Not to derail, but to undergo a bone marrow or stem cell transplant, many (I did) receive total body irradiation and chemo at about 10X strength to literally kill your bone marrow. When this happens, you have no red cells, thus no oxygen to your brain. No platelets, you bleed internally. No white cells, you quickly die of massive infection (as did Paul Allen R.I.P.)
At this point, the donor’s stem cells are infused into your blood stream. If they do not engraft in your marrow and begin producing blood cells, it can become life-threatening very quickly. You would then be absolutely dependent upon transfusions of red cells and IV antibiotics, anti-fungals and anti-virals to remain alive. There is a 30% mortality rate over the first three years.
So, God’s unfathomable mercy remains.