Bone Marrow Transplants: The Process, Recovery

by Food and Drug Administration (FDA)

(Page 2 of 3)

The Transplant Process

"One misconception about bone marrow transplants is that the bone marrow is the only important part of this process," says Richard Jones, M.D., director of the bone marrow transplant unit at The Johns Hopkins Oncology Center. Bone marrow is certainly important, Jones says, but so is the chemotherapy or radiation treatment that precedes a transplant. "In many cases, the preparative therapy is the most important part" of the overall treatment. Therapy destroys cancer cells and defective marrow and makes room for new marrow.

This preparative regimen can be either high-dose chemotherapy or high-dose chemotherapy combined with total body irradiation, an x-ray procedure that exposes the whole body to radiation and penetrates all the body's cells. "The chemotherapy is about 10 times higher than doctors normally would give," Jones says. The anti-cancer drugs used for chemotherapy depend on the protocol of the treatment center and the type and stage of disease, but busulfan and cyclophosphamide are the most common. In February 1999, FDA approved an injectable form of busulfan. Previously used only in pill form, it's meant for use with cyclophosphamide as a conditioning procedure before allogeneic bone marrow transplants for CML.

Because side effects include severe nausea and vomiting, M. D. Anderson's Mullen says some researchers are rethinking the basic approach to transplants as it was laid out 30 years ago. "That approach was: Let's put together as toxic a drug regimen as we can and hope that the patient will survive," Mullen says. "Now some are asking whether such toxic doses are really necessary." He adds that some transplants in the adult program at the Anderson Center have been effective with lower doses of chemotherapy than were previously thought necessary. But the level needed depends on the stage and nature of the patient's disease.

Post-Transplant Recovery

After the transplant, it takes two to four weeks for engraftment — the process by which the new stem cells find their way to the bone marrow space and begin producing blood cells. Because the preparative regimen wipes out the patient's immune system, warding off infections during the recovery period is critical. Patty Clark, 41, of Baltimore, says her father served as a lymphocyte donor during her transplant. That means he gave her white blood cells to bolster her immune system, a common way to boost immunity. Her father's donated white blood cells helped protect her against infections while the new bone marrow took root and began producing its own white blood cells. Other precautions include practices such as having visitors wear a mask and gloves to protect patients from infection. Clark received an autologous transplant in spring 1999 as part of ovarian cancer treatment.

Other potential complications include organ damage from chemotherapy, bleeding problems, and two types of rejection related to the bone marrow transplant. "You're not only replacing the organ, but you're also bringing a whole new immune system with it," explains Dennis Confer, M.D., chief medical officer at the National Marrow Donor Program. One type of rejection occurs when the residual immune system of the person receiving the transplant rejects the donated marrow; a second, scarier form of rejection occurs when the donor marrow rejects the body of the patient, in what's known as Graft Versus Host Disease (GVHD). According to Confer, if the recipient rejects the marrow, blood counts will stay low. In GVHD, immune cells in the new marrow recognize the recipient as foreign and attack tissues in the body. Blood counts will come up, but the patient will experience symptoms such as a loss of appetite and energy, diarrhea, and a skin rash. If uncontrolled, GVHD will be fatal.

The immunosuppressive drug cyclosporine plays a major role in the success of an allogeneic transplant because it can help prevent GVHD and interstitial pneumonia, a lung infection caused by cytomegalovirus. "If you've had this virus and you undergo a marrow transplant, there's a high chance that it will reactivate," Confer says. Sometimes doctors also give patients growth factors, genetically engineered substances that stimulate a faster return of white cells. Examples are granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF).

As for success rates of bone marrow transplants, experts generally agree there is no clear-cut answer. These rates depend on many factors, including the type and stage of disease, the condition of the patient at the time of the transplant, the donor, and the age of the patient. Success can range from 80 to 90 percent for children with inherited abnormalities of the immune system to as low as 10 percent for patients with aggressive, resistant diseases.

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