The MDS Beacon™

This article is part of a series about stem cell transplantation in MDS, which will be published over the next couple of weeks. The series will explain the different types of stem cell transplants, describe the procedure for both patient and donor, address benefits and risks, and talk about prognosis and life after a transplant.

Introduction

Myelodysplastic syndromes (MDS) are a group of diseases that affect the production of stem cells in the bone marrow. Patients with MDS frequently overproduce stem cells. However, many of these cells are abnormally shaped and die prematurely.

Therefore, the stem cells are not able to develop into blood cells properly. Because their bone marrow stem cells do not mature correctly, MDS patients often experience anemia (low red blood cell count), neutropenia (low white blood cell count), and thrombocytopenia (low platelet count). (For more information, please see a related Beacon article about MDS symptoms.)

To return blood counts to normal, the patient must have healthy stem cells that are able to develop into blood cells. This can be achieved through stem cell transplantation, in which healthy stem cells are transplanted from a donor to the patient.

Stem cell transplants are currently the only known cure for patients with MDS.  However, they may not be safe for all MDS patients due to complications. In general, stem cell transplants are recommended for otherwise healthy MDS patients under the age of 55 years.

Sources of Stem Cell Transplants

Stem cells for transplantation can come from peripheral blood, bone marrow, or umbilical cord blood.

Peripheral Blood Cells
Peripheral blood stem cells are the most commonly used source of stem cells. Before the donation, donors are often given medication to mobilize the stem cells from the bone marrow into the blood. The donation procedure is similar to a blood draw. Blood is removed from a vein in the arm and flows into a machine that separates the stem cells from other components of the blood. Only the stem cells are needed, so the rest of the blood is returned to the donor.

Bone Marrow
Bone marrow is another source of blood-forming stem cells that can be used for transplantation. The procedure of bone marrow donation poses a higher risk to donors than peripheral blood donation – it is a surgical procedure and the donor is usually put under general anesthesia. Bone marrow is withdrawn from the back of the pelvic bone by a needle. It is an outpatient procedure that typically requires no more than a day in the hospital

Umbilical Cord Blood
Umbilical cord transplants are performed using stem cells harvested from a frozen umbilical cord. Umbilical cords used for this purpose are harvested at birth and preserved through freezing. Public cord blood banks accept umbilical cords as donations that anyone can use. Private cord blood banks preserve umbilical cords for the sole use of the people who store them.

Types of Stem Cell Transplants

The donor for the stem cells can be the patient himself/herself, or the stem cells can be provided by a donor.

Syngeneic
A syngeneic stem cell transplant is the transplantion of stem cells between identical twins. This type of treatment is ideal because the donor and recipient have the same DNA.  The recipient’s immune system will not recognize the transplanted stem cells as invaders and attack them – an effect called graft vs. host disease. This type of transplantation is very rare and not an option for most patients.

Allogeneic
In allogeneic stem cell transplants, which are the most common type of transplant for MDS patients, the donor and the recipient are two separate people and are not identical twins. Prior to the stem cell transplant, the patient undergoes chemotherapy or radiation to destroy their own abnormal stem cells.

For a successful allogeneic transplant, the stem cell donor must have a human leukocyte antigen (HLA) tissue type that closely matches that of the MDS patient receiving the bone marrow. HLA is found on the surface of cells and marks them as “self” cells, indicating that they belong to that person.

Patients who receive stem cell donations from a donor without closely matched HLA risk the transplanted cells not recognizing the recipient’s body as “self” and attacking the recipient.

Full siblings have the greatest chance of having a highly matching HLA (25 percent). Parents, other relatives, and unrelated people can also be donors. Doctors can search the “Be The Match Registry” for matching volunteer donors and cord blood. For information on how to become a bone marrow donor, please see the National Marrow Donor Program website.

Autologous
An autologous transplant means a patient’s own bone marrow stem cells are collected and then given back to the patient after chemotherapy or radiation treatment.

Autologous transplants have a lower risk of side effects and rejection than allogeneic bone marrow transplants. Despite these benefits, autologous bone marrow transplants are not widely used in MDS treatment because the patients’ own bone marrow cells are unhealthy. Instead, MDS patients need healthy bone marrow cells from a donor.

For more information on the bone marrow transplantation process, its benefits and risks, and the experiences of MDS patients who have received a bone marrow transplant, please see the subsequent articles in the series, which will be published over the next few weeks.