If you have cancer and have been found eligible for a stem cell transplant, the first step is finding whether one of your family members is a potential donor. The transplant team will make special blood studies on you and your family members to find the best tissue type match. The standard test is called tissue typing, also known as human leukocyte antigen (HLA) type. HLA are proteins found on the surface of most cells in your body and make up your tissue type (different from your blood type). You inherit these HLA proteins from both your parents. The transplant team will try to match these proteins to find your best donor. The closest the tissue type matching lowers the risk of graft-versus-host disease (GVHD) and transplant rejection from happening.
The search for a good match usually starts with your brother or sister whose chances of being a perfect match is 1 out of 4. If your sibling is not a good match, the search is then extended to your parents, half siblings, and extended family. If none of your relatives are found to be a good match, the transplant team will use the transplant registries to find the right donor for you.
For some types of cancer, an autologous transplant is possible as treatment, this means you can be your own donor by using your own marrow stem cells. In this type of transplant, you don’t have to worry about GVHD, however there is an increased risk of the cancer coming back.
If no matched stem cell donor can be found, the transplant team might consider the umbilical cord blood registries. The umbilical cord blood contains high levels of stem cells, and the advantage of using this as a source is that it doesn’t have to be a perfect tissue match with you. However only a limited number of cells can be collected and thus may not be enough for your treatment.