Bone marrow transplants
The technique of using normal bone marrow to replace malignant (cancerous) or defective marrow in a patient 1. Bone marrow found in a normal adult can be either red or yellow in colour. The marrow used in transplants is red, and is found in bone with significant marrow space – hip bones, upper leg (femur), etc.. Some of these bones are easier to access and contain more bone marrow than others.
There are two basic types of bone marrow transplant :
- Allogeneic : a donor is chosen who has bone marrow tissue very similar to that of the patient’s. Usually this involves the siblings or a close relative to the patient. The donor provides some of his marrow to the patient by way of surgery. If a twin sibling volunteers to donate his/her marrow to the patient, this is known as a syngeneic transplant. These are often very successful (providing the twins are identical ) as the genetic make-up of twins is very similar.
- Autologous : involves the use of the patient’s own bone marrow, which is then transplanted to a different site.
Reasons for bone marrow transplantation
Bone marrow transplants are carried out the following disorders 2 :
- Some types of severe anaemias.
- Leukaemia. (cancer of the white blood cells)
- Errors of the metabolism.
Why is it done
A bone marrow transplant is carried out on a patient who has a potentially fatal blood or immune system disorder. It is best performed in a hospital ward equipped to handle patients with acute leukaemias 3.
The professionals handling a bone marrow transplant may include:
- Oncologist – a cancer specialist.
- Haematologist – blood and blood cell specialist.
- Radiotherapist – x-ray treatment specialist.
- Microbiologist – bacteria/ virus / fungi specialist
- Immunologist – specialist in the bodies defense mechanism.
- Lab services – analysing special reports.
A bone marrow transplant is usually carried out in the following sequence :
Allogeneic process :
- A suitable donor is chosen. For each sibling that the patient has, there is a 25% chance of finding a compatible donor. Blood samples are taken from both the donor and the recipient. These are then compared to assess the compatibility between the two tissues.
- All the bone marrow in the recipient is destroyed by treatment with either cytotoxic drugs or radiotherapy. This ensures that all diseased cells in the marrow (including cancer cells) are destroyed. Destroying the bone marrow of the recipient also prevents rejection of the donated cells. Care must be taken at this time because the recipient is at a great risk of infection, due to the loss of his immune functions. Thus he or she must be kept in a single room with reverse isolation facilities.
- The donor is placed under general anaesthesia (put to sleep) and bone marrow is aspirated (sucked out) from the donors sternum (middle chest bone) and/or iliac crest (hip bone). Only 20-50ml of fluid volume is necessary as the transplanted cells grow quickly and occupy the bone spaces of the recipient.