Bone Marrow Transplantation in Children
What is a bone marrow transplant?
Bone marrow transplantation (BMT) is a special therapy for patients with certain cancers or other diseases. A bone marrow transplant involves taking cells that are normally found in the bone marrow (stem cells), filtering those cells, and giving them back either to the patient they were taken from or to another person. The goal of BMT is to transfuse healthy bone marrow cells into a person after his or her own unhealthy bone marrow has been eliminated.
What is bone marrow?
The bone marrow is a soft, spongy tissue found inside the bones. The bone marrow in the hips, breast bone, spine, ribs, and skull contain cells that produce the body's blood cells. The bone marrow is responsible for the development and storage of most of the body's blood cells. The three main types of blood cells produced in the bone marrow include:
Red blood cells (erythrocytes) - carry oxygen to the tissues in the body
White blood cells (leukocytes) - help fight infections and to aid in the immune system
Platelets - help with blood clotting
Each of these cells carries a life-maintaining function. The bone marrow is a vital part of the human body.
What are stem cells?
Every type of blood cell in the bone marrow begins as a stem cell. Stem cells are immature cells that are able to produce other blood cells that mature and function as needed.
Stem cells are the most important cells needed in a bone marrow transplant. Stem cells, when transplanted, find their way to the recipient's marrow and begin to differentiate and produce all types of blood cells that are needed by the body.
Why is a bone marrow transplant needed?
The goal of a bone marrow transplant is to cure many diseases and certain types of cancer. When a child's bone marrow has been damaged or destroyed due to a disease or intense treatments of radiation or chemotherapy for cancer, a bone marrow transplant may be needed.
A bone marrow transplant can be used to:
Replace diseased, non-functioning bone marrow with healthy functioning bone marrow (for conditions such as leukemia, aplastic anemia, and sickle cell anemia)
Replace the bone marrow and restore its normal function after high doses of chemotherapy or radiation are given to treat cancer. This process is often called "rescue" (for diseases such as lymphoma and neuroblastoma)
Replace bone marrow with genetically healthy functioning bone marrow to prevent further damage from a genetic disease process (such as Hurler's syndrome and adrenoleukodystrophy disorder)
Bone marrow transplant has risks involved, some of which are life threatening. The risks and benefits must be weighed in a thorough discussion with the bone marrow transplant team prior to the procedure.
Each child experiences diseases differently and a bone marrow transplant may not be appropriate for everyone who suffers from these diseases. Some of the diseases that have been treated with bone marrow transplant include the following:
Some solid tumors (i.e., neuroblastoma, rhabdomyosarcoma, brain tumors)
Immune deficiencies (severe combined immunodeficiency disorder, Wiskott-Aldrich syndrome)
Sickle cell disease
Metabolic/storage diseases (i.e., Hurler's syndrome, adrenoleukodystrophy disorder)
Cancer of the kidneys
What are the different types of bone marrow transplants?
There are different types of bone marrow transplants depending on who the donor is. The different types of bone marrow transplant include the following:
Autologous bone marrow transplant
The donor is the child him/herself. Stem cells are taken from the child either by bone marrow harvest or apheresis (a process of collecting peripheral blood stem cells) and then given back to the child after intensive treatment. Sometimes the term "rescue" is used instead of "transplant."
Allogeneic bone marrow transplant
The donor shares the same (or similar) genetic type as the child. Stem cells are taken either by bone marrow harvest or apheresis from a genetically-matched donor, often a brother or sister. Other donors for allogeneic bone marrow transplants may include:
A parent - a haploid-identical match is when the donor is a parent and the genetic match is at least half identical to the recipient. Unfortunately, parents may not be a good enough match to be donors in many cases.
Unrelated bone marrow transplants (or MUD for matched unrelated donor) - the genetically matched marrow or stem cells are from an unrelated donor. Unrelated donors are found through the national bone marrow registries.
Umbilical cord blood transplant
Stem cells are taken from an umbilical cord immediately after delivery of an infant. These stem cells reproduce into mature, functioning blood cells quicker and more effectively than do stem cells taken from the bone marrow of another child or adult. The stem cells are tested, typed, counted, and frozen until they are needed for a transplant.
Because the stem cells are "new," they are able to produce more blood cells from each stem cell. Another advantage cord blood has is that the T-lymphocytes (part of the immune system that causes a transplant-related problem called graft-versus-host disease) are not completely functional this early. Recipients of cord blood transplants have a decreased risk for severe graft-versus-host disease.
