Kevin
The HD preperative treatment is to kill off as many cancer cells as possible, but according to the article we have been discussing, the cancer stem cells are resistant to this treatment. So even if you kill off all cancer cells, the cancer always returns because you didnt kill the stem cells. Thats the theory anyway.
Donor matches depend on HLA markers. For adult donors, most places require a match of at least 5 of these 6 HLA markers. Even this cannot eliminate GvHD, but it does reduce the possibility. The younger you are the better your chances of dealing with the chemo, the transplant and the possible GvHD.