The goal of a bone marrow transplant is to cure many diseases and types of cancer. A BMT may be needed when the doses of chemotherapy or radiation needed to cure a cancer are so high that a person's bone marrow stem cells will be permanently damaged or destroyed by the treatment. A bone marrow transplant is also often referred to as a stem cell transplant.
What is a Stem Cell Transplant?
A stem cell transplant is a procedure which restores blood-forming stem cells in the bone marrow when they have been damaged by cancer or by cancer treatment. Blood-forming stem cells are important because they grow into different types of blood cells. The main types of blood cells are white blood cells, red blood cells, and platelets— all of which are needed in order to be healthy.
When is a Stem Cell Transplant Needed?
Stem cell transplants are used most commonly for patients with blood cancers such as leukemia, multiple myeloma, and some lymphomas. In cancers such as these, high doses of chemo (sometimes in combination with radiation), are administered with the intent of killing the stem cells. This stops the process of making new blood cells and the cells required for your immune system. Once the treatment is complete, the patient will receive a transplant of stem cells from a donor. The cells are administered through the blood and then move to the marrow where they can begin their work of regenerating the necessary blood and immune cells.
Over time, the stem cells that have settled in the bone marrow begin to grow and make blood cells that are healthy. This process is called engraftment.
Types of Stem Cell Transplants
The blood-forming stem cells that are used in transplants can be harvested from bone marrow, the bloodstream, or an umbilical cord.
There are two main types of transplants, which are named based on who gives the stem cells:
- Autologous (AUTO), where the stem cells come from you, the patient.
- Allogeneic (ALLO), where the stem cells come from someone else. Donors do not have to be a blood relative, but in many cases, a sibling will have cells that will be compatible with the patients.
If you have an identical twin, you may receive a less common type of transplant, called a syngeneic transplant. In this transplant, the stem cells are taken from your twin as long as you both have identical genetic makeup and tissue type.
The goal of an autologous stem cell transplant is to restore the body’s ability to make normal blood cells after receiving high-dose chemotherapy or radiation treatment. In this procedure, your own stem cells are harvested (removed) from your bone marrow or your blood before you get treatment that would destroy them. Once your stem cells are removed, they are frozen (cryopreservation). After you receive your chemo treatment, the stems cells are thawed and given back to you.
One major advantage of an autologous transplant is that you’re getting your own cells back. This means you aren’t at risk for graft versus host disease— a medical complication where new stem cells (called the “graft”) attack your body. However, there can still be graft failure, which means the cells don’t make blood cells as they should because they haven’t reached the bone marrow. Additionally, this type of transplant doesn’t offer the benefits of graft versus tumor (GVL) effect, which is when healthy donor cells attack cancer cells.
There are also some adverse side effects to this type of transplant, which are primarily a result of the high-intensity conditioning therapy. These effects could include:
- A higher chance of infection due to decreased white blood cells.
- The need for transfusions of red blood cells and platelets.
- Painful oral ulcers, which may make eating or drinking difficult.
- Complications, such as pneumonia, which can be a result of infection or damage from conditioning drugs used during therapy.
Autologous stem cell transplants are mainly used to treat certain leukemias, lymphomas, Hodgkin’s disease, and multiple myeloma. It is also sometimes used for testicular cancer, neuroblastoma, and certain childhood cancers.
People have different sets of proteins, called human leukocyte-associated (HLA) antigens, on the surface of their cells. The set of proteins, called the HLA type, is identified by a special blood test.
When a donor will be the source of stem cells for a cancer patient, the oncologist will aim to match the patient’s own stem cells as closely as possible. Doing this can help minimize side effects.
In most cases, the success of allogeneic transplantation depends in part on how well the HLA antigens of the donor’s stem cells match those of the recipient’s stem cells. The higher the number of matching HLA antigens, the lesser the chance the patient will reject the stem cells.
How Do Stem Cell Transplants Work Against Cancer?
Stem cell transplants help you recover your body’s own ability to produce stem cells after chemotherapy and/or radiation treatment rather than working against cancer directly.
With that said, stem cell transplants may work against cancer directly in patients with multiple myeloma and some types of leukemia. For example, a stem cell transplant where stem cells come from another person can also help treat certain types of cancer in a way other than just replacing stem cells. Cells that are donated can often find and kill cancer cells better than the immune cells of the person who had the cancer ever could. This is called the “graft-versus-tumor” (GvT) or “graft-versus-leukemia” (GVL) effect, which simply means that certain kinds of transplants actually help fight the cancer cells, rather than just providing normal blood cells.
Who is a Candidate for a Stem Cell Transplant?
Typically, stem cell transplants are used only when all other first-line treatments have failed.
Even though stem cell transplants have been successful for many people, there are risks and benefits that should be evaluated before making a decision. Your Affiliated Oncologists cancer care team should talk with you about the risks and potential benefits. They may also discuss other methods of treatment available, including clinical trials. Various factors, including your age, stage of the cancer, donor type, and overall health are all part of the decision-making process.
As with all other types of medical treatment, the final decision is yours regarding whether or not to move forward with a stem cell transplant.
Current Stem Cell Clinical Research Studies
Through stem cell therapy research, cancer stem cells (CSCs) are leading to an encouraging outlook on the future treatment of patients who have been diagnosed with germ cell tumors as well.
Germ cell tumors are growths that form from reproductive cells. They arise in the testes (in boys) and ovaries (in girls). They can also sometimes occur in other areas of the body, such as the lower back (common in infancy), the abdomen, the chest, and within the brain.
Germ cell tumors may be malignant (cancerous) or benign (noncancerous). In most cases, cancerous germ cell tumors occur as testicular cancer or ovarian cancer.
If a stem cell transplant has been recommended for you, be sure to take time to have your questions answered. If you would like a second opinion on a recommended cancer treatment plan, please contact the Affiliated Oncologists office closest to you.