Bone marrow or peripheral blood stem cell transplant for chronic myeloid leukemia

Normal doses of chemotherapy (chemo) can harm normal cells as well as cancer cells. A stem cell transplant offers a way for doctors to use the very high doses of chemo needed to kill all the leukemia cells. Although the drugs destroy the patient's bone marrow, transplanted stem cells given after the chemo can restore the blood-making bone marrow stem cells. This is called a stem cell transplant (SCT).

Stem cells for transplant are most often collected from the bone marrow or from the bloodstream (in a process called apheresis). Sometimes umbilical cord stem cells are used. Bone marrow transplant was more common in the past. Now it has been largely replaced by cells taken from the bloodstream (called peripheral blood stem cell transplant or PBSCT).

These blood-forming stem cells can come from either the patient or from a donor whose tissue type closely matches that of the patient. The donor may be a brother or sister or – less often – a person not related to the patient.

The transplant process

First, blood-forming stem cells are collected from either the patient or a matched donor. The cells are frozen and stored. Patients are then given very high doses of chemo to kill the cancer cells. They may also get total body radiation to kill any remaining cancer cells. After treatment, the stored stem cells are given to the patient into a vein like a blood transfusion. Then the waiting begins as the stem cells settle in the patient's bone marrow and start to grow and produce blood cells.

People who get a donor's stem cells are given drugs to prevent rejection as well as other medicines to prevent infections. Usually within a couple of weeks after the stem cells are put in (infused) they begin making new white blood cells. Then they begin making platelets, and finally, red blood cells.

Patients having SCT have to be kept away from germs (in protective isolation) as much as possible until their white blood cell count is at a safe level. They may be able to leave the hospital when their white blood cell count is near 1,000. Even after they go home, they will be seen in the outpatient clinic almost every day for many weeks.

"Mini-transplants"

Most patients over the age of 55 can't withstand a regular transplant that uses high doses of chemo. But some may be able to have what is called a "mini-transplant" (also called a non-myeloablative transplant or reduced-intensity transplant). In this type of transplant, patients get lower doses of chemo and radiation which do not destroy the all cells in their bone marrow. They then get the donor stem cells. These new cells enter the body and form a new immune system, which sees the leukemia cells as foreign and attacks them (called a "graft-versus-leukemia" effect). This approach is not often used in CML.

Side effects of SCT

Side effects from a stem cell transplant can be divided into early and long-term effects.

Early side effects: Early side effects are about the same as those of any other type of high-dose chemo – low blood cell counts, nausea, vomiting, hair loss, mouth and throat sores. They are caused by damage to the bone marrow and other tissues of the body that grow and divide fast.

One of the most common and serious side effects is the increased risk of infection. Antibiotics are often given for a time, even before there are any signs of infection, to try to keep this from happening.

Long-term side effects: Some side effects can go on for a long time. And sometimes they don't show up until years after the transplant. Long-term side effects could include the following:

• Graft-versus-host disease (see below)
• Radiation damage to the lungs, causing shortness of breath
• Damage to the ovaries causing infertility and loss of menstrual periods
• Damage to the thyroid gland that causes problems with the way the body uses energy
• Cataracts (damage to the lens of the eye)
• Bone damage, which can be so bad that part of the bone and joint must be replaced

Graft-versus-host disease or GVHD is the main problem of a donor stem cell transplant. It happens when the immune system of the patient is taken over by that of the donor. The donor's immune system then begins reacting against the patient's other tissues and organs.

Symptoms of GVHD can include weakness, dry mouth, nausea, severe skin rashes with itching, and severe diarrhea. The liver and lungs may also be damaged. The patient may also become tired and have aching muscles. If bad enough, GVHD can be fatal. Drugs that weaken the immune system are often given to try to keep GVHD under control.

Some things to keep in mind

Before modern targeted therapy drugs like imatinib (Gleevec), SCT was commonly used to treat CML. Before drugs like Gleevec were available, less than half of patients lived more than 5 years after diagnosis. Now, these drugs are the standard treatment, and transplants are being used less often. Still, a SCT from a donor offers the only proven chance to cure this disease, and many doctors will recommend a transplant for younger patients. Results seem to be best when the stem cell donor is a well-matched brother or sister. Results are also better when the transplant is done earlier in the course of the disease. Transplant may also be recommended if the CML is not responding well to the new drugs.

Stem cell transplantation is a complex and risky treatment. It is important that it be done at a hospital where the staff is experienced with the process. Some transplant programs may not have experience in certain transplants, especially those from unrelated donors.

Stem cell transplantation also costs a lot (more than $100,000) and often means a long hospital stay. You should find out what your insurance will cover and what you might have to pay before choosing to have a transplant.

For more information on stem cell transplants, see our document, Stem Cell Transplant (Peripheral Blood, Bone Marrow, and Cord Blood Transplants).