A stem cell transplant, also called a bone marrow transplant, can be used to treat certain types of cancer. This procedure might be called peripheral stem cell transplant or cord blood transplant, depending on where the stem cells come from. Here we’ll explain stem cells and stem cell transplant, cover some of the issues that come with transplants, and describe what it's like to donate stem cells. All of the blood cells in your body - white blood cells, red blood cells, and platelets - start out as young (immature) cells called hematopoietic stem cells. Hematopoietic means blood-forming. These are very young cells that are not fully developed. Even though they start out the same, these stem cells can mature into any type of blood cell, depending on what the body needs when each stem cell is developing. Stem cells mostly live in the bone marrow (the spongy center of certain bones). This is where they divide to make new blood cells. Once blood cells mature, they leave the bone marrow and enter the bloodstream. A small number of the immature stem cells also get into the bloodstream. These are called peripheral blood stem cells. Bone marrow is the spongy liquid tissue in the center of some bones. It has a rich supply of stem cells, and its main job is to make blood cells that circulate in your body. The bones of the pelvis (hip) have the most marrow and contain large numbers of stem cells. For this reason, cells from the pelvic bone are used most often for a bone marrow transplant. Enough marrow must be removed to collect a large number of healthy stem cells. The bone marrow is harvested (removed) while the donor is under general anesthesia. A large needle is put through the skin on the lower back and into the back of the hip bone. The thick liquid marrow is pulled out through the needle. This is repeated until enough marrow has been taken out
There are two types of stem cell transplantation:
Autologous stem cell transplant
In an autologous stem cell or bone marrow transplant, healthy cells are harvested from the bone marrow of a patient. The harvested bone marrow is frozen and stored until it is ready for use. In the meantime, the patient undergoes a 'conditioning regimen' to prepare their body for the transplant. In this regimen, they may receive high dose chemotherapy r radiation therapy. These treatments destroy cancer cells, but they also kill bone marrow cells. This is where the transplant comes in. The patient is injected with their own stored blood stem cells. These cells 'take' to the body and restore its ability to produce blood cells.
Allogeneic stem cell transplant
An allogeneic bone marrow or stem cell transplant uses donor stem cells to treat blood cancers that affect the bone marrow, like leukemia. The cell transplants come from a donor whose tissue most closely matches that patient. The donor cells are injected after the patient has undergone chemotherapy. But beyond restoring the blood-producing ability of the body, allogeneic stem cell transplantation can help fight cancer directly. The donated cells generate a new immune response, meaning they find and kill cancer cells, sometimes better than the original immune cells of the patient. This is called the graft-versus-cancer effect, and it can help fight cancer. Unfortunately, allogeneic stem cells come with an increased risk of rejection or GVHD.
To improve the chances of the transplant being successful, donated stem cells need to carry a special genetic marker – known as a human leukocyte antigen (HLA) – that's identical or very similar to that of the person receiving the transplant. The best chance of getting a match is from a brother or sister, or sometimes another close family member. If there are no matches in your close family, a search of the British Bone Marrow Registry will be carried out. Most people will eventually find a donor in the registry, although a small number of people may find it very hard or impossible to find a suitable match. A stem cell transplant can take a few months to complete. The process begins with treatment with high doses of chemotherapy and maybe radiation therapy. This treatment goes on for a week or two. Once you have finished, you will have a few days to rest. Next, you will receive the blood stem cells. The day you receive your stem cells is often called “day zero.” The stem cells will be given to you through an intravenous (IV) catheter. This process is like receiving a blood transfusion. It takes 1 to 5 hours to receive all the stem cells. After receiving the stem cells, you begin the recovery phase. During this time, doctors will follow the progress of the new blood cells by checking your blood counts often. As the new stem cells produce blood cells, your blood counts will go up. Even after your blood counts return to normal, it takes much longer for your immune system to fully recover—several months for autologous transplants, and 1 to 2 years for allogeneic or syngeneic transplants.
A bone marrow transplant can cure some diseases and put others into remission. Goals of a bone marrow transplant depend on your condition but usually include controlling or curing your disease, extending your life, and improving your quality of life. Some people have few side effects and complications from a bone marrow transplant. Others may experience short- and long-term side effects and complications. It can be difficult to predict the severity of side effects and the success of the transplant. It can be helpful to remember that there are many people who have transplants who also experienced some very difficult days during the transplant process. But, ultimately, they had successful transplants and have returned to typical activities with good quality of life.
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