High-dose chemotherapy (HDC) and bone marrow or blood stem cell transplantation (SCT) are the best treatments available for many kinds of cancer. To deliver high-dose chemotherapy, stem cells must be collected before treatment for infusion into the patient to support the recovery of the patient’s bone marrow.
The SCT procedure was developed more than 35 years ago and was considered such a major development of biomedical science that the individuals responsible were awarded the Nobel Prize in Medicine in 1989. Continued refinement has made SCT safer and widely available. In order to determine the role of HDC and SCT for the treatment of cancer, it is important to understand the terminology associated with this increasingly utilized treatment strategy.
Chemotherapy drugs and radiation therapy are used to treat cancer. Higher doses of therapy kill more cancer cells than lower doses of therapy in certain types of cancer. When higher doses of therapy kill more cancer than lower doses, doctors say there is a “dose response effect.” The delivery of higher doses of therapy is referred to as dose-intensive or high-dose therapy. Unfortunately, the higher doses of therapy used to destroy cancer cells also cause damage to normal cells. The body’s normal cells that are most sensitive to destruction by high-dose therapy are the blood-producing stem cells in the bone marrow.
Stem cells are early blood-forming cells that grow and mature in the bone marrow, but can circulate in the blood. When high-dose therapy is used to treat cancer, one of the major side effects is destruction of the stem cells living in the bone marrow. It is important to collect stem cells prior to treatment with high-dose chemotherapy so that the stem cells can then be infused to “rescue” bone marrow and hasten blood cell production and immune system recovery.
Stem cell transplants are classified based on which individual donates the stem cells and from where the stem cells are collected. Stem cells may be collected from the bone marrow, peripheral blood or umbilical cord. Therefore, the terms bone marrow transplantation, peripheral blood stem cell transplantation and umbilical cord transplantation are utilized. There are important advantages and disadvantages to utilizing stem cells collected from these different sources. The second part of stem cell transplant classification is determined by who donates the stem cells. Stem cells may come from the patient (autologous), an identical twin (syngeneic) or someone other than the patient (allogeneic). Allogeneic stem cells are further classified by whether the individual donating the stem cells is related or unrelated to the patient.