What is bone marrow transplantation - what is bone marrow transplant for donor
Bone marrow transplantation is a procedure in which bone marrow cells are taken out from a donor and given to a patient.
Depending on the donor or source of bone marrow, different types of bone marrow transplantation is done.
There are two major ways in which bone marrow cells can be removed from a person or donor. The first is by taking the bone marrow cells directly from the marrow using long needles (called bone marrow harvest needles) to suck out the marrow from the marrow spaces at the large hipbone. This is done under anaesthesia over about 2 hours. The second is a revolutionary method, which have been available only in the last 5-10 years. By giving certain medications, the bone marrow cells can be stimulated to circulate from the marrow into the blood. Using a special machine called an apheresis machine ( also called a cell separator), the cells can be removed from the blood. Blood is drawn out as in a blood donation, into the machine, which then separates out the marrow cells and return blood cells to the donor.
The donor is usually a relative, usually either a brother or sister. However, there are three other sources. They are unrelated match donor, cord blood and autologous.
Unrelated donors are donors that have volunteered to donate bone marrow just like blood donors.
Cord blood is obtained from the cord of newborn babies. It may be used for transplantation of a relative or be used for non-related recipients.
It is also possible for the patient to donate his own marrow cells to be stored first and then returned to him after the chemotherapy has been given as conditioning.
(See autologous BMT section)
What is bone marrow transplant
Figure 22b: Sources of haemopoeitic stem cells for transplantation
Sibling (Brother and sisters) This is commonest form in the allogeneic setting.
Twin An identical twin shares the same ‘marrow type’ as the patient, thus making it very safe.
Extended family Sometimes a family member may share the same ‘marrow type’ as the patient and can donate to the patient.
Unrelated donors Volunteer donors who have the same ‘marrow type’ are able to donate their marrow for needy patients.
Autologous The patient’s own marrow can be used to do a transplant. (See chapter on autologous transplantation)
Thus the different types of transplants are:
Allogeneic bone marrow transplantation Allogeneic peripheral stem cell transplantation Autologous bone marrow transplantation Autologous peripheral stem cell transplantation Cord blood transplantation.
Who should receive a bone marrow transplant?
There are three important conditions limiting the use of bone marrow transplantation:
(i) Age - The older the patient, the more risky the transplant because of a higher incidence of complications. The upper age limit of transplants locally is currently 40 years of age. In some overseas centres, the upper age limit is 55 years of age.
(ii) Suitable disease - Bone marrow transplantation is not suitable for all blood diseases. The results are best for acute myeloid leukaemia if the transplant is done only when the patient has achieved remission. In chronic myeloid leukaemia the results are best when the transplant is performed relatively early i.e. when the patient is still in the chronic phase of the disease. In severe aplastic anaemia, new marrow is required to replace the patient's marrow that has completely failed.
(iii) Suitable donor - Allogeneic bone marrow transplants require a donor with the same tissue type as the patient. There is no age limit for donors. However the donor must be healthy and has not transmissible diseases.
How to find a suitable donor?
Our immune system which protects us from bacteria, viruses and other microorganisms which try to invade our bodies, has to have a way of identifying which cells are our own and which cells (micro-organisms) are ‘enemies’ that has to be destroyed. They are able to recognise our own cells because the cells have antigens (markers) on their surfaces. The antigens that we know are called HLA antigens. (HLA stands for human leucocyte antigens.) An analogy can be made. In war we can recognise each other by the uniforms or badges we wear. The enemy wears different uniforms and thus are easily recognised and attacked. We will not attack our own soldiers who are wearing the same uniforms.
These HLA antigens are unique in that they differ in us from one another. Family members tend to share same antigens. Brothers and sisters have a high chance of having the same antigens.
The process in which we check to see what antigens are carried on our cells is called tissue typing. Thus we are able to find out one’s tissue type using this process. This process is also called ‘HLA typing’.
What is bone marrow transplantation
How is tissue typing done?
A bone marrow test is not required. Only blood is needed because the white cells (mainly lymphocytes) that is in our blood is used. A blood sample is taken and using sophisticated tests the tissue type is determined.
