What is Bone marrow?
Bone marrow is the flexible tissue which is present in the hollow interior of bones. Bone marrow transplantation (BMT) is a medical procedure that involves the transplantation of blood stem cells derived from the bone marrow. Bone marrow transplantation is often known as hematopoietic stem cell transplantation (HSCT). In the fields of hematology and oncology, this medical procedure is most often performed for people with diseases of the blood, bone marrow, or certain types of cancer.
The main goal of BMT is to transfer healthy bone marrow cells into a person after the elimination of his/her own unhealthy bone marrow. A procedure of bone marrow transplant involves taking stem cells from the bone marrow, filtering those cells, and providing them back either to the patient or to another person. Yet, bone marrow transplantation is not a standard treatment therapy but it has been used effectively to treat diseases such as leukemias, lymphomas, aplastic anemia, immune deficiency disorders, and some solid tumor cancers since 1968.
Bone marrow is the soft and spongy tissue which is present inside the bones. Bone marrow is the one medium for growth and storage of about 95 percent of the body’s blood cells. Blood cells which are produced, called stem cells. Bone marrow is a vital part of the body as it is the body’s main blood cell “factory.” A person can become very ill or even die if something is wrong with the marrow.
Why bone marrow transplant is necessary?
The bone marrow is unhealthy in certain diseases like leukemia and aplastic anemia. A bone marrow transplant may be required when a person’s bone marrow has been damaged or destroyed because of a disease or intense treatments of radiation or chemotherapy for cancer. To put healthy stem cells instead of the unhealthy ones is the main goal of a bone marrow transplant. This can be helpful to treat or even cure the disease.
A bone marrow transplant can be used,
- To replace the bone marrow and refurbish its normal function after high doses of chemotherapy or radiation are given to treat a malignancy. This process is often called “rescue” (for diseases such as lymphoma, neuroblastoma, and breast cancer).
- To replace bone marrow with genetically healthy functioning bone marrow to stop further damage from a genetic disease process (such as Hurler’s syndrome, and adrenoleukodystrophy).
- To replace diseased or non-functioning bone marrow with healthy functioning bone marrow for the conditions like leukemia, aplastic anemia, and sickle cell anemia.
Types of Bone Marrow Transplants:
Depending on the donor, bone marrow transplants are of different types as follows:
Autologous bone marrow transplant:
In this type of transplant, the donor is the person him/herself. For this, the stem cells are taken from the patient either by bone marrow harvest or apheresis (peripheral blood stem cells). Then, these stem cells are given back to the patient after intensive treatment. The term “rescue” is often used instead of “transplant.”
Allogeneic bone marrow transplant:
In this type of transplant, the donor is another person who has the same genetic type as the patient needing the transplant (recipient). As, the tissues are inherited, it is more probable that the recipient will find a suitable donor in a brother or sister. But, this takes place only in 25 to 30 percent of the time. By bone marrow harvest or apheresis (peripheral blood stem cells), the stem cells are taken from a genetically-matched donor.
For allogeneic bone marrow transplants, following donors are included:
- A parent: when the donor is a parent a haploid-identical is match and the genetic match is at least half identical to the receiver.
- An identical twin:An allogeneic transplant from an identical twin is a syngeneic transplant. For a bone marrow transplant, identical twins are believed a complete genetic match.
- Unrelated bone marrow transplants (UBMT or MUD for matched unrelated donor): A bone marrow transplant from an unrelated donor who has the genetically matched marrow or stem cells. With the help of the national bone marrow registries, unrelated donors are founded.
Umbilical cord blood transplant:
After delivery of an infant, immediately stem cells are taken from an umbilical cord. These stem cells replicate into mature, functioning blood cells faster and more successfully than do stem cells taken from the bone marrow of another child or adult. Before the transplantation is carried out, the stem cells are tested, typed, counted, and frozen.
Sources of Bone Marrow Stem Cells:
- Apheresis: Collecting stem cells by filtering the blood for peripheral (circulating) blood cells (PBSC)
- Bone marrow harvest: Collecting stem cells by taking them directly out of the bone
- Umbilical cord blood: Stem cells are filtered from blood in the umbilical cord after a baby is born
Apheresis method has better results for both the donor and the recipient and so the majority of marrow stem cell transplants are made using this method.
How are a donor and recipient matched?
Human leukocyte antigen (HLA) tissue types are involved in matching of a donor and recipient. The genetic make-up of a person’s immune system can be dogged by the antigens on the surface of these special white blood cells. At least 100 HLA antigens are present in human body. But, to determine the matching of a donor and recipient few major antigens are matched. The others are believed as “minor” and their effect on a successful transplant is not as well defined.
