Bone marrow transplants may be used as part of the treatment of a number of different types of cancer, although they are most often used for leukaemias or lymphomas.

Bone marrow transplants may use tissue donated by someone else (an allogeneic transplant) or use the patient's own bone marrow (an autologous transplant).

Allogeneic transplants can usually only be done if there is a close relative (normally a brother or sister) whose bone marrow closely matches the patient's own marrow. Occasionally an unrelated donor can be used if their white blood cells are a very good match.

The first stage of an allogeneic bone marrow transplant is to destroy the patient's own marrow completely. This is done with high doses of chemotherapy, often combined with radiotherapy. After this the bone marrow cells from the donor are given through a drip into a vein.

The new marrow cells take a few weeks to settle into the bones and start producing new blood cells. During this time people are normally kept in hospital and nursed in a room on their own because their immunity is low and they are at risk of getting infections. Often antibiotics will be given during this time as well as blood transfusions. There will be some dietary restrictions (such as avoiding raw or reheated foods that could contain bacteria) and family and friends will be asked not to visit if they have infections.

During the six months after the transplant frequent check ups will be done. This is partly to look for any sign of remaining leukaemia cells and also to look for any signs of the new marrow reacting against your own body tissue (this is called graft-versus-host disease). Symptoms of graft-versus-host disease include diarrhoea, skin rashes and jaundice. Normally drugs will be prescribed after the transplant to try and prevent graft-versus-host disease developing.

When an autologous transplant is done, using the patient's own marrow, the first stage of the process is to collect the bone marrow. This is done under a general anaesthetic. To collect the marrow needles are inserted into the bone in several different places and samples of the marrow, which is quite liquid, are sucked out by syringes. After this the process is similar to an allogeneic transplant, with high dose chemotherapy (and radiotherapy) followed by an infusion of the stored marrow. Once again a period of intensive monitoring and support is needed while the marrow settles in and starts to take effect. This time, however, as the patient's own marrow has been used graft-versus-host disease is not a problem.

In recent years stem cell transplants have offered an alternative to bone marrow transplants for some people. Stem cells are the basic cell in the marrow which produces the various blood cells. Nowadays injections of a special protein, called a growth factor, can be given which causes the marrow to make an excessive number of stem cells. These then spill out into the blood and can be collected. Although stem cell transplants may also be either autologous (using the patients own stem cells) or allogeneic (using stem cells from a donor) the great majority are autologous transplants.