2. Identify a source of marrow stem cells . 
     Once the decision to have a transplant is made, the possibility of your being able to use your own marrow
     cells or blood stem cells has to be evaluated. If your bone marrow is extensively involved by tumor , an
     allogeneic or syngeneic transplant or peripheral stem cell transplant will be the only choices. A bone marrow
     donor will have to be found—an HLA-matched brother or sister or a partially matched relative for an
     allogeneic transplant , a matched but unrelated donor for an allogeneic transplant or an identical twin for a
     syngeneic transplant—or it must be confirmed that there are no tumor cells circulating in your blood.
         Allogeneic transplantation is more effective in younger people. The incidence of graft-versus-host disease
     rises rapidly in those over 30, occurring most often in people older than 40 to 55.

3. Administer high-dose chemotherapy—with or without radiotherapy—to kill 
    the cancer and, in an allogeneic transplant, destroy your own immune system .
     The purpose of the high-dose therapy is to destroy the cancer, suppress the immune system if necessary
     and empty the marrow to provide space for the new bone marrow cells to grow. If an allogeneic transplant is
     being performed, your own immune system must be destroyed. If it isn't, your immune cells will reject the
     donor's bone marrow cells and leave you without a functioning bone marrow.