The playing role all antigens in the process of a bone marrow transplant is still investigated by medical research. With the more matching of antigens, the engraftment of donated marrow will become better.
The bone marrow transplant procedure:
Bone marrow transplant preparations are vary depending on,
- The type of transplant
- The disease requiring transplant
- Your tolerance for certain medications
Following points are also considered:
- In the preparations, most time high doses of chemotherapy and/or radiation are included. This intense therapy is carried out to successfully treat the malignancy and create room in the bone marrow for the growth of new cells. This therapy is often referred as ablative, or myeloablative, due to the effect on the bone marrow. All the blood cells in our body are produced by the bone marrow. This process of cell production is stopped by Ablative therapy and the marrow becomes empty. An empty marrow is required to create room for the new stem cells to grow and ascertain a new production system.
- Following the administration of the chemotherapy and/or radiation, the marrow transplant is given into the bloodstream through the central venous catheter. To place the marrow into the bone is not a surgical procedure but it is analogous to receiving a blood transfusion. Into the bone marrow, the stem cells find their way and start to reproduce and establish new, healthy blood cells.
- To prevent and treat infections, side effects of treatments, and complications, supportive care is also given. Supportive treatments incorporate frequent blood tests, close monitoring of vital signs, strict measurement of input and output, daily weigh-ins, and supplying a protected and sterile environment.
The days before transplant are calculated as minus days and the day of transplant is considered day zero. After the transplantation, engraftment and recovery are counted as plus days. For instance, a patient may come in the hospital on day -8 for preparative regimen. The day of transplant is numbered zero. Days +1, +2, etc., will follow. With each day before, during, and after transplant, specific events, complications, and risks are also related. To understand by the patient and family where they are in terms of risks and discharge planning, the numbering of the days is helpful.
The patient may experience the following during the infusion of bone marrow:
- Chest pain
After the infusion of bone marrow, the patient may:
- be very susceptible to infection
- have blood transfusions
- be confined to a sterile environment
- take multiple antibiotics and other medications
- undergo continual laboratory testing
- experience excessive bleeding
- spend several weeks in the hospital
- experience nausea, vomiting, diarrhea, mouth sores, and extreme weakness
- experience temporary mental confusion and emotional or psychological distress
- be given medication to prevent graft-versus-host disease – if the transplantation was allogeneic. The transplanted new cells (the graft), tend to attack the patient’s tissues (the host), even though the donor is a relative, such as a brother, sister, or parent.
The recovery process is also continues for several months or longer after leaving the hospital. During this time the patient cannot return to work or many previously enjoyed activities. The patient must also take recurrent follow-up visits to the hospital or physician’s office for check-up.
Engraftment is the process that happens to donor marrow or stem cells after their entry in the donor recipient’s body. It takes place when the donated cells make their way to the marrow and begin reproducing new blood cells. Engraftment generally takes place around day +15 or +30 depending on the type of transplant and the disease being treated. During the days following transplant, blood counts will be performed regularly to assess instigation and progress of engraftment. Delaying in engraftment can occurs due to infection, medications, low donated stem cell count, or graft failure. For the entire immune system to fully recover, the new bone marrow may begin making cells in the first 30 days following transplant, it may take months, even years.
Complications and side effects may occur following BMT:
Depending on the following, complications may vary.
- Age and overall health of the recipient
- Type of marrow transplant
- Presence of severe complications
- Type of disease requiring transplant
- Variance of tissue matching between donor and recipient
- Preparative regimen
Each individual may experience symptoms differently. With bone marrow transplantation, following complications may occur alone, or in combination:
- Infections like bacterial, viral or fungal. Viral and fungal infections can be life threatening.
- Low platelets and low red blood cells
- Pain related to mouth sores and gastrointestinal (GI) irritation is common.
- Fluid overload, a complication can lead to pneumonia, liver damage, and high blood pressure.
- Respiratory distress
- Damage of organ like liver and heart
- Graft-versus-host disease (GVHD)
Long-term outlook for bone marrow transplantation:
Prognosis greatly depends on the type of marrow transplant, type and extent of the disease being treated, disease response to treatment, genetics, your age and overall health, your tolerance of specific medications, procedures, or therapies, and severity of complications.
For bone marrow transplant, prognosis, and long-term survival can vary greatly from person to person same as with any other procedure. For an increased number of diseases, the number of transplants occurring and medical developments has greatly enhanced the outcome for bone marrow transplant in children and adults. Following a bone marrow transplant, constant follow-up care is important for the patient. New methods are continually being discovered to improve treatment and to reduce complications and side effects of a bone marrow transplant.