Stem cell transplant for chronic myelomonocytic leukemia

Stem cell transplant (SCT) in the only treatment that can cure CMML. In this treatment, the patient receives high-dose chemotherapy and/or total body irradiation 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.

Autologous transplant

In an autologous stem cell transplant, after the bone marrow is destroyed, the patient is given 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.

Allogeneic transplant

For an allogeneic stem cell transplant, the patient receives blood-forming stem cells from a donor. The donor’s cells must be matched to the patient’s cell type. The best results are seen when the donor is related to the patient, such as a brother or sister. Less often, the donor is matched to the patient, but is not related. Donor stem cells can be taken from multiple bone marrow samples, but more often are taken from the peripheral (circulating) blood by a method known as apheresis. Allogeneic SCT can have serious, even fatal, side effects. It is used most often in younger patients without serious health problems. It is rarely used in elderly patients.

Non-myeloablative transplant: Many elderly patients can’t tolerate the high doses of chemotherapy needed for a standard allogeneic transplant. Some older patients may be able to have a non-myeloablative transplant (also known as a mini-transplant or reduced-intensity transplant). This is a type of allogeneic SCT that uses lower doses of chemotherapy and radiation that do not completely destroy the cells in the bone marrow. After the chemotherapy/radiation, the patient receives the donor stem cells. These cells enter the body and establish a new immune system. The new immune cells see the leukemia cells as foreign and attack them. This is called a graft-versus-leukemia effect.

The lower doses of chemotherapy and radiation involved are less toxic than what is used in a standard allogeneic transplant. This makes non-myeloablative transplant an option for older patients. This type of transplant has fewer side effects, but some serious side effects remain, particularly graft-versus-host disease.

Side effects

Many of the side effects from a SCT are from the high doses of chemotherapy and radiation used. Some early side effects can include:

• Hair loss
• Mouth sores
• Loss of appetite
• Nausea and vomiting
• Low blood counts

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 is more common if the donor is unrelated or if the cells aren’t completely matched. GVHD can occur early in the transplant process. This is called acute GVHD. It can also start later but then last a long time; this is called chronic GVHD.

GVHD can affect the skin, where it can cause a rash, blistering, or open sores. When GVHD affects the intestines, it can cause massive diarrhea. It can also cause problems with the liver and lungs. Drugs to suppress the immune system are given as part of the transplant in order to prevent GVHD. If GVHD develops despite these drugs, additional treatments to suppress the immune system may be needed.

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.

Other side effects may occur over time:

• Damage to the lungs from radiation (this is rare)
• Damage to the ovaries causes infertility and abrupt menopause, usually with symptoms such as hot flashes and loss of menstrual periods.
• Damage to the thyroid gland may produce problems with metabolism.
• Cataracts, clouding of the lens of the eye that can decrease vision, may occur.
• Bone damage (called avascular necrosis or aseptic necrosis) occurs rarely. The bone of the hip joint is affected most often. If it becomes severe, the joint may need to be replaced

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