The bone marrow transplant team
The group of specialists involved in the care of children who are undergoing a transplant procedure is often referred to as the "transplant team." Each individual works together to provide the best chance for a successful transplant. The bone marrow transplant team consists of:
Physicians - physicians who specialize in oncology, hematology, immunology, and bone marrow transplantation
Transplant nurse coordinator - a nurse who organizes all aspects of care provided to your child before and after the transplant. The nurse coordinator will provide patient education and coordinate the diagnostic testing and follow-up care.
Social workers - professionals who will provide support to your family and help your family deal with many issues that may arise, including lodging and transportation, finances, and legal issues. They can also help coordinate alternative means for school, so that your child does not get behind.
Dietitians - professionals who will help your child meet his/her nutritional needs before and after the transplant. They will work closely with you and your family.
Physical therapists - professionals who will help your child become strong and independent with movement and endurance after the transplantation
Pastoral care - chaplains who provide spiritual care and support
Other team members - several other team members will evaluate your child before transplantation and will provide follow-up care, as needed. These include, but are not limited to, the following:
An extensive evaluation is completed by the bone marrow transplant team. The decision for your child to undergo a bone marrow transplant will be based on many factors including:
Your child's age, overall health, and medical history
Extent of the disease
Availability of a donor
Your child's tolerance for specific medications, procedures, or therapies
Expectations for the course of the disease
Expectations for the course of the transplant
Your opinion or preference
Preparation for the recipient
For the child receiving the transplant, the following will occur in advance of the procedure:
Prior to the transplant, an extensive evaluation is completed by the bone marrow transplant team. All other treatment options are discussed and evaluated for risk-versus-benefit.
A complete medical history and physical examination are performed, including multiple tests to evaluate the child's blood and organ functions (i.e., heart, kidney, liver, lungs).
A child will often come into the transplant center up to 10 days prior to transplant for hydration, evaluation, and other preparations. A catheter, also called a central venous line, is surgically placed in a vein in the chest area. Blood products and medications will be administered through the catheter.
A suitable (tissue typed and matched) donor must be available. Finding a matching donor can be a challenging and lengthy process. Voluntary marrow donors are registered in several national and international registries. A bone marrow search involves searching these registries for donors whose blood most closely resembles or matches the child needing the transplant.
Preparation for the donor
Donor sources available include: self, sibling, parent or relative, non-related person, or umbilical cord blood from a related or non-related person. There are national and international registries for non-related persons and cord blood. Family member may be tested for a match (typed) because of the desire to help. These relatives may or may not elect to have their type registered for use with other recipients.
If the potential donor is notified that they may be a match for a child needing a transplant, they will undergo additional tests. Tests related to their health, exposure to viruses, and complete genetic analysis will be done to determine the extent of the match. The donor will be given instructions on how a bone marrow donation will be made.
Once a match for a child needing a bone marrow transplant is found, then stem cells will be collected either by a bone marrow harvest (collection of stem cells with a needle placed into the soft center of the bone marrow) or peripheral blood stem cell collection (stem cells are collected from the circulating cells in the blood). Of the two, peripheral blood stem cell donations are now more common. Cord blood has already been collected at the time of a birth and stored for later use.
How are a donor and recipient matched?
Matching involves typing human leukocyte antigen (HLA) tissue. The antigens on the surface of these special white blood cells determine the genetic make-up of a person's immune system. There are at least 100 HLA antigens, however, it is believed that there are a few major antigens that determine whether a donor and recipient match. The others are considered "minor" and their effect on a successful transplant is not as well defined.
Medical research is still investigating the role all antigens play in the process of a bone marrow transplant. The more antigens that match, the better the engraftment of donated marrow. Engraftment of the stem cells occurs when the donated cells make their way to the marrow and begin reproducing new blood cells.
How are the stem cells collected?
A bone marrow transplant is done by transferring stem cells from one person to another. Stem cells can either be collected from the circulating cells in the blood (the peripheral system) or from the bone marrow.
Peripheral blood stem cells (PBSCs)
Peripheral blood stem cells (PBSCs) are collected by an apheresis, a process in which the donor is connected to a special cell separation machine via a needle inserted in the vein. Blood is taken from one vein and is circulated though the machine which removes the stem cells and returns the remaining blood and plasma back to the donor through another needle inserted into the opposite arm. Several sessions may be required to collect enough stem cells to assure a chance of successful engraftment in the recipient.
A medication may be given to the donor for about one week prior to apheresis that will stimulate the bone marrow to increase production of new stem cells. These new stem cells will be released from the marrow and into the circulating or peripheral blood system.
