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 receives 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 receives new, functioning blood-forming stem cells. There are 2 main types of SCT: 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 contains abnormal stem cells.

For an allogeneic stem cell transplant, the patient receives 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, the donor is matched to the patient, but is not related.

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 restrict this treatment to people younger than a certain age.

A special type of allogeneic transplant, called 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. For this kind of transplant, the doses of chemotherapy 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 are just enough to allow the donor cells to take hold and grow in the bone marrow. The lower doses of chemotherapy and/or radiation cause fewer side effects, which makes this type of transplant easier for older patients to tolerate. Still, some serious side effects remain.

Transplant side effects

The early side effects from a SCT are similar to the side effects expected from chemotherapy and radiation, only more severe. One of the most serious side effects is low blood counts, which can lead to risks of serious infections and bleeding.

The most serious side effect from allogeneic transplants is called graft-versus-host disease (or GVHD). This occurs when the new immune cells (from the donor) see the patient’s tissues as foreign and so attack them. This can affect any part of the body and can be life threatening.

Allogeneic SCT is currently the only treatment that can cure some patients with CMML, but not all patients who get a transplant are cured. And many patients may die from complications of this treatment.

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