Bone marrow is a spongy tissue found inside bones. The bone marrow in the breastbone, skull, hips, ribs, and spine contains stem cells. These stem cells produce the body's blood components, including red blood cells, white blood cells, and platelets. These are the main agents of the body's immune system.
Marrow transplants are used for some patients whose marrow, because of disease, no longer produces the correct amounts of a variety of blood cells. For example, patients with leukemia may produce an excessive number of defective or immature blood cells. Patients with aplastic anemia may have low blood cell counts.
Large doses of cancer-killing drugs and/or radiation destroy the abnormal stem cells and abnormal blood cells. However, along with the abnormal cells, normal cells in the bone marrow are also destroyed. A bone marrow transplant allows physicians to treat diseases effectively with chemotherapy and radiation, and then to replace the diseased or damaged bone marrow with healthy marrow.
After the patient's diseased bone marrow is destroyed, healthy marrow is infused into the patient's blood. In a successful transplant, the new bone marrow travels to the cavities of the large bones, and begins producing normal blood cells.
Whether the patient or a donor provides the bone marrow to be used in transplant, the process — which is called the bone marrow harvest — is the same. The bone marrow harvest takes place in an operating room, usually under general anesthesia. It involves little risk and minimal discomfort. When the patient or donor is under anesthesia, the physician inserts a needle into the cavity of the rear hipbone, where a large quantity of bone marrow is located. Several skin punctures on each hip and multiple bone punctures are usually required to extract the requisite amount of bone marrow. There are no surgical incisions or stitches involved, only skin punctures where the needle was inserted.
There may be some discomfort at the harvest site. The pain can usually be controlled with acetaminophen (Tylenol).
The transplant takes place a day or two after the chemotherapy and/or radiation treatment. It is not a surgical procedure. The bone marrow is infused intravenously into the patient, in much the same way that any blood product is administered.
The two to four weeks after the transplant are critical. As the patient waits for the transplanted bone marrow to migrate to the cavities of the large bones and engraft (begin producing normal blood cells), the patient will be very susceptible to infection and excessive bleeding. This is the because the body's defense system has been disabled by the high-dose chemotherapy and/or radiation therapy that was given prior to the transplant to destroy the diseased bone marrow. Multiple antibiotics and blood transfusions are administered to the patient to help prevent and fight infection. Transfusions of platelets are given to prevent bleeding. Patients who have received a transplant from a donor (an allogeneic transplant) will be given medications to prevent and control graft-versus-host disease. This disease occurs when the patient's body recognizes the bone marrow as foreign material and tries to attack and destroy it.
Patients remain hospitalized in single room isolation. A parent may stay with the child at all times, but outside visitors are limited. The patient's exposure to viruses and bacteria is minimized. Visitors and hospital personnel wash their hands with antiseptic soap and wear protective gowns, gloves, and masks while in the patient's room. No fresh fruits, vegetables, plants, or cut flowers are allowed in the patient's room since they often carry fungi and bacteria that pose the risk of infection.
Blood samples are taken daily to determine whether or not engraftment has occurred and as a means of monitoring organ function. When the transplanted bone marrow finally engrafts and begins producing normal blood cells, the patient will gradually be taken off the antibiotics, and blood and platelet transfusions will be reduced and eventually will no longer be needed. When a sufficient number of healthy red blood cells, white blood cells, and platelets are produced, the patient will be discharged from the hospital. A patient receiving a bone marrow transplant typically spends four to eight weeks in the hospital.
The types of transplants include bone marrow, peripheral blood, and cord blood transplants using HLA-matched sibling donors, unrelated donors, and family mismatched donors.