Bone Marrow Transplant For Children

Bone marrow is a spongy, fatty, and soft tissue that is in the centre of the bones. It contains countless blood vessels and blood-filled spaces. The two types of bone marrow (yellow, red) are present inside the centre regions of most bones in the body. Bone marrow contains the critical blood stem cells that continuously produce mature blood cells such as red blood cells (RBCs), white blood cells (WBCs), and platelets. This process of continuous ongoing blood cell production is called haematopoiesis, and is critical for life. Stem cells are primitive cells and have the capacity to indefinitely renew themselves. These are present inside the bone marrow. They evolve into mature blood cells. But, when diseases impact bone marrow, it’s unable to function correctly. For instance, a child with a genetic disease like sickle cell disease (SCD) or thalassemia will have malfunctioning bone marrow.

What is Bone Marrow Transplant?

A Bone Marrow Transplant (BMT) is a medical procedure where damaged, diseased, or non-functioning bone marrow is swapped with healthy bone marrow. The “healthy” bone marrow contains healthy stem cells with the potential for growth and production of normal blood cells (unlike sickle cells or cancerous cells). Doctors take the donor’s healthy blood-producing stem cells and insert them inside the patient’s bloodstream. Once the healthy bone marrow is inside the patient’s bloodstream, the stem cells go to the recipient’s bone marrow to settle and start growing and producing healthy blood cells.

Different Sources of Obtaining Bone Marrow For Transplant

The stem cells can be obtained directly from the bone marrow when it is called a bone marrow transplant (BMT).
It can also be obtained from the blood after diving some mobilizing agents to the donor when it is called peripheral blood stem cell collection (PBSC) transplant or Apheresis.
The stem cells can also be collected from the umbilical cord and placenta when it is called cord blood transplant (CBT)

Whichever way stem cells are collected the underlying principles are the same. The term Haematopoietic stem cell transplant (HSCT) encompasses all the different types of transplants. For the purposes of this article, we will use the term BMT henceforth.

Different Applications For Bone Marrow Transplant

BMT is a common treatment option for thousands of children across the world with different types of cancer. Children with blood cancers like lymphoma, leukaemia, etc., in particular, receive this treatment especially when the first-line treatment is not being effective. It is also the treatment of choice for curative options in many non-cancerous conditions where the bone marrow is either not working or malfunctioning like aplastic anaemia, thalassaemia, sickle cell anaemia, many primary immunodeficiencies, autoimmune conditions, and some metabolic disorders. The goal of BMT is to save their lives. Replacing their diseased bone marrow with healthy bone marrow can make all the difference. It can enable their bodies to produce healthy RBCs, WBCs, and platelets once again.

The stem cells collected from the donors (called “grafts”) are filtered and sometimes manipulated and put into the patient’s bloodstream via tubes called IV catheters. Children have to receive strong chemotherapy doses before the BMT to ensure that the recipient does not kill the incoming donor cells. The chemotherapy also kills the diseased stem cells in the bone marrow, making way for the healthy bone marrow stem cells.

[Read : Primary Immunodeficiency in Children]

List of Reasons For Which Child Receive BMT

Thousands of children receive this treatment every month around the world mainly for the following reasons:

1. Cancer Chemotherapy Alone Cannot Eradicate the Disease

A child may receive high doses of radiation therapy and chemotherapy. Still, traces of cancer remain in some cases. Sometimes, the speed of response is such that there is a very high chance of cancer returning after stopping the chemotherapy. Giving the stem cell back during transplant allows the doctors to administer high doses of chemotherapy which would be otherwise not possible and, in some cancers, the new donor-derived immune system will keep attacking cancer so that it does not recur again.

2. Replace Non-Functioning or Non-Functioning Bone Marrow

Children with conditions like thalassaemia, SCD, aplastic anaemia, etc., don’t have fully-functioning bone marrow. Their diseased, malfunctioning bone marrow is replaced with healthy, effective bone marrow in the transplant.

3. Immune System Regeneration

Some children are born with defects in the immune system. These defects cannot be medications, Such children do have a tendency to develop severe and unusual infections and die early without treatment. In some other children, the immune system is malfunctioning and attacking their own body. BMT can help with immune system regeneration in such cases. Once their bone marrow resumes the production of healthy WBCs, RBCs, and platelets, their immune systems grow stronger.

4. Treat Genetic Diseases Where the Body is Not Able to Make Some Proteins

Some genetic disorders like adrenoleukodystrophy or Hurler’s syndrome are incurable without BMT. Children with such disorders are typically unable to produce certain enzymes which are necessary for the healthy maintenance of the body. If these children are able to have normal blood cells which can produce what is missing in their body, then the body starts functioning normally. Giving these children genetically healthy and fully-functional bone marrow is the last resort.

The rate of BMT success for children is high in comparison to adults. Still, doctors weigh the risks and benefits of this process very carefully before recommending it to children.

