The marrow is the soft, fatty tissue inside bones that produces stem cells that mature into different blood cells, of which, the three main types are red blood cells, which transport oxygen; white blood cells, which combat infections; and platelets, which help stop bleeding.
A bone marrow transplant is a procedure that replaces damaged or destroyed bone marrow with healthy bone marrow stem cells.
The procedure may be recommended in certain cancers like leukaemia, lymphoma or multiple myeloma; or in diseases that affect the production of bone marrow cells like aplastic anaemia, thalassaemia or severe immune system diseases.
Different types of transplants
There are three kinds of bone marrow transplants.
An autologous transplant involves removal of bone marrow stem cells prior to chemotherapy or radiotherapy. The stem cells are stored in a freezer and after completion of the chemotherapy or radiotherapy, they are then put back into the body to produce normal blood cells.
An allogeneic transplant involves removal of bone marrow stem cells from a donor whose genes have to at least partially match that of the recipient. The donor is usually a sibling, parent, child or other blood relative. Sometimes, unrelated donors may be found through bone marrow registries.
An umbilical cord blood transplant is a type of allogeneic transplant. Stem cells removed from a newborn baby’s umbilical cord are frozen and stored until needed. As the umbilical cord blood cells are very immature, the need for matching is less. However, because the number of cells is small, it takes a longer time for normal blood cells to be produced.
Stages in transplant
There are various stages in bone marrow transplantation.
Initially, there will be an assessment of the recipient’s general health, which includes history taking, physical examination, and laboratory and imaging tests. Information will be provided on the reasons for the transplant, its benefits and risks, and the care needed after the transplant.
There will also be counselling on decisions on activities of daily living, such as payments, leave and care of family members.
Prior to the bone marrow transplant, chemotherapy, radiotherapy or both may be carried out to prepare the body for the transplant. High-dose chemotherapy, radiotherapy or both will destroy any cancer cells and all the remaining healthy bone marrow. This allows new stem cells to grow in the bone marrow.
The dose of the chemotherapy, radiotherapy or both may be reduced in older persons and those who have health problems.
The donor stem cells are collected by bone marrow harvesting of the recipient or donor; or leukapheresis. In the former, the stem cells are removed from the back of both hips under general anaesthesia. The amount removed depends on the weight of the recipient.
In the latter, the donor is given medications to promote movement of the stem cells from the marrow into the blood. The blood is then removed from the donor through an intravenous drip.
The blood cells containing the stem cells are separated, removed and given back to the recipient later. The other cells are returned to the donor.
The bone marrow transplant is usually done in a special unit in a hospital in which there are measures that reduce the likelihood of getting an infection. The transplant is carried out one to two days after completion of all preparations.
The duration of hospitalisation depends on the amount of chemotherapy or radiotherapy received, the type of procedure and the hospital’s practices.
During the hospitalisation, the recipient will be monitored with various tests and prescribed medicines that reduce the likelihood of graft versus host reaction. Blood transfusion(s) and intravenous feeding may be required.
Sometimes, some of the stages of the procedure may be carried out as an out-patient, in which case hospitalisation is not necessary. The recipient of the stem cells may get symptoms like fever, chills, decrease in blood pressure, chest pain, breathlessness, abnormal taste, and nausea.
Risks to be considered
Like all procedures, there are risks with bone marrow transplants.
A graft-versus-host disease occurs in allogeneic transplants in which the transplanted cells attack the recipient’s body cells. There may be a reduction in the number of blood cells, leading to anaemia, increased likelihood of infections and excessive bleeding.
There may be side effects from the chemotherapy, which include nausea, tiredness, hair loss and subfertility.
The likelihood of complications depends on the age and general health of the recipient; the disease for which the bone marrow transplant is being done; whether there was chemotherapy or radiotherapy prior to the transplant, and their dosages; the type of transplant (autologous, allogeneic or umbilical cord blood); and the degree to which the donor’s cells matches the recipient.
The features of the complications are variable and include anaemia; internal bleeding; venous thrombosis; infections that may be serious; pain; damage to the heart, lungs, liver and kidneys; gastrointestinal symptoms; premature menopause; delayed growth in children; and cataracts.
A bone marrow transplant may lead to a complete or partial cure of the disease.
This depends on the age and general health of the recipient; the type of cancer or disease; the type of transplant; the degree to which the donor’s cells matched the recipient; the type and dosage of chemotherapy or radiotherapy prior to the transplant; and the type of complications.
If the transplant is successful, the recipient can return to normal activities as soon as (s)he feels well.
If donated cells are transplanted, medicines would be given to the recipient to reduce the intensity of the immune response to reduce the likelihood of the body attacking the transplanted cells (immunosuppressants) or to reduce the risk of the transplanted cells attacking other cells in the recipient’s body.
It usually takes up to one year to recover fully, depending on any complications that occur. Failure of the transplant or the development of complications may lead to death.
It is vital to comply strictly with the instructions and advice of the attending doctor(s) upon discharge from the hospital. Should any problems arise at home, an early or immediate consultation with the doctor(s) would be prudent.
Bone marrow transplants are an important treatment option. While there are benefits, there are also risks from the procedure. Continuing discussions with the attending doctor will go a long way in addressing issues that may arise.