Stem Cell Transplant for Chronic Myelomonocytic Leukemia

Stem cell transplant (SCT) is the only treatment that can cure chronic myelomonocytic leukemia (CMML). In this treatment, the patient gets high-dose chemotherapy often along with radiation to the entire body to kill the cells in the bone marrow (including the abnormal bone marrow cells). Then the patient is given new, healthy blood-forming stem cells. The 2 main types of SCT are: allogeneic and autologous.

In an autologous stem cell transplant, after the bone marrow is destroyed, the patient gets back their own stem cells. This type of transplant is not a standard treatment for patients with CMML because their bone marrow has abnormal stem cells.

For an allogeneic stem cell transplant, the patient gets blood-forming stem cells from another person -- the donor. The best results are when the donor’s cells are closely matched to the patient’s cell type and the donor is closely related to the patient, such as a brother or sister. Less often, an unrelated donor is matched to the patient.

Allogeneic stem cell transplant can have serious, even fatal, side effects and so is rarely used in elderly patients. Because of these side effects, some doctors only use this treatment for people younger than a certain age.

A special type of allogeneic transplant, a non-myeloablative allogeneic stem cell transplant, may be an option for older patients. This type of transplant is sometimes called a mini-transplant or a mini-allo. In this type, the doses of chemo and/or radiation that are given are lower than those used for a standard allogeneic transplant. These doses are not high enough to kill all the bone marrow cells, but they kill just enough to allow the donor cells to take hold and grow in the bone marrow. The lower doses of chemo and/or radiation cause fewer side effects, which makes this type of transplant easier for older patients to tolerate. Still, it has some serious side effects.

For now, allogeneic SCT is the only treatment that can cure some patients with CMML, but not all patients who get a transplant are cured. And patients can die from complications of this treatment. Also, many people with CMML are not able to get this treatment.