The usual doses of chemotherapy drugs can cause serious side effects to quickly dividing tissues such as the bone marrow. Even though higher doses of these drugs might be better at killing leukemia cells, they are not given because the severe damage to bone marrow cells would cause lethal shortages of blood cells.
For a stem cell transplant (SCT), high doses of chemotherapy are given to kill the leukemia cells. Sometimes the whole body also is given a low dose of radiation. This treatment kills the leukemia cells, but also damages the normal bone marrow cells. Then after these treatments, the patient receives a transplant of blood-forming stem cells to restore the bone marrow.
Blood-forming stem cells used for a transplant are obtained either from the blood (called a peripheral blood stem cell transplant, or PBSCT) or from the bone marrow (called a bone marrow transplant, or BMT). Bone marrow transplant was more common in the past, but it has largely been replaced by PBSCT.
The 2 main types of stem cell transplants are allogeneic and autologous.
For an autologous transplant, the patient’s own stem cells are collected from the blood or bone marrow and then given back after treatment. The problem with that is that leukemia cells may be collected with the stem cells.
In an allogeneic transplant, the stem cells come from someone else (a donor). To lower the chance of complications, the donor needs to “match” the patient in terms of tissue type. Often, a close relative, such as a brother or sister is a good match. Less often, a matched unrelated donor may be found.
Because collecting the patient’s stem cells can also collect leukemia cells, allogeneic transplants are the main type of transplant used to treat patients with chronic myeloid leukemia (CML). Allogeneic stem cell transplant is the only known cure for CML. Still, this type of transplant can cause severe or even life-threatening complications and side effects, and it is often not be a good option in people who are older or have other health problems.
Before modern targeted therapy drugs like imatinib (Gleevec), SCT was commonly used to treat CML. The drugs that were available at that time did not work very well, and fewer than half of patients survived more than 5 years after diagnosis. Now, targeted drugs like imatinib are the standard treatment, and transplants are being used less often. Still, because allogeneic SCT offers the only proven chance to cure CML, doctors may still recommend a transplant for younger patients, particularly children. It is more likely to be considered for those with an available matched donor, like a well-matched brother or sister. Transplant may also be recommended if the CML is not responding well to the targeted drugs.
For more information on stem cell transplants, see Stem Cell Transplant (Peripheral Blood, Bone Marrow, and Cord Blood Transplants).
Last Revised: 02/22/2016