Bone marrow transplantation is a relatively new approach to the treatment of breast cancer and is still considered experimental by many physicians. The procedure was originally developed for the treatment of patients with leukemia (cancer of the blood system), lymphoma (cancer of the lymphatic system), and other blood disorders. Very high doses of chemotherapy not only killed the cancer cells but also resulted in the death of normal cells in the bone marrow. Patients could then be "rescued" by bone marrow transplantation (that is, by implanting new bone marrow cells from a healthy person, usually a relative). While this strategy is now acceptable for the treatment of many diseases, it is still considered a high risk procedure.
Bone marrow transplantation relies on extremely high doses of drugs that may have significant and sometimes long-term side effects. Liver and kidney damage as well as lasting neurological problems may result. Short-term problems are also possible, for the bone marrow is destroyed in the procedure and the newly transplanted marrow may take time to rejuvenate. The use of new agents called colony stimulating factors, which activate the new bone marrow, have helped to reduce the time during which a patient is susceptible to infections and bleeding complications.
Other long-term side effects, such as rejection of the transplanted bone marrow cells, have been eliminated by means of autologous bone marrow transplantation. The patient's own bone marrow is collected or "harvested" from her pelvis or hipbone before she receives any chemotherapy. The harvested marrow is stored until it is needed. The patient receives very high doses of chemotherapy in the hope of killing all the cancer cells. In the process, the patient's normal bone marrow cells are also destroyed. Her own bone marrow cells can then be returned to her via injection into the vein. Surprisingly, these cells work their way back into the bone, where they begin to reseed the depleted bone marrow.
Since the patient's immune system recognizes the transplanted bone marrow as "self," rejection is not a problem.
Owing to the use of autologous bone marrow and the development of agents that help to bolster the immune system following transplantation, the dangers of bone marrow transplantation have been significantly reduced. Still, the procedure is not without risk-In general, it is reserved for patients where breast cancer has spread to distant sites, particularly when more than ten lymph nodes are involved.