Stem cell transplantation: The basics
Advances in treatment for blood cancers
In recent years, substantial strides have been made in the research, treatment and prevention of blood diseases. Patients now have access to new, targeted therapies, aggressive chemotherapy regimens, advanced radiation therapies and improved integrative oncology services.
A stem cell transplant (or hematopoietic progenitor cell transplantation) is a promising option for some hematologic cancer patients. Advances in stem cell research have refined traditional approaches to reduce complications and provide better benefits for patients.
How does blood cancer develop?
Blood cancers originate from hematopoietic (blood) stem cells. Stem cells are immature cells that can develop into any of the three main types of blood cells. The main function of blood cells is to fight infections, carry oxygen and other important nutrients, and guard against abnormal bleeding.
When blood cancer develops, a cell in the bone marrow (e.g., leukemia, multiple myeloma) or lymphatic system (e.g., non-Hodgkin, Hodgkin lymphomas) undergoes a change and begins to reproduce uncontrollably, crowding out healthy cells over time.
Types of stem cell transplants
A stem cell transplant infuses more healthy blood-forming cells into the body to stimulate new bone marrow growth, suppress the disease and restore the immune system. Stem cells can be found in the bone marrow, circulating (peripheral) blood and umbilical cord blood.
There are two main types of stem cell transplants:
Autologous stem cell transplant
In this type of transplant, stem cells are collected from the patient themselves. The stem cells are removed from the patient’s blood, harvested, frozen and stored, and then given back to the patient after intensive therapies.
Some patients may be eligible for two autologous transplants (also called a tandem transplant). In a tandem transplant, the patient undergoes a second transplant within six to 12 months after the first one.
Allogeneic stem cell transplant
In this type of transplant, stem cells are taken from a matching donor. The patient undergoes a human leukocyte antigens (HLA) test to determine if a donor’s stem cells are the right match. The test compares the patient’s blood and tissue type against blood samples from the donor.
Donors may include:
- HLA-matched relative (most often a sibling)
- HLA-matched unrelated donor
- HLA miss-matched family member
- Unrelated umbilical cord blood
An advantage of an allogeneic transplant is that the stem cells come from a healthy donor with no malignant cells. However, since it can be difficult to find a matching donor, an autologous transplant is usually more common.
The stem cell transplant process
Before a stem cell transplant, you will likely undergo a conditioning regimen, which involves intensive treatment to destroy as many cancer cells as possible. You may receive high doses of chemotherapy and, in some cases, radiation therapy (e.g., Total Body Irradiation). Some patients may receive reduced-intensity conditioning (a “mini-transplant”), which uses lower, less toxic doses of chemotherapy.
Once this preparative regimen is complete, you are ready to undergo the transplant. Much like a blood transfusion, you’ll receive the stem cells intravenously. The procedure takes about one to five hours.
After entering the bloodstream, the stem cells travel to the bone marrow and start to make new blood cells in a process known as engraftment. The transplant restores the supply of normal cells that have been destroyed by the intensive therapies.
In the months following the transplant, your doctors will monitor your blood counts on a frequent basis. You may need transfusions of red blood cells and platelets.
Sometimes, the intensive treatments you receive before the stem cell transplant can cause side effects, such as infection. One risk of an allogeneic stem cell transplant is graft-versus-host-disease (GVHD), a condition where the donated cells attack the patient's tissues. Your doctor may prescribe certain drugs to reduce the risk of infection or GVHD.
Cord blood transplants
A cord blood transplant is a promising option for some patients without a closely matched donor. Umbilical cord blood (which has traditionally been discarded after a baby is born) is rich in blood-forming stem cells. Studies have found that cord blood transplants may help to reduce the risk of GVHD, since the transplanted stem cells are unspecialized and have not yet developed features that can be recognized and attacked by the immune system.