One aspect the investigators, in Ottawa, have focused on is the initial intensive conditioning regimen, specifically the radiation component. It is the investigators belief that in the most resistant disease it is important to use the highest tolerable anti-leukemic treatment upfront, specifically, enhancing the radiation component of the initial conditioning regimen. Previous studies have suggested that higher doses of radiation might be more effective at eliminating the disease, however, toxicity and logistics of delivering the radiation have limited its use. Technical advances in the delivery of radiation have now permitted the safer use of high doses of radiation.