Stem Cell Transplant for Chronic Myelomonocytic Leukemia (CMML)

The main types of stem cell transplant (SCT) are autologous and allogeneic.

Autologous stem cell transplants

In an autologous stem cell transplant, a person 'donates' some of their own blood stem cells (from either their blood or bone marrow), which are frozen until they are needed. After the bone marrow is destroyed with chemo and/or radiation, the person gets their own stem cells back. Autologous transplants aren't routinely used to treat CMML, because the person's own blood stem cells are likely to contain leukemia cells as well, which they would get back after the transplant.

Allogeneic stem cell transplants

For an allogeneic stem cell transplant, the person with CMML gets blood-forming stem cells from another person (a 'donor'). This is the type of SCT used for CMML, if it can be done. The results are best when the donor’s cell type is 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, a matched, unrelated donor may be the source of the stem cells.

Allogeneic SCTs can have serious, even life-threatening, side effects, including prolonged low blood cell counts that can make a person very vulnerable to infections, bleeding, and other problems. Because of this, an allogeneic SCT isn't likely to be a good option in people who are older and/or have other major health problems.

A less intense transplant option

A type of transplant known as a non-myeloablative allogeneic stem cell transplant may be an option for some people, especially if they might not be able to tolerate the high doses or chemo and/or radiation. This is sometimes called a mini-transplant or a mini-allo.

For this treatment, the doses of chemo and/or radiation are lower than those used for a standard allogeneic transplant. These doses aren't high enough to kill all the bone marrow cells, but they kill enough to allow the donor cells to take hold and grow in the bone marrow. These donor cells can then help wipe out any remaining leukemia cells. The lower doses of chemo and/or radiation cause fewer side effects, which makes this type of transplant easier for older patients to tolerate. But it can still have some serious side effects.

While an allogeneic SCT offers the best chance to cure some people with CMML, many people with CMML aren't able to get this treatment.