Allogeneic stem cell transplants refer to stem cells that are taken from one person and given to another. With these transplants, the donor's cells must match the recipient's tissue type (much like a blood transfusion needing to match the blood type of the person receiving it). In many cases, the stem cell donor is related to the recipient, typically a brother or sister. However, stem cells from unrelated donors can be used if the tissue types matches. It may also be possible to use cells from banked cord blood.

Currently, high-dose therapy in conjunction with allogeneic stem cell transplant is rarely performed for treatment of myeloma in the United States outside of clinical trials. However, slightly more of these procedures are performed in Europe. The current trend is the use of mini (non-myeloablative) allogeneic transplants.

Studies have shown that allogeneic stem cell transplants lead to prolonged disease-free survival in a relatively small percentage of patients. In addition, the relapse rate is lower than that seen with autologous transplants (approximately 30%-50%). However, allogeneic transplants are associated with a greater risk of complications than autologous transplants, including infections and graft-versus-host disease (GVHD).

During GVHD, the donor immune cells may attack specific organs of the host such as the skin, liver, or gastrointestinal tract. GVHD is typically referred to as acute when it occurs within the first 3 months after transplantation and chronic when it occurs after 3 months. Although GVHD can be prevented or controlled in some cases with immunosuppressive drugs, severe organ failure can result. This is due to the fact that cells from the donor and the patient, although matched for tissue type, are still considered foreign to each other. Because GVHD can have serious consequences, allografts are associated with significant mortality (20% to 50%, depending on the duration of therapy prior to transplantation). Because the risks associated with allogeneic transplants outweigh the potential benefits of the procedure, these types of transplants are now rarely performed in the US outside of clinical trials.

Because the conditions required for allogeneic transplants are rigorous and the potential for adverse events is higher, these types of transplants are typically not performed in patients aged 55 or older or in patients in poor overall health. They may be considered in the context of a clinical trial for younger patients with progressive disease following an autologous transplant, for patients with responsive or stable disease after initial chemotherapy, or as salvage therapy.

Since allografts come from an individual other than the patient, they have the benefit of not containing tumor cells. A potential benefit of allogeneic transplants is their ability to help the patient fight against the myeloma tumor. Just as immune cells in the allograft attack the patient's tissue, they also help attack the tumor, a phenomenon referred to as a graft-versus-myeloma effect. This effect may account in part for the lower relapse rates seen following allogeneic transplants compared to autologous transplants. However, one must still consider the significantly higher mortality seen with allogeneic transplants.

Researchers are working to harness the antitumor effect of allogeneic transplants while making them safer. For example, there is much ongoing research in the use of mini-allogeneic transplants in myeloma.

Find out more about mini-allogeneic transplants

Ongoing Allogeneic Stem Cell Transplant Trials in Myeloma as of August 2005 UARK 99-036, Filgrastim-Mobilized Peripheral Blood Stem Cells for Primary Allogeneic Transplantation with Unrelated Donors •  View trial information Non-treatment studies UARK 2003-15 Protocol for a Research Sample Repository for Allogeneic Unrelated Hematopoietic Stem Cell Transplantation •  View trial information UARK 2003-16 Research Database for Unrelated Donor Transplant •  View trial information