What Is a Transplant?
Transplantation is the transfer of living tissues or organs from one part of the body to another or from one individual to another. A BMT should be thought of in terms of a transfusion rather than a surgical procedure or operation. The replacement marrow (or BPCs) is called a graft; you (the one who receives the graft) are the host.
A blood or marrow transplant can be one of two types. The type of transplant your doctor recommends depends on your age, the type of cancer or disease you have, other disease characteristics and whether a suitable related donor is available.
In an allogeneic transplant, the patient receives a replacement marrow or stem cells from another person. Sometimes, the graft launches an attack on the recipient. This is called graft versus host disease (GVHD).
In an autologous BMT, a patient is his/her own donor. The advantages of autologous BMT are elimination of the danger of GVHD and the possibility of an easier recovery period.
A blood or marrow transplant (BMT) allows doctors to aggressively treat a growing range of diseases. The transplanted blood or marrow stem cells replace diseased or damaged bone marrow. BMTs have been used to treat patients who have congenital (present at birth) and acquired disorders, as well as those who have blood-related (hematologic) and solid tumor cancers.
In patients with leukemia and aplastic anemia, the stem cells in the bone marrow do not work as they should. In leukemia, too many immature or defective blood cells are produced. They interfere with the production of normal blood cells, spill over into the bloodstream and may invade other tissues. In aplastic anemia, the bone marrow stops producing blood cells.
Strong doses of chemotherapy and/or radiation are needed to destroy these defective stem cells and the abnormal blood cells they produce. However, these therapies can also destroy normal bone marrow. Likewise, very powerful treatments, which are needed to effectively treat some soft tissue cancers (called lymphomas) and other types of solid tumor cancers, can destroy healthy bone marrow.
A BMT enables doctors to treat these diseases aggressively with chemotherapy and/or radiation, and then replace the diseased or damaged bone marrow after treatment. Although a BMT does not guarantee that the disease won’t recur, a BMT can increase the likelihood of a cure or at least prolong the period of remission in many patients.
A BMT never is taken lightly. The transplant is an attempt to cure a potentially fatal disorder. A BMT is a very difficult process and requires a great deal of commitment from both patient and family.
What Is Bone Marrow?
Bone marrow is a spongy meshwork material; it is found in the top section of your long bones, pelvic and shoulder girdles, breastbone, the ends of your ribs and the flat bones of your skull.
Blood cells are made in the bone marrow. You have several types of blood cells, each with its own special job to do. Blood cells are produced and grow in the same general way as other cells. Most tissues and organs in your body contain a supply of immature cells called stem cells. When your body needs new cells to replace worn out or damaged cells, the stem cells divide, mature and become fully developed and functional. When you no longer need them, the production of new cells slows or stops.
This process of blood cell growth and development is called hematopoiesis. Stem cells in your bone marrow contain the genetic information that controls how and which types of blood cells your body produces. Blood cells are not released from your bone marrow into your bloodstream until they are developed and ready to do the job they are supposed to do.
One special type of blood cell (called blood progenitor cells or BPCs) that circulates in your bloodstream appears to be similar to the stem cells found in your bone marrow. BPCs can repopulate damaged bone marrow and restore hematopoiesis; they can be collected from your bloodstream using a leukopheresis machine. When you read the term “blood and/or marrow transplant” in this guide, the word “blood” usually refers to BPCs, which are also sometimes called peripheral blood stem cells.