Non-Myeloablative Allogeneic Bone Marrow Transplantation or 'Mini-BMT' The ultimate goal of a non-myeloablative allogeneic bone marrow transplantation ('mini-BMT') is to offer the cancer treatment benefit of a standard allogeneic bone marrow transplant (BMT) with less toxicity. In a standard BMT procedure, very high doses chemotherapy with or without radiation therapy are given to kill as many cancer cells as possible. This treatment also destroys the patient’s bone marrow and immune system. The patient is then 'rescued' by receiving healthy bone marrow from a brother or sister. Because the patient’s immune system has been destroyed, the donor’s bone marrow is not rejected and grows to replace the patient’s bone marrow. In a standard BMT, there are two ways cancer cells are killed: The high doses of therapy before the transplant and donor T cells. T cells, contained in the donor’s marrow, are potent killers of cancer cells. This anti-tumor effect is called the graft-versus-tumor or the graft-versus-leukemia effect. Evidence for this anti-tumor effect include: 1) patients who received allogeneic BMTs relapse less often than those who receive their own bone marrow after receiving the same preparative regimen; 2) patients who develop graft- versus-host disease (an activation of the donor T cells against the recipient) relapse less frequently than those patients who do not develop the disease; and 3) white cell infusions from the donor can induce remissions of the cancer after a relapse from an allogeneic BMT.
Recent studies demonstrate that donor cells can 'take' (engraft) much lower doses of chemotherapy with or without radiation that have significantly less toxicity compared to standard BMT. Therefore, a patient who is not eligible for the standard allogeneic BMT because of advanced age or poor medical condition may be more safely treated using a mini-BMT. The 'mini-BMT’ will hopefully capitalize on the graft-versus-tumor anti-cancer effect with initial engraftment of the donor white cells. However, if the patients engraft, subsequent donor white cell infusions are built in the protocol to maximize the graft-versus-tumor effect. Early results with mini-BMT demonstrates encouraging results, especially in CML, CLL, MDS, and multiple myeloma. |
