If successful engraftment takes place without the development of GVHD, there is no need for permanent immunosuppressive therapy. The transplantation involves aspiration of bone marrow cells from multiple sites while the donor is under general anesthesia. The cells are strained to remove potentially embolic material before 400 to 800 ml is infused intravenously into the recipient, with appropriate attention to prevention of circulatory overload. In the case of genetic disorders such as thalassemia major, eradication of the patient's bone marrow is required, and busulfan may be added. For the treatment of acute leukemias, intensive chemotherapy directed at producing a remission is generally needed before bone marrow transplantation is considered.
Postoperative outcome depends on the disease being treated.
In patients who have aplastic anemia, bone marrow transplantation usually results in some form of chimerism in which both host and donor cells are in evidence. In contrast, patients being treated for acute leukemias receive much more intense cytotoxic therapy and irradiation, which results in eradication of native marrow. Successful engraftment in these cases requires that all hematopoietic and immune cells subsequently expressed by the recipient, including plasma cells and macrophages, be derived from the donor. Patients remain severely immunocompromised for four to five months after transplantation, even though in vitro tests of immune function return to normal earlier. In the absence of GVHD or with syngeneic grafts, immunologic recovery eventually takes place.