"Mini" Transplants make Major Impact
Non-Myeloablative Bone Marrow Transplantation for HD

Non-myeloablative allogeneic bone marrow transplants, also known as  "mini-BMTs," offer the cancer treatment benefit of a standard donor bone marrow transplant at much lower levels of toxicity. For this reason, mini-BMT's are becoming a popular option for Hodgkin's Disease patients that aren't able to achieve long term remission from an autologous transplant. Like in an auto transplant where the patient receives an infusion of his/her own stem cells after several days of chemotherapy and radiation, Non-myeloablative transplant patients receive an infusion of donor cells from either a sibling or unrelated donor from a registry. 

Unlike patients receiving a re-infusion of their own cells, allogeneic (donor transplant) patients run the risk of complications of Graft-versus-Host disease (or GVHD). GVHD is a condition that occurs when the donor's immune system cells attack the patient's organs and tissues. When it is mild, GVHD can cause a skin rash or intestinal discomfort. More severe cases of GVHD can cause blistering, peeling skin, and serious liver, stomach and intestinal problems that may be life-threatening. Although the risk of GVHD is high for most patients, there is growing evidence that this fight between the donor cells and the host may be the key to attaining a long term remission. 

With new medical journals publishing an increased success for those patients transplanted allogeneicly, it is becoming clear the donor's white blood cells play a critical role in destroying cancer cells that remain after transplant and high dose therapy. This phenomenon is called the graft-versus-lymphoma or graft-versus-tumor effect. The T-cells contained in the donor’s marrow are potent killers of cancer cells. New thinking brings many researchers to believe that patients who fail a transplant of their own cells will never be able to achieve remission from chemotherapy or radiation alone.

The evidence for this anti-tumor effect includes: 1) Patients receiving allogeneic BMTs relapse less often than those who receive their own bone marrow after receiving the same preparative regimen in other blood related cancers; 2) Patients who develop graft-versus-host disease, or GVHD, relapse less frequently than those patients who do not develop the disease; 3) White cell infusions from the donor, also known as donor-lymphocyte-infusions, may induce remissions of the cancer after a relapse from an allogeneic BMT. Mini-BMT patients may be able to capitalize on the graft-versus-tumor anti-cancer effect if the cancer were to return after initial engraftment;

Several variations of mini-transplants are being pioneered all throughout the United States and Europe. One variation from Seattle uses low dosages of chemotherapy (fludarabine) and a dosage of total body irradiation that is so mild, the procedure can often be performed in the outpatient clinic. Researchers in Houston have developed a different type of reduced intensity transplant that uses moderate dosages of combination chemotherapy (fludarabine with or melphalan) to destroy cancer cells and to suppress the patient's immune system. The goal of this pre-transplant preparative regimen is to prevent donor stem cells from being rejected by the patient, and to kill some of the cancer cells. A third form of reduced intensity transplant, developed by researchers in Israel, uses less toxic dosages of chemotherapy than a  standard stem cell transplant, but higher than dosages given to patients on the Houston style mini- transplant. 

Transplant researchers still have few steps to climb to reach the full potential of mini-transplantation. Managing the Graft-versus-host disease following the donor transplant remains problem that still needs to be resolved since the same drugs used to prevent GVHD also interfere with the ability of the donor's white blood cells to destroy cancer cells that remain in the patient's body after transplant. Mini-transplants have undoubtedly unlocked the key to the bodies natural tumor-killing response and the potential for decreased therapy and higher survival rates for patients at one time with little chance of remission.