Stem Cell Transplants
Types of Stem Cell Transplants
Stem cell transplants are classified differently depending on the type of donor (individual providing stem cells):
- Autologous: from the patient
- Allogeneic: from another individual who is genetically similar or matched to the patient.
The donor’s cells must match the patient’s, similar to the matching process used for kidney or other organ transplantation. In many cases, the stem cell donor is related to the recipient, typically a brother or sister. Stem cells from unrelated donors can also be used if there is a match. It may also be possible to use cells from banked cord blood.
Way in which stem cells are obtained or collected:
- Peripheral blood: from the bloodstream
- Bone marrow
The vast majority of stem cell transplants performed in multiple myeloma patients are autologous peripheral blood stem cell (PBSC) transplants. Bone marrow transplants are rarely performed today in myeloma. Historically, these were the first type of stem cell transplants performed, however peripheral blood stem cell transplants put less strain on the body and stem cells are easier to collect. Occasionally, bone marrow transplants may be used if of the number of stem cells that can be obtained from the peripheral blood are insufficient.
Autologous stem cell transplants have several advantages over other types of transplants:
- The patient serves as his or her own source of stem cells. There is no need to find a donor and there is no risk of incompatibility (i.e., a mismatch).
- In many instances, much of the procedure can be done on an outpatient basis.
- They are relatively safe procedures, with low rates of complications and infections compared with allogeneic transplants. Deaths due to the transplant itself are approximately 2% to 3% in patients with newly diagnosed myeloma.
In theory, one disadvantage of autologous stem cell transplants is that the transplant could be potentially contaminated with tumor cells when a patient’s stem cells are used. However, recent studies indicate that this is not a significant problem and is not a major cause of myeloma relapse.
High-dose chemotherapy followed by an allogeneic transplant has the potential to possibly provide better long-term control of myeloma (with longer time without disease progression) than autologous transplants. However, this is a risky procedure with a high death rate due to the procedure itself (20-50%). As a result, this type of transplant is rarely performed.
A safer type of allogeneic transplant is much more common. This type of transplant is called a mini-allogeneic transplant (also called a reduced intensity or non-myeloablative allogeneic transplant). A “mini-transplant” uses lower doses of chemotherapy prior to transplant and as a result the rate of death due to the procedure is very low, similar to that of an autologous transplant.