In Malaysia, tissue typing is performed by the Institute of Medical Research, Kuala Lumpur and recently in University Hospital, Kuala Lumpur. Singapore is the nearest centre where this is also done. Only blood samples in special bottles need to be sent and the donors and patients do not need to go to the centres themselves.
The chance of finding a suitable donor is best from a brother or a sister of the patient. There is a one in four chance of a brother or a sister having a complete match. The chances of the rest of the family (parents or children) having the same tissue type are much less (about one in 100). This is because genes inherited from
both parents of the patient determine the tissue or HLA type. The same tissue type is thus most likely to be found among the patient’s brothers and sisters (siblings).
Different ethnic groups have different HLA types just like hair color or facial features.
Thus if it is more likely to find the same tissue type in persons of the same ethnicity.
Figure 23a: Inheritance of HLA antigens
There are four possibilities for the type of HLA inherited from parents. They are inherited in pairs. We obtain one of the pairs from each parent. Thus the chances of having a sibling with the same tissue type is about 25%.
What is bone marrow transplantation
What are the problems associated with bone marrow transplants?
Sterility - the inability to have children is a permanent side effect of bone marrow transplantation. The ability to participate in sexual activity is not affected. In overseas centres, sperm banking is an option for male patients. Also eggs may also be stored for the female.
Skin changes and hair loss- the hair loss is only temporary and the hair will grow back after the transplant but sometimes is a bit thinner than previously. There are skin changes due to the chemotherapy given for the transplant but these are also temporary.
Mucositis - during the transplant, most patients develop a very sore mouth from the chemotherapy and for a while, cannot eat and will depend on nutrition given intravenously. Pain relieve can be achieved usually with medication.
Graft-versus-host-disease - this is a special complication of transplants due to the immune cells (lymphocytes) from the donor present in the donated marrow, which attack the recipient (patient). This is because they recognise the patient’s body cells as foreign like bacteria or micro-organisms. This occurs more often in HLA
mismatched transplants and unrelated donor transplants. It can also occur in fully matched transplants because there are still antigens that we yet cannot tissue type.
Also they may be other factors that change the donated cells resulting in them not recognising the shared HLA antigens as shared.
It can cause rashes, liver damage and damage to the gut. It occurs in about 40% of patients but can usually be treated. It is occasionally fatal.
Infections - During and after transplants, the patient remains at high risk of infections and will be on antibiotics and special medication for about one year. The immunity does not return to normal for a few years.
What does the patient undergo?
Because the procedure is very tedious and also difficult, the donor is counselled at length and allowed to make his or her own mind to go ahead with the transplantation.
The transplant patient is hospitalised for about one month but will require very close follow up at least three times a week for the subsequent two months. During the hospitalisation, a special device called a Hickman catheter is placed (using minor surgery) which serves as a way of giving fluids, chemotherapy, blood transfusion and nutrition directly into the bloodstream. This eliminates the need to use veins on
the arms to take blood samples and give intravenous medication.
The patient undergoes conditioning chemotherapy to prepare the patient to receive the new marrow. Conditioning chemotherapy has side effects including vomiting, diarrhoea and occasional bleeding from the bladder. The new marrow collected from the donor is then transfused into the patient. These cells know how to get to the bone marrow spaces through the bloodstream in a normal process called homing. The blood counts of the patient remain very low for about 2 to 3 weeks before the new marrow grows. The patient will be required to take medications for at least a year.
What does the donor undergo?
The donor is counselled (given advice) about the procedure and how it is useful for the patient. As the procedure is completely voluntary, the donor’s wishes are highly respected.
Depending on the procedure to be used whether conventional bone marrow harvest or peripheral stem cell collection, the donor is selected.
In the conventional bone marrow harvest programmes, the donor undergoes a medical examination to determine fitness for surgery. A unit of blood may be taken a week prior to the harvest and given back to the donor at the time of harvest so as to minimise the need for additional blood transfusion. The harvest is done under general anaesthesia and marrow is aspirated using special needles from the back of the pelvis (hip bone). There is no permanent side effect and the main complication is some discomfort felt at the back for several days after the procedure. The donor is usually hospitalised for three days only.
what is bone marrow transplant for - what is bone marrow transplant for donor - what is bone marrow transplant like
