides of cord blood transplant

• There aren’t as many stem cells in a cord blood unit as there are in a typical transplant from an adult donor. Because of this, cord blood transplants are used more often for children, who have smaller body sizes.
• These transplants can be used for adults as well, although sometimes a person might need to get more than one cord blood unit to make sure there are enough stem cells for the transplant. This is called pooled umbilical cord blood.

Cord blood transplants can also take longer to begin making new blood cells. During this time, a person is at risk of infections and other problems caused by having low blood cell counts.

Omidubicel for cord blood transplants

There is a newer cord blood product known as omidubicel. These cord blood cells are treated in a lab with a special chemical that helps the donated cells get to the bone marrow and start making new blood cells more quickly.

Over the years, cord blood transplants have become less common and half-matched (haploidentical) transplants have increased, with positive results.

Half-matched transplant (haploidentical)

Improvements have been made in the use of family members as donors. For people who don’t have a fully matched or identical family member, a half-match (haploidentical) transplant might be an option.

Half-matches can come from family members such as parents, children, full or half siblings, and even cousins. This can be another option to consider, along with cord blood transplant and matched unrelated donor (MUD) transplant.

Mismatched unrelated donor (MMUD) transplant

A mismatched unrelated donor (MMUD) transplant might be an option if you don’t have a fully matched or half-matched related (haploidentical) donor.

For this type of transplant, an unrelated donor is found through a registry, just like matched unrelated donors (MUD). But in this case, the donor has slight mismatches — more than a half match but less than a full match.

MMUD transplants are more common in recent years because doctors have new, improved ways for graft-versus-host-disease (GVHD) prevention with better outcomes. Research shows that using a medicine called post-transplant cyclophosphamide for GVHD prevention can improve outcomes for MMUD transplants.

Learn more

• Getting a Stem Cell or Bone Marrow Transplant
• Finding a Stem Cell Donor
• Stem Cell Transplant Side Effects