Types of Bone Marrow Transplant For Children

BMTs are divided into different categories based on who the donor of the bone marrow is. They are:

1. Autologous BMT

Cells that are obtained from one’s own body are called “autologous.” In autologous BMTs, the child themselves is a donor. Doctors collect the child’s stem cells usually via a process called peripheral blood stem cell collection. The doctors then freeze these stem cells. The child receives intensive treatment (e.g., chemotherapy). Then, the harvested blood stem cells are given back to the child so that the child’s body is able to recover from the high-dose chemotherapy. Autologous BMTs are commonly known as “bone marrow rescue” procedures.

2. Allogeneic BMT

In these procedures, the donor and the child are different individuals. Donor and the recipient undergo tests for a match of their cell type. Doctors do this by looking at a type of marker on the cell surface called Human Leukocyte Antigens (HLA antigens). The process of looking at the tissue markers is called HLA typing. A parent/sibling may be the donor. With the current modern techniques, we can even perform transplants using partially matched family donors, called haploidentical stem cell transplants. The blood stem cells of donors are collected via direct bone marrow harvesting or peripheral blood stem cell harvesting. They’re then placed inside the bloodstream of the diseased child. This type of BMT is the rarest.

3. Unrelated BMT

As the name suggests, the donors in these BMTs are not related to the children. Doctors review national bone marrow registries to find HLA-matched (but unrelated) donors.

[Read : Importance of Umbilical Cord and Placenta During Pregnancy]

4. Umbilical Cord Transplant

The placentas of pregnant women are rich sources of blood stem cells. They are collected via the umbilical cord. That’s why many doctors (with the donor’s permission) collect stem cells from the umbilical cords of newborns. These stem cells are frozen. When doctors receive requests for BMTs, they review the frozen stem cells to find potential matches.

There are two ways of collecting blood stem cells from donors:

a) Bone Marrow Harvesting

Donors are placed under general anaesthesia, and their bone marrow is collected directly from their hip bones.

b) Leukapheresis or PBSC collection

This method of stem cell extraction is mainly used to treat children suffering from leukaemia. The donors are given injections for a few days prior to the collection of stem cells. These medicines transport their underdeveloped stem cells from their bone marrow and into their bloodstream. The blood is then collected from the donor via IV lines. A machine is used to isolate the WBCs that contain the stem cells. The stem cells are later given to the child.

Why and When Children Need Bone Marrow Transplants?

Children’s bone marrow holds their hematopoietic cells (stem cells), which grow to become

RBCs to disperse oxygen across the body.
WBCs to fight infections and assist the immune system.
Platelets to form blood clots and prevent excessive bleeding or blood loss.

Children with conditions like leukaemia, SCD, lymphoma, neuroblastoma, and other types of cancers or genetic diseases have diseased bone marrow. The hematopoietic cells in their bone marrow can’t produce healthy blood products or the bone marrow replaces abnormal cancer cells which do not allow normal cells to multiplyRReplacing the non-functioning or malfunctioning hematopoietic cells is critical for the child’s survival. Children who experience such conditions, diseases, or situations are given BMTs.

Diseases That Can be Treated With BMT

BMTs are complex medical procedures that carry many risks, some of which are potentially life-threatening. Healthcare providers collaborate with specialized BMT teams before deciding whether or not the child will benefit from the procedure. The risks and benefits of BMTs are assessed very carefully in each individual situation. This procedure is mainly recommended for the following diseases and conditions:

1. Cancers

Blood cancers like leukaemia, multiple myeloma, Hodgkin’s or non-Hodgkin’s lymphoma. Many of these blood cancers can only be permanently cured with BMTs if they have not responded well to the initial treatment. The same applies to kidney cancers, neuroblastoma, rhabdomyosarcoma, and malignant brain tumors when routine chemotherapy is not expected to result in a permanent cure.

2. Genetic Diseases

Congenital immune deficiencies, sickle cell disease, osteopetrosis thalassemia, Wiscott Aldrich syndrome, and other genetic disorders.

3. Bone Marrow Failure Conditions

When the bone marrow fails to function due to

4. Metabolic conditions

Children with metabolic conditions such as Hurler syndrome, adrenoleukodystrophy disorder]respond well to BMTs if performed early in the course of the illness. Rarely some severe cases of autoimmune diseases (for instance, systemic lupus erythematosus) may also require BMT.

[Read : Stem Cells Uses, Importance, and Potential Medical Applications]

Risks and Complications of Bone Marrow Transplant For Children

The success rate, risks, and complications of BMT depend on a lot of factors, including:

The child’s age
The child’s present health conditions
The types of treatments or procedures the child has undergone in the past
How the previous treatments (if any) have affected the child’s disease/condition
The child’s ability to tolerate the procedures that precede and follow BMT
Whether the child has pre-existing health complications
The type of BMT being performed
The type of disease/condition the BMT is treating
The types of medications the child is allowed to take(many medicines are administered before BMT)
The degree of tissue match between the child and the donor

BMTs have cured thousands of children of their diseases and genetic conditions. Although doctors are constantly finding new ways to make BMTs safer, these transplants are still far from being risk-free. Parents and children struggling with emotional issues regarding the transplant should seek support from doctors, BMT experts, and support groups.

