Chronic Myeloid Leukemia (CML): Stem Cell Transplant

What is a stem cell transplant?

Stem cells are immature cells. These are the starter cells for all types of body tissues. A stem cell transplant uses stem cells to replace bone marrow that contains cancer. These stem cells will grow and become new and healthy bone marrow that makes healthy blood cells. The bone marrow with cancer is first destroyed with high-dose chemotherapy. Or, this may be done with radiation to the whole body. Healthy stem cells are then put in your body. 

When might a stem cell transplant be used for CML?

This treatment is done less often for chronic myeloid leukemia (CML) than targeted therapy, such as imatinib. But it still may be a valuable choice for some people. A healthcare provider may wait and see how you respond to targeted therapy before doing a stem cell transplant.

Although a stem cell transplant may cure CML, the benefit has to be weighed against the risks. There is a possibility that you can die from the complications of the transplant. Your healthcare provider may recommend a stem cell transplant if you’re younger and fairly healthy, and any of these apply to you: 

• Your CML is in the chronic phase, and targeted therapy is not working. Most people with CML are treated with targeted therapy first. But a stem cell transplant may be offered if targeted therapy doesn’t work or stops working, especially in young people.

• Your CML is in the accelerated phase. Targeted therapy doesn’t work as well during the accelerated phase. In these cases, a stem cell transplant may be advised.

• Your CML is in the blast phase. Targeted therapy alone is unlikely to work in the blast phase. In these cases, a stem cell transplant may be advised.

Types of stem cell transplants

There are two kinds of stem cell transplants:

• Allogeneic transplant. This means the stem cells come from another person. This may be a brother or sister.

• Autologous transplant. This means the stem cells are collected from your own body and preserved. This is done before you get chemotherapy.

For CML, stem cells from a matched donor are preferred over using your own stem cells. In many cases this may be a family member. But stem cells may also come from a matched, unrelated donor if no family member has the same tissue type as you.

How stem cells are collected 

Stem cells may be obtained in one of two ways:

• From the blood. This is the most common source of stem cells for a transplant. You or your donor may get an injection of a growth factor medicine for several days. This medicine helps stimulate stem-cell production. The process for collecting stem cells from the blood is called apheresis. It’s a lot like giving blood, but it takes longer. A thin, flexible tube called a catheter is used to get blood from your vein or from a donor. The blood goes to a device to remove the stem cells. The stem cells are then frozen until needed later. Then the extra blood is returned to you or the donor. This process may need to be done more than once to collect the right amount of cells.

• From the bone marrow. Stem cells may also be taken from the bone marrow of you or the donor. This process is done while you or your donor is asleep with general anesthesia. A healthcare provider makes several punctures in the pelvic or hip bone to remove marrow. These stem cells are filtered and frozen until they are needed.

Having the transplant

• You may be admitted to the hospital the day before your transplant. 

• You will be given chemotherapy or radiation therapy to treat the leukemia.

• After the chemotherapy or radiation therapy is finished, you will receive the stored stem cells through a thin needle that is put into your arm and attached to a tube. This is similar to a blood transfusion.

• You will then have to wait for your stem cells to start multiplying. You may have to stay in isolation away from people to avoid getting an infection. Once the part of your white blood cell count (absolute neutrophil count) reaches a safe level, you can come out of isolation and then eventually go home. This may happen within several weeks, or it may take longer.

• You will need to have your blood drawn often to check your blood cell count for the next several weeks. This can be done on an outpatient basis.                                                                              

What is a mini-transplant?

A mini-transplant is sometimes used for a person with CML who can’t tolerate a standard stem cell transplant. It’s also called a nonmyeloablative transplant. Or it may be called a reduced intensity allogeneic transplant

The treatment is done with a lower dose of chemotherapy or radiation. This doesn't fully destroy the cells in the bone marrow. But it’s enough to keep the immune system in check. Then you receive donor stem cells. These stem cells later develop an immune reaction to the leukemia cells and kill them. Because this treatment uses lower doses of chemotherapy or radiation, it often has less severe side effects. Older adults or people with other health problems can often tolerate this treatment better.

Many doctors still consider mini transplants to be experimental for CML and believe that they are best done as part of a clinical trial. 

Possible short-term side effects

Most of the short-term side effects of a stem cell transplant are from the high doses of chemotherapy or radiation. These should go away as you recover from the transplant. Common side effects can include:

• Infections

• Low blood cell counts

• Bleeding

• Low blood pressure

• Shortness of breath

• Chest pain or tightness

• Coughing

• Fever or chills

• Hair loss

• Nausea

• Vomiting

• Mouth sores

• Loss of appetite

• Diarrhea

• Tiredness (fatigue)

• Weakness

Possible long-term side effects

Some side effects of a stem cell transplant may be long-lasting or appear years later, such as:

• Bone pain

• Growth of another cancer

• Shortness of breath, often caused by radiation damage to the lungs

• Damage to the liver, kidneys, or other organs

• Lack of menstrual periods, which may mean damage to the ovary causing infertility

• Vision problems caused by damage to the lens of the eye

• Weight gain, which may be a sign of thyroid gland damage

Another possible long-term side effect is graft-versus-host disease. This can only occur with an allogeneic transplant. The immune system cells in the donor's stem cells attack your body. The cells can attack your skin, liver, gastrointestinal tract, mouth, or other organs. This can cause symptoms such as:

• Skin rashes with itching

• Yellowing of the skin (jaundice)

• Severe diarrhea

• Fatigue

• Muscle aches 

Making a decision

It's important to discuss the procedure with your healthcare provider to make sure you understand the possible risks and benefits. 

Stem cell transplant is a complex procedure. It’s only done by healthcare providers with special training. If you decide to have one, go to a hospital that specializes in stem cell transplants, such as a major cancer center. The procedure is also expensive. Make sure to check with your insurance provider to see how much of it will be covered.