Harvesting Stem Cells

As I continue to read and learn, I keep running into the idea of harvesting stem cells with the idea of holding them in a freezer for an eventual bone marrow transplant.  The purpose would be to flush out all the diseased cells, and replace them with new, healthy cells.  (Actually, the stem cells will grow into healthy cells.)  The harvesting is done after a course of treatment has diminished the disease.  I asked Dr. Treon about this, and he said they don't recommend it, because there is a 10% mortality rate with an autologous transplantation (meaning you put your own, previously harvested cells back), and a 50% mortality rate if you use someone else's (almost always a very close relative).