Non-myeloablative stem cell transplants, or “mini-transplants,” are a relatively new type of allogeneic peripheral stem cell transplant which do not require ablating (wiping out) the marrow to the degree of traditional stem cell transplants. They are also called reduced-intensity allogeneic transplants.
How They Work
In traditional stem cell transplants, patients are given extremely high doses of chemotherapy, with or without radiation, to wipe out, or “ablate,” the marrow. Then they are given an infusion of donor stem cells to revive blood cell production and immunity.
The intensive doses of chemotherapy and radiation given in traditional stem cell transplants may not be the only thing responsible for their success in cancer remission. Non-myeloablative stem cell transplants use much smaller doses of chemotherapy to achieve a positive outcome.
Graft vs. Malignancy
The principle behind the potential success of this type of transplant is called the “graft- versus-malignancy” (GVM), “graft-versus-tumor,” or “graft-versus-leukemia” effect. Once the donor stem cells are infused into the recipient, the “new” immune system recognizes that any remaining cancer cells are abnormal and destroys them.
Difference From Myeloablative Stem Cell Transplants
Non-myeloablative transplants differ primarily in what happens prior to the transplant. Compared to myeloablative transplants, mini-transplants use much lower and less toxic doses of chemotherapy and radiation, followed by the infusion of donor stem cells. This process takes advantage of the graft vs malignancy effect while being less toxic to the recipient.
As with traditional stem cell transplants, mini-transplants also carry the risk of graft vs. host disease, in which the transplanted cells see your cells as foreign and attack.
This type of transplant may be a good option for patients who are older in age or who have other medical conditions that would make them unable to tolerate the toxic chemotherapy effects of regular transplants.
Non-myeloablative stem cell transplant may also have a role in treating patients who are in remission with high-risk cancer, such as acute myelogenous leukemia, or who have had a relapse after a previous stem cell transplant.
Researchers are also looking at the success of non-myeloablative stem cell transplant in patients with solid tumor cancers, such as breast and kidney, as well as other medical conditions such as multiple sclerosis.
Since it takes a while for the donated cells to mature, these transplants aren’t usually used when cancer is in its most advanced stages.
Non-myeloablative transplants have been used to treat different types of blood cancers, including Hodgkin and non-Hodgkin lymphoma, myeloma, and leukemia. Response rates have varied in studies.
This a very new procedure, with the first one being done less than 20 years ago, so there is limited long-term research available for benefits and risks associated with this type of transplant. However, initial promising results give hope to patients who would otherwise not be able to receive a stem cell transplant, especially those between the ages of 50 and 75.