Stem cell transplant. A bone marrow transplant is a medical treatment that replaces bone marrow with healthy stem cells. These replacement cells can come from either your own body or a donor.
Also known as a stem cell transplant or, more specifically, a hematopoietic stem cell transplant, this procedure can treat certain types of cancer such as leukemia, myeloma, and lymphoma, as well as other diseases affecting the immune system and blood that impact bone marrow.
What Are Stem Cells? What Is Bone Marrow?
Stem cells are unique cells capable of self-replication and differentiating into various cell types needed by the body. Scientists have found different types of stem cells in various parts of the body at different times.
According to the American Society of Clinical Oncology (ASCO), cancer and its treatments can damage hematopoietic stem cells, which are stem cells that develop into blood cells.
Bone marrow is the soft, spongy tissue inside bones containing hematopoietic stem cells. These cells are also present in the circulating blood throughout the body.
When damage occurs to hematopoietic stem cells, they cannot transform into red blood cells, white blood cells, and platelets, each of which performs critical functions:
- Red blood cells carry oxygen throughout the body and transport carbon dioxide to the lungs for exhalation.
- White blood cells are part of the immune system, combating pathogens like viruses and bacteria.
- Platelets form clots to stop bleeding.
A bone marrow/stem cell transplant involves transplanting healthy stem cells into the bone marrow or blood to restore the body’s ability to produce red blood cells, white blood cells, and platelets.
Types of Stem Cell Transplants
Autologous Transplant
In an autologous transplant, stem cells come from your own body. High-dose chemotherapy or radiation therapy used to treat cancer can damage stem cells and the immune system. Therefore, doctors extract stem cells from the blood or bone marrow before cancer treatment begins. After chemotherapy, the stem cells are returned to your body to restore the immune system and blood cell production. This process is also known as autotransplant or stem cell rescue.
Allogeneic Transplant
In an allogeneic transplant, stem cells come from a donor. After the patient receives chemotherapy or radiation therapy, doctors administer donor stem cells. Scientists call this process allotransplant.
Many patients experience a “graft-versus-cancer” effect during allotransplant, where new stem cells recognize and destroy any remaining cancer cells in the body. This is a crucial mechanism through which allotransplants treat cancer.
Finding a compatible donor is essential for an allotransplant. A compatible donor is a healthy individual whose human leukocyte antigens (HLA) match the patient’s. Siblings often make the best donors, but other relatives or unrelated volunteers can also be suitable.
If the donor’s proteins match yours, the risk of severe side effects like graft-versus-host disease (GVHD) is lower. In GVHD, the healthy transplanted cells attack your cells.
Umbilical Cord Blood Transplant
This type of transplant uses stem cells from umbilical cord blood, which connects a fetus to the mother before birth and is not needed by the baby post-birth. Cancer centers globally use cord blood for transplants.
Haploidentical and Non-HLA-Matched Transplants
Cells from a parent, child, or sibling are not always a perfect HLA match but have 50% compatibility. Doctors increasingly use these transplants to broaden the scope of effective cancer treatments.
Finally, to learn more about Stem Cells, read our article What Are Stem Cells?
