Bone Marrow Transplant (BMT)/Stem Cell Transplant (SCT)
- A BMT/SCT is the only curative option in CML but comes with considerable risks of
mortality and morbidities.
- A patient has to have a related or unrelated donor matched at 3-5 Human Leukocyte
Antigens (HLA) to undergo a successful transplant. Human Leukocyte Typing or HLA
typing is also called tissue typing. There are cells in our body which have specific
proteins called antigens and these proteins signal to our immune system to recognize the
cells as our own and not foreign. However, when our own cells are killed in a BMT, and
new donor cells are infused, these have to be exactly matched in these protein antigens.
If they are not, then 2 things can happen:
1. The host cells recognize the donor cells as "foreign" and reject the donor graft. This is
called graft rejection.
2. The donor cells recognize the host organs and tissues as "foreign" and begin attacking them
giving rise to graft versus host diseases (GVHD) which can sometimes be fatal.
- Therefore, if there is a perfect match between HLAs of donor and recipient, this will
prevent graft rejection and GVHD. There are basically 5 types of HLA: HLA-A, HLA-
B, HLA-C, HLA-DR1 and HLA-DQ1. And you get a set from both parents. So, if there
is a perfect match in all 5, it is a 10/10 match. With unrelated transplants, doctors will
look for a 10/10 match. For sibling transplants, it is fine to go with a 6/6 match at HLA-
A, HLA-B and HLA-DR1 as most antigens between siblings are inherited. It will cost
more to match at all the major AND minor antigens since a high-resolution mapping is
done. For siblings, it will cost less because a low resolution mapping is done. The more
the mismatch, the more chances of rejection and GVHD.
- Some information on how to find a perfect donor is here. High dose chemotherapy
and radiation are used to kill the host marrow and then the donor cells derived
from either the host bone marrow or blood are infused into the patient. The
donor cells engraft and kill CML cells by the graft-versus-leukemia (GVL)
effect. However, donor cells can recognize host tissues and organs as 'foreign'
and start attacking them resulting in graft-versus-host disease (GVHD).
- For older patients with donors, a mini-transplant can be recommended. This
uses low doses of chemotherapy as pre-transplant regimen with or without
radiation. This type of procedure can decrease the upfront transplant mortality
rate but can be associated with more disease relapse and GVHD. Read about
mini-transplants in Dr. Giralt's review in 2005 ASH Education Book titled
Reduced Intensity Conditioning Regimens for Hematologic Malignancies
PATIENT STORIES