Bone Marrow Transplant
The soft, gelatinous tissue filling the medullary cavities at the centers of bones containing immature cells called the stem cells is known as the Bone Marrow. There are two types of bone marrow, Yellow Bone Marrow also known as Fatty Tissue and Red Bone Marrow also known as Myeloid Tissue. The majority of red blood cells, platelets, and most of the white blood cells are formed in the red marrow while only a few of them are formed in the yellow marrow.
Bone Marrow is important for:
- Circulatory System
- Red Blood Cells
- White Blood Cells
- Lymphatic System
- Immune System
Why is Bone Marrow Transplant Needed?
The goal of a bone marrow transplant is to cure many diseases and types of cancer. When the doses of chemotherapy or radiation needed to cure a cancer are so high that a person’s bone marrow stem cells will be permanently damaged or destroyed by the treatment, a bone marrow transplant may be needed. Bone marrow transplants may also be needed if the bone marrow has been destroyed by a disease.
What are some diseases that may benefit from bone marrow transplant? The following diseases are the ones that most commonly benefit from bone marrow transplant:
- Severe aplastic anemia
- Multiple myeloma
- Immune deficiency disorders
- Some solid-tumor cancers
However, patients experience diseases differently, and bone marrow transplant may not be appropriate for everyone who suffers from these diseases.
What are the different procedures for Bone Marrow Transplant?
1) Autologous transplantation – This procedure involves using the patient’s own blood cells provided they are suitable. Stem cells are collected directly from the bloodstream. While stem cells normally live in our marrow, a combination of chemotherapy and a growth factor (a drug that stimulates stem cells) called Granulocyte Colony Stimulating Factor (G-CSF) is used to expand the number of stem cells in the marrow and cause them to spill out into the circulating blood. From herethrough a special machine called a cell separator, they can be collected from a vein by passing the blood, similar to dialysis. This machine separates and collects the stem cells and returns the rest of the blood to the patient. The stem cells are then processed, frozen and stored until the scheduled transplant.
Before the transplant, the patient will be be given very high dose chemotherapy for and sometimes radiotherapy if needed, to destroy the underlying disease. This is called conditioning therapy. After this, the stem cells are thawed and reinfused through a vein into the patient’s blood stream, similar to a blood transfusion. After that, the stem cells make their way to the bone marrow where they become re-established and start making new blood cells.
2) Allogeneic transplantation – This procedurere places damaged or destroyed bone marrow stem cells with healthy ones from a donor. The “allo” prefix means “other”, meaning that healthy cells are taken from someone.A related donor is often a brother or sister with the same tissue type as the patient. A parent’s cells may be used if there is a close match. When no relatives are available, the cells may come from a volunteer donor. Once identified, the donor will undergo tissue typing, also called human leukocyte antigen (HLA) matching. HLAs are markers the body uses to decide if a “foreign” substance belongs in the body or should be destroyed. When marrow or stem cells are rejected, the body attacks its own tissues in a process known as graft-versus-host disease (GVHD). Also, before stem cells are collected from blood or bone marrow, the donor must undergo a thorough physical exam and blood testing for hepatitis viruses, human immunodeficiency disease (HIV) and other infectious agents or viruses.
The most common source of stem cells for transplant is peripheral blood that flows throughout our veins and arteries.
The blood is removed from the donor and the cells collected using a process called apheresis, which involves placing a needle in the donor’s vein, usually in the arm, similar to administering a blood test. The donor’s blood is pumped through an apheresis machine, which separates the blood into four components: red cells, plasma, white cells and platelets. The white cells and platelets, which contain the stem cells, are collected, while the red cells and plasma are returned to the donor. It can take one to two sessions of apheresis to collect enough blood from a MUD.
If enough stem cells can’t be retrieved from apheresis, they can be removed directly from the bone marrow. This requires the donor to undergo a minor outpatient surgical procedure. While the donor is under anesthesia, the surgeon inserts a hollow needle into the donor’s pelvic bones just below the waist and removes liquid marrow. This is done a number of times until several pints of marrow are collected. The donor’s body naturally replaces the marrow soon after the procedure. The marrow that’s removed (harvested) passes through a series of filters to remove bone or tissue fragments and is then placed in a plastic bag from which it can be infused into the recipient’s vein. The marrow is usually given to the patient within a few hours and almost always within 24 hours. If necessary, however, marrow can be frozen and stored and will remain suitable for use for years.
A rich source of stem cells for blood cancer patients are the stored stem cells collected from the umbilical cord and placenta after a baby is born, called the cord blood unit. Parents may choose to have the cord blood unit collected after delivery. Healthy parents with healthy children and no transplant candidate in the family can choose to donate their newborn’s cord blood to cord blood banks or research programs at participating hospitals. Parents with a child or a family member who could be a candidate for transplantation should discuss with their doctor the potential benefits of saving their newborn’s cord blood for possible family use.
As part of conditioning, the patient will be given a range of medicines which involves a tube to be inserted into a large vein near the heart of the patient. This is known as a central line and is used instead of many (often painful) injections.The conditioning process involves using high doses of chemotherapy and sometimes radiation.
It’s carried out for three reasons:
- a) to destroy the existing bone marrow cells to make room for the transplanted tissue
- b) to destroy any existing cancer cells
- c) to stop your immune system working, which reduces the risk of the transplant being rejected
The conditioning process usually takes between four and seven days.
The first stage of the recovery process involves waiting for the stem cells to reach the bone marrow and start producing new blood cells. This is known as engraftment and usually occurs 15-30 days after the transplant takes place. During this period, the patient will need to have regular blood transfusions, as he’ll have a low number of red blood cells.
The risk of developing an infection will also be increased, because the patientwill have a low number of