Not long ago, bone marrow transplants (BMTs) were considered experimental, cutting-edge therapy. Today the procedure is mainstream, offering many cancer and leukemia patients a new chance at life. (Bone marrow transplants are also used to treat aplastic anemia and certain genetic blood and metabolic disorders.)
When it comes to killing cancer cells, high doses of chemotherapy and radiation are our most powerful weapons. The problem is, the treatments take a heavy toll on normal cells. Those include vital blood cells produced in the bone marrow—the soft, spongy material found inside bones. And some leukemia therapies actually are designed to destroy bone marrow. Yet by replacing damaged marrow, BMTs give high-dose, high-intensity chemotherapy and radiation a chance to do their work.
There are two different kinds of bone marrow transplants. In an autologous transplant, stem cells (the immature cells from which white blood cells, red blood cells and platelets develop) are extracted from the patient before the intense treatment begins. Doctors gather the cells either from a vein on an outpatient basis, a process that may go on for several weeks, or by needle aspiration from the bone marrow itself. When the marrow itself is withdrawn, it is done in the hospital under general anesthesia. The healthy stem cells are then separated from the cancerous cells and frozen until needed.
An autologous transplant is possible only if the patient’s blood cells are virtually cancer-free or if the cancer is in remission. If those conditions aren’t met, patients may benefit from an allogeneic transplant, in which the bone marrow is derived from a close family member or from an unrelated donor. In either case, the marrow must be a good match with that of the patient.
Whether the transplant is autologous or allogeneic, the healthy cells are injected into the patient’s veins only after the intense anticancer therapy has been completed. (In allogeneic transplants, the donor marrow is usually obtained and injected into the patient on the same day.) From the injection site, the good cells travel through the bloodstream to the marrow space within the bones, where they begin to produce healthy new blood cells.
The procedure takes place in a special sterile environment with excellent ventilation and filtering systems to reduce the risk of infection. Recovery is painstaking, requiring a stay of several weeks within the sterile environment.
BMT, a highly complex procedure that demands expert medical care, is not without risks and serious side effects. Primary among them is graft versus host disease (GVHD), which occurs when cells in the donated marrow (the graft) treat the recipient’s body (the host) as if it were foreign and begin attacking it. Because a BMT patient’s immune system is weak, infection, particularly pneumonia, is another potential complication. Of course, for people facing potentially lethal cancers and leukemias, those risks seem negligible. For those patients, BMT brings hope for happier, healthier days ahead.