Stem Cell Transplant Complications: Graft Failure
The first three and half months following a stem cell transplant pose the greatest risk of developing complications associated with a stem cell transplant (whether bone marrow or cord blood). However, the risk of developing stem cell transplant complications varies and depends on several factors. Among these potential stem cell transplant complications is graft failure, which is more likely to occur in some cases than others. The risk of graft failure often depends on the patient’s medical state prior to a stem cell transplant, the type of stem cell transplant performed, and the type of treatable disease involved.
What is Graft Failure?
High-dose chemotherapy which accompanies a stem cell transplant destroys the ability for bone marrow to produce white blood cells, red blood cells and platelets. Graft failure is a condition in which normal bone marrow function does not return following a stem cell transplant.
Following transplant, the graft may fail to grow in the patients’ body, which will result in bone marrow failure and the absence of new blood cell production. This can lead to side effects such as repeated infections, anemia, bruising and bleeding.
In general, doctors define graft failure as the absence of engraftment forty-two days following a stem cell transplant. In other words, the body does not accept the donated cells; however, total graft failure is considered to be rare.
Graft Failure vs. GVHD
Graft failure and graft-versus-host disease (GVHD) represent two different types of potential complications following a stem cell transplant. In the case of GVHD, the patient’s immune system will respond adversely to the donated stem cells, and white blood cells will begin to destroy the transplanted graft. This differs from the body’s failure to accept the graft and restore blood cell production that occurs in graft failure.
GVHD is a potential side effect associated with allogeneic stem cell transplants, in which stem cells are derived from a donor source such as cord blood. In the case of autologous stem cell transplants – in which the patient’s own stem cells are infused into the body – there is generally no risk of GVHD. However, the risk of graft failure following an autologous stem cell transplant is 5%.
Graft Failure Risks
There are a number of factors that may contribute to the risk of graft failure in patients undergoing a stem cell transplant. Factors that may contribute to an increased risk of graft failure include the following:
- patients with extensive marrow fibrosis prior to transplant
- viral illness
- use of certain drugs such as methotrexate
- patient age
- type of transplant (allogeneic vs autologous stem cell transplant)
- type of treatable disease
The type pf disease being treated may play a role in the risk of developing graft failure. For example, one study found that the risk of graft failure was much higher (33%) in patients undergoing a stem cell transplant for osteoporosis than in patients being treated for leukemia. This may be due to the fact that leukemia stem cell therapy is a more established treatment procedure.
In leukemia patients, however, graft failure is usually associated with the recurrence of cancer as the leukemic cells may hinder the growth of the transplanted stem cells.
For some patients who develop graft failure, the cause of graft failure is unknown.
Graft Failure Treatment
While considered relatively rare, graft failure is a serious and ultimately fatal complication that will likely require a second stem cell transplant. Stem cells used in the second transplant may be derived from either the same donor source or a different stem cell source. In patients undergoing an umbilical cord blood stem cells transplant, the same cord blood unit cannot be used. A different cord blood unit or another adult stem cell source may be used in these cases.