<qa>  What is the most effective treatment regimen in treating chronic phase chronic myelogenous leukRATIONALE: Giving chemotherapy before a donor bone marrow transplant helps stop the growth of cancer cells. It also helps stop the patients immune system from rejecting the donors stem cells. Also, imatinib mesylate may stop the growth of cancer cells by blocking the enzymes needed for cancer cell growth. Interferon alfa may interfere with the growth of cancer cells and slow the growth of cancer. When the healthy stem cells from a donor are infused into the patient they may help the patients bone marrow make stem cells, red blood cells, white blood cells, and platelets. It is not yet known which treatment regimen is most effective in treating chronic phase chronic myelogenous leukemia. 