Sign in 
The key is identifying a donor quickly and a related sample is preferred.
Matching a donor to a patient in cases of bone marrow transplantation is a complex process that is dependent on many factors, including the disease being treated and the stage of the disease. Increased survival rates have been correlated with early treatments. Therefore it is VERY important to identify a donor quickly.
In the cases of blood cancer there must be a balance found between eradicating the disease and preventing rejection of the donor cells. The donor cells have the ability to seek out and destroy the cancer cells that are missed by chemotherapy and radiation treatment. This is most effective if the donor cells recognize the patient’s cells as ‘foreign’, which occurs if tissue matching is not perfect. In some cases, it is preferred that the donor and recipient are not a perfect (100%) match. The ‘down-side’ to this is that the disparity between donor and patient will increase the chance of graft rejection and the attack of the patient’s healthy cells by the donor cells (graft versus host disease). During the transplant process doctors try to balance the benefits against the possible harm by using immunosuppression medication during the bone marrow transplant procedure.
Although there are generalized guidelines for choosing a donor, specific requirements are decided by the transplant team. In general, a related donor is considered optimal. This is why a match is usually sought within the family first. A family banked umbilical cord blood unit (UCB) would be the same as a family bone marrow unit. One of the reasons for looking in a family first is that there are also minor proteins (minor HLA) that are important and matching these can lead to increased overall survival. These minor proteins are more common within a family. Although success with unrelated is improving and in some cases survival rates are similar, the preference is for a family member donation.
There are many studies that indicate that related donors are better than unrelated, but it is important to note that an unrelated donor is better than no donor and improved HLA typing has increased survival rates from unrelated sources. One recent paper showed that 3-year overall survival in chronic lymphoid leukemia (CLL) patients was higher with related-matched donors versus unrelated-matched donors. A second study indicated that even a mismatched related donor should be considered because of the easy and rapid access to relatives and lower costs makes this a valid option.