Bone marrow harvest
Bone marrow harvesting involves collecting stem cells with a needle placed into the soft center of the bone, the marrow. Most sites used for bone marrow harvesting are located in the hip bones and the sternum. The procedure takes place in the operating room. The donor will be anesthetized during the harvest and will not feel the needle. In recovery, the donor may experience some pain in the areas where the needle was inserted.
If the donor is the child him/herself, it is called an autologous bone marrow transplant. If an autologous transplant is planned, previously collected stem cells from either peripheral (apheresis) or harvest, are counted, screened, and ready to infuse.
Umbilical cord blood
For umbilical cord blood transplants, blood has been collected at the time of a birth and stored. Cord blood is collected after delivery, when the placenta and umbilical cord are separated from the infant. The site of collection is cleaned to prevent bacteria from entering the collection process. The blood that is contained in the cord is collected in a sterile container. The blood is then tested for type and the presence of viruses or disease, and the stem cells are counted. The cord blood is then stored in special freezers and is registered in a national registry for potential recipient matches.
The bone marrow transplant procedure
The preparations for a bone marrow transplant vary depending on the type of transplant, the disease requiring transplant, and your child's tolerance for certain medications. Consider the following:
Most often, high doses of chemotherapy and/or radiation are included in the preparations. This intense therapy is required to effectively treat the malignancy and make room in the bone marrow for the new cells to grow. This therapy is often called ablative, or myeloablative, because of the effect on the bone marrow. The bone marrow produces most of the blood cells in our body. Ablative therapy prevents this process of cell production and the marrow becomes empty. An empty marrow is needed to make room for the new stem cells to grow and establish a new production system.
After the chemotherapy and/or radiation is administered, the transplant, either from bone marrow, cord, or from peripherally collected stem cells, is given through the central venous catheter into the bloodstream. It is not a surgical procedure to place the marrow into the bone, but is similar to receiving a blood transfusion. The stem cells find their way into the bone marrow and begin reproducing and establishing new, healthy blood cells.
Supportive care is given to prevent and treat infections, side effects of treatments, and complications. This includes frequent blood tests, close monitoring of vital signs, strict measurement of input and output, weighing your child daily (or twice daily), and providing a protected and clean environment.
The days before transplant are counted as minus days. The day of transplant is considered day 0. Engraftment and recovery following the transplant are counted as plus days. For example, a child may enter the hospital on day -8 for preparative regimen. Days +1, +2, etc., will follow the transplant. There are specific possible events, complications, and risks associated with each day before, during, and after transplant. The days are numbered to help the child and family understand where they are in terms of risks and discharge planning.
During actual infusion of the bone marrow, your child may experience any, or all, of the following symptoms:
After infusion, your child may:
Spend several weeks in the hospital
Be very susceptible to infection
Experience excessive bleeding
Need blood transfusions
Be confined to a very clean environment to minimize the chance of infection
Take multiple antibiotics and other medications
Be given medication to prevent graft-versus-host disease (if the transplant was allogeneic). The transplanted new cells (the graft) tend to attack the child's tissues (the host), even if the donor is a relative, such as a brother, sister, or parent.
Undergo continual laboratory testing
Experience nausea, vomiting, diarrhea, mouth sores, and extreme weakness
Experience temporary emotional or psychological distress
Your child's physical and mental health are important in the success of a transplant. Every measure is taken to minimize complications and promote a healthy, happy, safe environment for your child.
When does engraftment occur?
Engraftment of the stem cells occurs when the donated cells make their way to the marrow and begin producing new blood cells. Depending on the type of transplant and the disease being treated, engraftment usually occurs between day +15 and +30. Blood counts will be performed frequently during the days following transplant to evaluate initiation and progress of engraftment. Platelets are generally the last blood cell to recover.
Engraftment can be delayed because of infection, medications, low donated stem cell count, or graft failure. Although the new bone marrow may begin making cells in the first 30 days following transplant, it may take months, even years, for the entire immune system to fully recover.
What complications and side effects may occur following BMT?
The following are complications that may occur with a bone marrow transplant. However, each child may experience symptoms differently. Complications may vary depending on the following:
Type of marrow transplant
Type of disease requiring transplant
Age and overall health of the recipient
Variance of tissue matching between donor and recipient
Presence of severe complications
Possible complications may include, but are not limited to, the following. These complications may also occur alone, or in combination:
Infections are likely in the child with severe bone marrow suppression. Bacterial infections are the most common. Viral and fungal infections can be life threatening. Any infection can cause an extended hospital stay, prevent or delay engraftment, and/or cause permanent organ damage. Antibiotics, anti-fungal medications, and anti-viral medications are often given to prevent serious infection in the immunosuppressed child.
