As well as enabling doctors to use high dose chemotherapy, SCT can play an important role in the cure of leukaemia through an effect known as graft versus leukaemia (GvL). In GvL, immune cells contained in the graft attack leukaemic cells remaining in the patient’s body. This makes SCT a very important treatment option for children for whom chemotherapy has failed.
Allogeneic stem cell transplantation is a high-risk procedure. Its use is usually restricted to children who have relapsed early in their treatment for leukaemia, or who have suffered more than one relapse.
In order to minimise the risk of complications, it is necessary to find a donor whose tissue type matches the patient’s as closely as possible. The preferred donor is a sibling with a closely matched tissue type. The next best choice is a matched family member. If not available, a matched unrelated donor will be sought from the national bone marrow register.
Transplants contain functioning cells from the donor’s immune system. This gives the patient important protection because their own immune system has been destroyed in preparation for the transplant. It also promotes GvL.
However, there is a risk that the immune cells will recognise the patient’s cells as foreign and attack them. This is called graft versus host disease (GvHD). Closely matching the tissue types of the donor and the patient minimises the risk of GvHD.