Stem cell transplantation will replace stem cells. This method is used when stem cells or bone marrow have been damaged or destroyed by the disease, including some types of cancer, or by high doses of chemotherapy or radiation therapy used to treat cancer.

Bone marrow is the soft and spongy tissue that sits inside large bones. The main task of the bone marrow is to make blood cells that circulate throughout the body. Stem cells are the most basic (basic) cells in the bone marrow, and they turn into different types of blood cells. There are two main kinds of stem cell transplants, i.e., allogeneic and autologous. During an allogeneic stem cell transplant, stem cells are taken from a person (donor) and then given to you (you are the recipient). During an autologous stem cell transplant, your own stem cells are taken. When you receive stem cells from your identical twin, this is called a syngenic transplant (isograft).


Stem cell transplantation is also called as follows:

  • bone marrow transplant, or graft, – when stem cells are taken from the bone marrow
  • graft, or transplantation, of peripheral blood stem cells (GCSSP) – when stem cells are taken from the blood
  • graft, or transplantation, of blood cells (GCS)
  • graft, or transplantation, of hematopoietic stem cells (GCSH)
  • high-dose treatment with stem cell transplant rescue


How does stem cell transplantation work

Most stem cells are encountered in the bone marrow. The stem cells that are present in the bone marrow are transformed into red blood cells, white blood cells, and platelets. When these blood cells are mature, they move into the peripheral blood (blood that circulates throughout the body). If the bone marrow has been damaged or destroyed, it cannot make normal blood cells. During a stem cell transplant, healthy stem cells are injected into your body to help your bone marrow begin functioning correctly. The new stem cells create healthy blood cells.


Why a stem cell transplant is done

A stem cell transplant may be done to treat certain cancers such as leukemia, lymphoma, multiple myeloma, and neuroblastoma. It may also be used after radiation therapy and high-dose chemotherapy that have been given to treat cancer.


When to opt for stem cell transplantation

Doctors consider some essential factors before deciding to treat cancer with stem cell transplants, including:

  • Age – Young people often tolerate stem cell transplant better and have fewer complications. Some transplant centers set an upper age limit, but this may depend on your overall health and other factors.
  • your global health and other medical conditions you have
  • the characteristics of your cancer – such as the type and stage of cancer, if you are in remission or if cancer has come back, the risk of recurrence after the transplant, and the sensitivity of cancer to chemotherapy


Types of stem cell transplants

The type of transplant is based on the person who donates the stem cells.

An autologous transplant uses stem cells from your own bone marrow or blood.

The double autograft, or a tandem transplant, consists of administering two autografts. Before each, you are given high-dose chemotherapy. Your stem cells are usually collected for the two transplants before the first chemotherapy cycle. The second transplant is usually done a few weeks to 6 months after the first.

An allogeneic transplant uses stem cells that have been collected from another person. The donor may be a relative or not.

Mini-transplant involves giving lower doses of chemotherapy and radiation before the allogeneic transplant, which can be helpful in the elderly and those with other health conditions who may not tolerate the standard transplant and its side effects. A mini-transplant is also called a reduced-intensity transplant or a non-myeloablative transplant.

Isograft uses stem cells from an identical twin.


Stem cell collection

Stem cells may be collected from a newborn’s bone marrow, peripheral blood, or umbilical cord blood.

For autologous transplantation, stem cell collection is usually done when the person is in remission and has recovered from other treatments.


Stem cells taken from the bone marrow

Bone marrow is most often collected from the hip bone since it is the body bone that contains the most marrow as well as a large number of stem cells.

Bone marrow stem cells are usually collected in the operating room under general anesthesia. A large needle inserted into the back of the hip bone is used to suck out the bone marrow. This procedure is repeated until you have enough bone marrow for the transplant. The process usually lasts from 1 to 2 hours.

A bandage is placed where the needle has entered the skin, and you will recover from anesthesia in the recovery room. The hip area may be sensitive for a few days. You may be given medication to relieve pain. The body usually replaces stem cells taken within a few weeks.

The cells collected are filtered to remove bone fragments and fat particles, then stored in bags filled with a particular solution and frozen until they are needed for transplantation.


Stem cells collected from peripheral blood

The blood usually does not contain many stem cells. Growth factors, such as plerixafor or G-CSF, may be given for a few days to encourage stem cells to grow faster and move through the blood from the bone marrow.

Blood stem cells are removed intravenously (IV). The IV is inserted into a large vein in the donor’s arm. The intravenous infusion tube is attached to a device that separates the stem cells from the blood and collects them. Once the stem cells are removed, the blood is returned to the donor. This process lasts several hours and may need to be repeated once a day for during some days to collect enough stem cells for the transplant.

The collected stem cells are filtered and then stored in bags and frozen until they are needed for the transplant.


Stem cells taken from umbilical cord blood

The newborn’s blood usually contains a large number of stem cells. After birth, blood that remains in the placenta and umbilical cord can be drawn. shortly after birth blood is collected from the umbilical cord. A device separates the stem cells from the cord blood and collects them.

The number of stem cells that must be collected from the blood of an umbilical cord is lower than that which must be taken from the bone marrow of an adult: the reason is that more blood cells can form from each stem cell of cord blood than from each stem cell of the bone marrow of the adult. The stem cells are filtered and then stored in bags and frozen.

Some cord blood banks keep stem cells in reserve for family use (private use), while others keep them for an unrelated recipient (public use).


Cord blood donation

Healthy parents expecting a child can donate blood from their child’s cord. To be eligible, parents must usually register with a cord blood bank during pregnancy. The mother may need to have blood tests before collection.

A cord blood donation may not be accepted if certain diseases affect the family or have occurred during or before pregnancy that could be transmitted through a cord blood transplant.

Some private cord blood banks may charge a fee for collection and storage.


Find a donor

To increase the chances of success of the stem cell transplant, the donor’s stem cells have to be closely compatible with the recipient’s ones. A process called HLA typing (histocompatibility antigens) ensures that the donor and recipient are as compatible as possible. There are thousands of combinations of possible tissue groups, so finding a perfectly compatible donor and recipient can be difficult.

Most compatible donors are close family members. The research for a donor begins with the recipient’s siblings since they are more likely to be compatible. If it is not possible to find a compatible donor in the family, then an unrelated donor is searched. This may seem unlikely, but finding a compatible donor unrelated to the recipient is possible.

When you want to know if a donor is compatible, they are given  blood tests and a medical exam for ensuring they are healthy. The doctor in charge of the transplant identifies possible compatible donors and organizes the analyzes for the donors.