Preventative measures for common sources of infection are also a part of transplant. This may include any or all of the following:
Blood tests are performed to prevent, detect, and treat infections. Often, multiple antibiotics are started if an infection is suspected.
Low platelets and low red blood cells
Thrombocytopenia (low platelets) and anemia (low red blood cells), as a result of a non-functioning bone marrow, can be dangerous and even life threatening. Most children will require multiple blood product transfusions. Low platelets can cause dangerous bleeding in the lungs, gastrointestinal (GI) tract, and brain.
Pain related to mouth sores and gastrointestinal (GI) irritation is common. High doses of chemotherapy and radiation can cause severe mucositis (inflammation of the mouth and GI tract). Without the normal immune system functioning, your child is unable to heal these irritations quickly. Often, pain medication is required. Mouth care is needed to prevent infection and injury when mucositis is suspected.
Diarrhea, nausea, and vomiting may occur with chemotherapy, radiation, and/or GI irritation. Calories and proteins may be given through an intravenous (IV) line until your child is able to eat again and the diarrhea has resolved.
Fluid overload is a complication that can lead to pneumonia, liver damage, and high blood pressure. The primary reason for fluid overload is because the kidneys cannot keep up with the large amount of fluid being given intravenously in the form of medications, nutrition, and blood products. The kidneys may also be damaged from disease, infection, chemotherapy, radiation, and/or antibiotics.
During transplant and recovery, your child will be assessed for signs and symptoms of fluid overload. He/she may be weighed at least daily, often twice or three times daily, and blood chemistries and input and output will be measured frequently. Medications that help kidney function and elimination of excess fluid may be given.
Respiratory status is an important function that may be compromised during transplant. Infection, inflammation of the airway, fluid overload, graft-versus-host disease, and bleeding are all potential life-threatening complications that may occur in the lungs and pulmonary system. Supplemental oxygen may be needed to help your child breathe better until problems are corrected.
Close monitoring of your child's respiratory status may include:
Chest X-rays - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film
Pulse oximetry - an oximeter is a small machine that measures the amount of oxygen in the blood. To obtain this measurement, a small sensor that looks like a Band-Aid® is taped onto a finger or toe. When the machine is on, a small red light can be seen in the sensor. The sensor is painless and the red light does not get hot.
The liver and heart are important organs that may be damaged during the transplant process. Temporary or permanent damage to the liver and heart may be caused by infection, graft-versus-host disease, high doses of chemotherapy and radiation, or fluid overload.
Close monitoring of your child's blood work and vital signs is important in minimizing and detecting any organ damage that has occurred.
Failure of the graft (transplant) taking hold in the marrow is a potential complication. Graft failure may occur as a result of infection, recurrent disease, or if the stem cell count of the donated marrow was insufficient to cause engraftment.
Graft failure may be treated with an additional marrow transplant if a source is available.
Graft-versus-host disease (GVHD) can be a serious and life-threatening complication of a bone marrow transplant. GVHD occurs when the donor's immune system reacts against the recipient's tissue. The new cells do not recognize the tissues and organs of the recipient's body. The most common sites for GVHD are the GI tract, liver, skin, and lungs.
GVHD is graded from I to IV and can be acute (occurs suddenly) or chronic (occurs over a period of time). Your child will be monitored closely for signs and symptoms of GVHD. Diarrhea, fever, rash, skin changes, abdominal pain, respiratory complications, and decreased liver function may be present with GVHD.
Medications will be given prior to transplant to reduce the risk of this complication.
When will my child be discharged?
When your child is discharged following a bone marrow transplant depends on many factors, including the following:
Extent of engraftment
Presence of complications
Your child's overall health
Distance from the facility (This may be specified by your child's team of physicians. Occasionally, a bone marrow transplant patient will be required to stay within a certain distance or travel time from the facility to ensure safety if complications arise.)
Frequent visits to your child's transplant team will be required after discharge to determine effectiveness of treatment, detect complications, detect recurrent disease, and to manage the late effects associated with a bone marrow transplant. The frequency and duration of visits will be determined by your child's transplant team.
Long-term outlook for a bone marrow transplantation
Prognosis greatly depends on the following:
Type of marrow transplant
Type and extent of the disease being treated
Disease response to treatment
Age and overall health of the child
Your child's tolerance of specific medications, procedures, or therapies
Severity of complications
As with any procedure, such as bone marrow transplant, prognosis, and long-term survival can vary greatly from child to child. The number of transplants being done for an increased number of diseases and ongoing medical developments have greatly improved the outcome for bone marrow transplant in children and adults. Continuous follow-up care is essential for the child following a bone marrow transplant. New methods to improve treatment and decrease complications and side effects of a transplant are continually being discovered.