More importantly, they should know the main risks that come with BMTs. Here are all the possible complications that can arise before, during, or after BMTs –

1. Pain

Children often experience gastrointestinal (GI) irritation when undergoing chemotherapy and radiation therapy before the BMT. These irritations may cause them to develop painful mouth sores.

2. Infections

As a result of chemotherapy used in preparation for transplant and time taken for new stem cells to produce mature cells and a lowered immune system infections may arise.

3. Respiratory Problems

Lung problems may arise due to internal infections, inflammation of respiratory airways, or diseases received from the donor. Children experiencing fluid overloads and bleeding on top of serious respiratory issues will need additional oxygen support.

4. Diarrhoea

Children can experience severe bouts of diarrhoea accompanied by nausea and vomiting while receiving pre-BMT chemotherapy. These are side-effects of gastrointestinal irritations. If the child cannot eat (due to diarrhoea), doctors may feed them via IV catheters.

5. Thrombocytopenia

The child may not produce healthy levels of platelets after the transplant. Children with thrombocytopenia require multiple blood product transfusions. Sometimes bleeding can occur due to low platelets

6. Anaemia

The child may not produce healthy levels of red blood cells after the transplant. Children with anaemia also require multiple blood product transfusions.

7. Fluid Overload

Children undergoing BMT receive large amounts of IV fluids. Their kidneys may struggle to handle this excess fluid. That’s why children’s weight, urine, and blood undergo regular testing during and after BMTs.

8. Graft Failure

The donor’s cells (transplanted cells) may not mature in the child’s marrow. Children who experience graft failures require additional BMTs. Graft failures can happen due to infections, the strong and sensitised immune system of the recipient, insufficient chemotherapy pre-transplant, or regeneration of the child’s existing disease or condition.

9. Fertility Issues

The strong doses of chemotherapy/radiation before BMTs can negatively affect children’s future fertility.

10. Graft-Versus-Host Disease

GVHD is when the donor’s WBCs attack the child’s healthy cells. This is a serious complication if mild can be controlled well with medications and if severe can become life-threatening. Doctors will take various measures to reduce the risk of this complication.

In some rare cases, children may experience temporary, lasting organ damage.

How Can Parents Help Children Prepare for BMTs?

Doctors prepare children for BMTs by examining their hearts, kidneys, lungs, and other core organs. These tests reveal potential complication risks. This preparation period may take two to three days. Parents need to prepare for weeks before the BMT. They have to:

1. Give Children the Right Tests

Children undergoing BMTs require many tests. They include – bone marrow studies, echocardiograms, electrocardiograms, chest X-rays, dental checks, audiology tests, lung function tests, GFR (Glomerular Filtration Rate) tests, chest CT scans, and various blood tests. If the donor is a parent or a sibling, he or she may also have to undergo these tests.

2. Fertility Preservation

Partner with fertility preservation experts to explore the idea of preserving fertility.

3. Conditioning

Children have to check into the clinic/hospital 7-15 days before their transplants. During this period, doctors carry out a process “conditioning.” Make sure your child goes through this procedure. This process readies your child for the donor stem cell infusion.

4. Honesty

It’s natural for children undergoing BMT to have questions about the procedure. Honesty regarding details like whether the transplant may hurt, when the children can return to school, etc., is vital.

What Happens During a BMT for a Child?

Once the doctor harvests the suitable stem cells

The child receives high doses of chemotherapy/radiation which destroys their existing bone marrow. This process is called conditioning.
Next is infusion. The doctor will infuse stem cells into the child via IVs. This procedure is similar to receiving blood transfusions.
After infusion, the doctor will check the child for infection risks, bleeding, diarrhoea, and other complications. Some children may have to spend several weeks at the hospital to eliminate every complication risk.
Post BMT, children have to take antibiotics and other drugs. Patients may require blood transfusions and platelet transfusions. All BMT recipients have to take daily blood tests in the immediate post-transplant period to assess the rate of “engraftment” and monitor for complications Engraftment (the transplanted marrow starts producing new blood cells) may take 15-30 days.
Post BMT follow-up post-discharge: After discharge from the BMT unit BMT physicians will closely follow up with the patients in the outpatients’ ward. The first 3 months post-transplant will be the most critical time period where close medical attention will be necessary.

FAQ’s

1. Is it Safe to Donate Bone Marrow?

Yes. Donating bone marrow won’t shorten your life. Donors rarely experience any long-term side effects. That’s because only 1-5% of their marrow is extracted.

2. Can Infants Receive BMT?

Yes. Infants have significantly lower risks of regimen-related mortality. Allogeneic BMT can be performed on infants with blood cancers or genetic disorders.