Stem Cell Transplantation

Stem cell transplantation at a glance

• A stem cell transplant, also called a bone marrow transplant, infuses healthy blood-forming stem cells into a patient’s body to replace stem cells that have been damaged by disease, chemotherapy or radiation.
• Chemotherapy and radiation cancer treatments, which quickly target multiplying cells, can damage healthy stem cells while killing cancer cells.
• Blood-forming stem cells, which – similar to cancer cells – multiply rapidly and are found in bone marrow, create red blood cells, white blood cells and platelets.
• Damaged stem cells can result in too few of those three types of blood cells, and that can cause serious health consequences.
• A stem cell transplant infuses healthy stem cells back into the blood stream so that the patient can continue to make his or her own blood cells.

What is stem cell transplant?

A stem cell transplant, also called a bone marrow transplant, infuses healthy blood-forming stem cells into the body to replace those damaged by disease, chemotherapy or radiation. Stem cell transplants for cancer patients are most effective when the cancer is in remission, meaning all signs of the cancer have disappeared. Stem cell transplants allow patients to begin creating their own stem cells, which increases their ability to fight infection and prevent bleeding.

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Blood-forming stem cells, located in bone marrow – the spongy, middle section of certain bones – and in the peripheral blood, create three types of blood cells.

Red blood cells, also called erythrocytes, carry oxygen from the lungs throughout the body. They also carry carbon dioxide back to the lungs to be expelled.

White blood cells, called leukocytes, help the body fight infections caused by viruses, bacteria and fungi. If the white blood cells drop below a certain level (1,000 per cubic millimeter) the body can be at risk for serious infections.

Platelets, called thrombocytes, help the blood to clot and seal damaged blood vessels. People with low platelets may bruise easily and be prone to nosebleeds and bleeding gums.

Blood stem cells are not the same as embryo stem cells, which are used in cloning and other types of research.

Prior to the transplant, the patient will be conditioned. Conditioning involves using high doses of chemo or radiation to kill all remaining cancer cells, make room in the bone marrow for the new stem cells, and suppress the immune system to reduce the chance of the patient rejecting the stem cell transplant.

Once the patient is ready to receive the stem cell transplant, he or she is hooked up to an intravenous (IV) line much like in a blood transfusion. The stem cells are infused into the patient’s blood stream and travel back to the bone marrow to make new stem cells, resulting in healthy blood cells. This process is called engraftment. The infusion process can take up to five hours to complete.

Many patients celebrate their infusion day similar to a birthday.

Stem cell transplants for cancer patients are most effective when the cancer is in remission and all signs of the cancer have disappeared. Stem cell transplants allow patients to begin creating their own stem cells, which increases their ability of fighting infection and preventing bleeding.

Why get a stem cell transplant?

A stem cell transplant may be necessary for the treatment of certain cancers, as well as for blood diseases and immune system diseases. Some types of cancer, including leukemia, neuroblastoma, multiple myeloma and lymphoma, require treatment such as chemotherapy and radiation that damage the bone marrow’s ability to produce stem cells.

A bone marrow transplant (BMT) and a peripheral blood stem cell transplant (PBSCT) are used in cancer treatment to allow for high doses of chemotherapy and radiation. Chemo and radiation attack cells that multiply quickly. Because stem cells also multiply quickly, chemo and radiation can damage those cells along with cancer cells.

Without stem cells, the patient is not able to produce new blood cells to fight infections, carry oxygen and prevent bleeding. Stem cell transplantation replaces the patient’s damaged stem cells and can restore the bone marrow’s ability to produce its own stem cells.

Types of stem cell transplants

Stem cells can be taken from the patient, an identical twin, a family member or an unknown donor. In order for the stem cell transplantation to succeed, the human leukocyte antigen (HLA), or blood protein, of the donor must be a very close match to the patient’s. The higher the number of HLA matched antigens, the lesser the chance the patient will reject the stem cells.

For this reason, doctors try to use a patient’s own stem cells as much as possible. This is called an autologous transplant. If the stem cells come from the patient, the chance of rejection is very small.

In order to use an autologous transplant, patients must have their stem cells removed, or harvested, before beginning cancer treatments, because chemotherapy and radiation can harm stem cells. The stem cells are then frozen using a process called cryopreservation, which stores them for use after cancer treatments. Once the cancer is in remission, the stem cells can be thawed and given back to the patient.

If a patient were unable to use his or her own stem cells, the best option would be to use the stem cells of an identical twin. This is called a syngeneic transplant. Syngeneic transplants are extremely rare.

Because most people do not have an identical twin, patients often use a family member’s or an unknown donor’s stem cells. This is called an allogeneic transplant. A close relative of the patient, such as a brother or sister, has the best chance of being an HLA match. According to the American Cancer Society, only about 25 to 35 percent of patients have an HLA matched sibling.

Origin of stem cells used in transplants

Oncologists turn to three sources of blood stem cells for transplant purposes.

A bone marrow transplant (BMT) refers to the process of retrieving stem cells from the bone marrow. The cells are typically taken from the pelvic bone and sometimes from the breastbone.

During a BMT the doctor extracts bone marrow, processes it to separate the stem cells from blood and bone fragments, and then cryopreserves them for later use.

A peripheral blood stem cell transplant (PBSCT) involves apheresis, which is a medical term for separation. Normally, only a small amount of stem cells are found in the blood stream. These are called peripheral blood stem cells (PBSC).

The patient will take medication for four to five days before the procedure to increase the amount of PBSC in the bloodstream. PBSCT then utilizes a special machine that separates the stem cells from the blood, which is returned to the body and the stem cells are cryopreserved for later use.

An umbilical cord blood transplant (UCBT) refers to the process of using the stem cells found in the blood of the umbilical cord, the organ that attaches the baby to the placenta during pregnancy. A large number of stem cells are normally found in the blood of newborn babies. After birth, the blood that is left behind in the placenta and umbilical cord (known as cord blood) can be taken and stored for later use in a stem cell transplant.

The cord blood is frozen until needed. A cord blood transplant uses blood that normally is thrown out after a baby is born. About 1 in 3 unrelated hematopoietic stem cell transplants are done with cord blood.

Risks and side effects of a stem cell transplant

The short-term side effects of stem cell transplantation include:

• Nausea and vomiting
• Fatigue
• Hair loss
• Mouth sores and other skin reactions.

Risks of BMT, PBSCT and UCBT include:

• Increased risk for bleeding and infection
• Anemia
• Graft versus host disease, in which the white blood cells of the donor (graft) identify the cells of the patient (host) as foreign and attack them. GVHD, a serious complication, can occur a few weeks after the transplant or much later.

Risks of donating bone marrow

The risks of donating bone marrow are minimal. Donors may have complications related to the anesthesia used during the procedure. The area from which the marrow was harvested may be sore or tender for a few days following the procedure. A doctor will discuss all risks and side effects with the donor prior to the procedure.