Pediatrics Hematology/Oncology

Understanding Bone Marrow Transplants

What is bone marrow?

Bone marrow is found inside the bone. It is the spongy part where blood cells are made. Blood cells are needed by the body to help it stay healthy. All types of blood cells are made in the bone marrow including: 
 

• Red Blood Cells (RBCs): Red blood cells carry oxygen to the body's oxygen and tissues. 
   
• White blood cells (WBCs): White blood cells are part of the immune system. This means they help fight infections. 
   
• Platelets (Plts): Platelets help blood to clot. When you have a nosebleed or a cut on the skin, platelets help control or stop the bleeding. Bone marrow is able to make the correct number of each type of blood cell. All blood cells start as a single cell called the stem cell. Stem cells can grow into all the different types of blood cells needed by your body.

What is a bone marrow transplant?

A bone marrow transplant (BMT) occurs when new bone marrow replaces a patient's old bone marrow. The new bone marrow may come from a person that is not related to the patient. It may also come from a brother or sister or from a parent. Sometimes the new bone marrow comes from the patient's own bone marrow. The new bone marrow is taken or harvested from the hipbones or from peripheral blood stem cells. A bone marrow transplant is not a surgery like a liver, heart, or lung transplant. It is when the old marrow is destroyed and killed by high doses of chemotherapy and/or radiation therapy. This is followed by a transfusion or replacement with new marrow.

Why is a bone marrow transplant needed?

A bone marrow transplant is used to cure many types of cancers, blood disorders or immune deficiencies. Some children's bodies can no longer make normal bone marrow. This means the bone marrow makes an increased number, decreased number or abnormal type of blood cells. Bone marrow transplants are also used to cure solid tumors such as Ewings sarcoma, Hodgkins lymphoma or non-Hodgkins lymphoma.

What types of bone marrow transplants are there?

There are three types of bone marrow transplants used for children today. These include:

 

• Allogeneic ("all-oh-je-nee-ik") For this type of BMT, another person provides bone marrow for the patient. The patient first has treatment called preconditioning. This treatment works to destroy the abnormal or cancer cells in the bone marrow and in the body. This is done to create room in which the new bone marrow can grow. 
   
• Autologous ("o-tol-a-gus") For an autologous BMT, the patient's own bone marrow or peripheral blood stem cells (PBSC) are used. The PBSC or bone marrow may be harvested months before the patient needs a bone marrow transplant. Therefore, the cells are frozen until they are needed. When it is time for the transplant, your child will first receive treatment to destroy the cancer cells. Because the bone marrow cannot recover from this treatment, the cells are reinfused to help rescue their bone marrow. 
   
• Cord blood After a baby is born, stem cells from the placenta and umbilical cord are collected. This is known as cord blood. Cord blood is frozen and stored until it is ready to be used by a patient. Just as in other types of bone marrow transplants, preconditioning must occur before a cord blood BMT is done.