Bone marrow is the spongy tissue inside bones that produces blood cells, including white blood cells, red blood cells and platelets. Cells in the bone marrow that normally develop into the blood cells are called stem cells. When bone marrow is damaged, it no longer produces these cells. As a result, weakness, anemia, infections, excessive bleeding and even death can occur.
A bone marrow transplant (BMT), also called a stem cell transplant, is a procedure in which diseased or damaged bone marrow cells are replaced with healthy ones. This procedure is performed after a patient has high-dose chemotherapy or radiation treatment for conditions that don't respond to standard doses. When high doses of chemotherapy and radiation are used to kill cancer cells, bone marrow cells also may be destroyed. Bone marrow and stem cell transplants enable doctors to treat cancer with aggressive chemotherapy and radiation because they can replace the bone marrow cells destroyed in the treatment.
A number of blood disorders and cancers are treated with bone marrow or stem cell transplants, including:
For allogeneic transplantation, the patient receives bone marrow or blood stem cells from a donor who may or may not be a relative. Identical twin allogeneic transplants are called syngeneic transplants.
For autologous transplantation, the patient receives his or her own bone marrow or stem cells that were collected and frozen before admission for high-dose chemotherapy or radiation.
Advances in the treatment of cancer and improvements in supportive care over the past 10 years have improved the results and tolerability of bone marrow transplants. However, a bone marrow transplant remains a dangerous and difficult procedure.