Despite the good track record of Gleevec® and similar drugs, some chronic myeloid leukemia (CML) patients have poor responses to the therapy. If you fall into this category, your doctor may suggest stem cell transplantation.
Allogeneic stem cell transplantation is the best-documented curative treatment for CML at this time. However, because of the high, sometimes life-threatening, risks associated with stem cell transplantation, doctors rarely use it as a initial treatment.
The decision to undergo stem cell transplantation has become more complicated with the introduction of tyrosine kinase inhibitors (TKIs) to manage CML. It's important to weigh the risks and benefits of stem cell transplantation with your doctor as you consider your treatment options.
This treatment is most successful in younger patients.
Although it's not the only type of stem cell transplantation, allogeneic stem cell transplantation is the most common and used almost exclusively to treat CML.
Allogeneic Stem Cell Transplantation
Allogeneic stem cell transplantation involves transferring stem cells from a healthy person (the donor) to the patient. The procedure follows high-intensity chemotherapy, potent drugs that must be toxic enough to kill leukemic cells. Unfortunately, the drugs also take aim at normal stem cells in the bone marrow.
The main reasons for doing an allogeneic stem cell transplant are:
- To start a new supply of red cells, white cells and platelets with help from the transplanted donor stem cells
- To give strong doses of chemotherapy to kill CML cells
The decision to do a stem cell transplant depends on:
- The availability of a matched donor
- Your response to oral drug therapy
- Your understanding of the transplant's benefits and risks
Reduced-Intensity Allogeneic Stem Cell Transplantation
If you can't tolerate allogeneic with high-intensity chemotherapy, you may be eligible for reduced-intensity stem cell transplantation (sometimes called nonmyeloablative transplant). This type of transplant is a modified version of allogeneic transplantation that's been effective for many CML patients.
To prepare for the transplant, you undergo less-intense conditioning treatment compared with a standard allogeneic transplant. The chemotherapy destroys most cancer cells with a standard transplant. Reduced-intensity conditioning doesn't destroy many cancer cells but instead relies on the donor's immune cells to fight the disease. This attack is called the graft-versus-tumor (GVT) effect.
Graft Versus Host Disease
A serious risk of allogeneic and reduced-intensity allogeneic stem cell transplantation is graft versus host disease (GVHD), which develops if the donor's immune cells attack your normal tissue. GVHD's effects can range from minor to life threatening.
Donor Lymphocyte Infusion
Of the CML patients who undergo allogeneic transplantation, about 70 percent or more are cured. But, for patients who relapse, donor lymphocyte infusion therapy may induce (bring about) an immune reaction against their cancer cells. During this procedure, doctors transfer lymphocytes (a type of white cell) from the original stem cell donor's blood to the patient. The goal is to destroy any remaining cancer cells to achieve the GVT effect.