Blood & Marrow Transplantation Program
Treatment
Sources of Stem Cells for Transplant
The source of stem cells for transplantation depends on your disease, age, medical condition and the availability of a suitable stem cell donor. There are several sources of stem cells for transplant.
Autologous: Stem cells are taken from the patient, usually from the circulating (peripheral) blood. These cells are then frozen and stored for future use. These cells are commonly used within a few days after they are obtained since patients require prompt therapy.
Syngeneic: Bone marrow or peripheral blood stem cells are obtained from an identical twin and given back to the patient. This is the rarest type of transplant.
Allogeneic: Stem cells are taken from a donor and given to the patient. These stem cells are usually obtained from the donor's blood after treatment with white cell growth factors, although they can also be obtained from the donor's marrow. There is a 25% chance that a brother or sister is a tissue (HLA)-match and can serve as the donor, but occasionally other close relatives, such as a parent or a child, can serve as donors. If there are no tissue-matched family donors, stem cells can be obtained from an HLA-matched unrelated volunteer donor identified from a large registry called the National Marrow Donor Program. This alternative greatly expands the number of people who are candidates for transplants, and now more than half of our allogeneic transplants are from an unrelated volunteer donor. Moffitt Cancer Center participates in this registry program both as a transplant center and as a donor collection facility.
Umbilical Cord: Stem cells can also be obtained from the umbilical cord of the placenta following a normal delivery of a child and then frozen and stored for later use. This type of transplant is an allogeneic transplant. Umbilical cord blood banks can store and maintain a list of potential units. This type of transplant is more commonly used in children, although umbilical cord blood transplants can be performed in adults.
Donor Selection
If an allogeneic transplant is recommended, only people who are closely "HLA-matched" with the patients are used as donors. HLA refers to human leukocyte antigen and represents the tissue types that are the target of transplant reactions. Patient and donor white blood cells are checked using specialized tests to “type” the DNA for HLA-A, B, C, DR and DQ genes.
Red cell types do not need to be the same for the donor and recipient, nor does the gender of the donor and recipient need to match. Donors are screened for their ability to tolerate a stem cell harvest as well as for other potential problems that would make them unable to donate (for example, active infections that could be transmitted to the donor).
Since each HLA gene has two components, for some patients the best possible match will be a 10/10 match, while for others it will be a 9/10 or an 8/10 match. Transplants from a 9/10 or an 8/10 donor have a greater risk of rejection and graft-versus-host-disease (see below about GVHD).
Types of Transplants Available at Moffitt
The Blood & Marrow Transplant Program offers different types of transplants. These include allogeneic transplants from matched or mismatched related or unrelated donors as well as autologous transplants. Transplants are performed in the inpatient or outpatient setting. Decisions are individualized and will depend on the patient's disease, donor availability and other medical and social factors. Allogeneic transplants have a higher risk of lengthy toxic side effects and a longer time to full recovery. Allogeneic transplants, however, allow a beneficial reaction to occur, called the graft-versus-tumor effect, in which the new donor immune system attacks the cancer.
Outpatient transplants are performed at the Moffitt Clinic. Patients are evaluated daily while they receive chemotherapy, irradiation, the stem cell transplant and supportive care. Patients are required to stay in the immediate vicinity of the hospital. They are admitted to the hospital when indicated by their medical condition.
Reduced-Intensity Transplants, also known as “nonmyeloablative transplants” or “mini transplants,” refer to conditioning regimens designed to reduce treatment-related side effects of allogeneic transplants by decreasing the total doses of chemotherapy or radiation therapy given in preparation for the transplants. The donor's marrow or blood stem cells are given to the patient after the conditioning. The donor immune cells grow slowly over several months. This slow process can decrease the early side effects of stem cell transplantation and allow the recipient to eventually convert to the new donor immune system. A reduced-intensity transplant still allows the graft-versus-tumor effect, in which the new donor immune system attacks the leukemia or other cancer.
Donor lymphocyte infusion (DLI) is a therapy to treat recurrence of certain malignancies following allogeneic transplant. It may involve further administration of chemotherapy, and always involves the infusion of donor lymphocytes collected from the blood. Durable remissions can occur following DLI.