Hematopoietic stem cell transplantation is performed to treat advanced neuroblastoma. A neuroblastoma is a solid tumor. Then, why should the bone marrow be replaced? Autologous transplantation is generally used for neuroblastoma (the bone marrow or peripheral blood stem cells are removed from a patient in advance, and they are returned to the patient's body after high-dose chemotherapy or radiation therapy). The primary objective is to eradicate the tumor cells with an unusually high dose of anticancer drugs or radiation. After such intensive therapy, hematopoietic cells in the bone marrow are depleted, and the bone marrow loses its normal hematopoietic function. The stem cells that have been stored in advance are returned (transplanted) to recover hematopoietic function. Therefore, accurately speaking, autologous transplantation does not mean replacing of the bone marrow, but temporarily evacuating the hematopoietic cells outside the body and then returning them back into the body after intensive therapy. Some people may think of bone marrow transplantation as a surgical procedure replacing bones containing the bone marrow, but in fact, it is more like a blood transfusion. A liquid containing stem cells are infused into the vein. Generally, the patient spends 2 to 4 weeks in a clean room until the recovery of the hematopoietic function.
What is hematopoietic stem cell transplantation?
After bone marrow has been depleted due to high-dose anticancer drugs or radiation, hematopoietic stem cells are transplanted into the bone marrow. Figuratively speaking, stem cells are like seeds of the blood. They grow into red blood cells, white blood cells, and platelets (through a series of transformations), and the normal hematopoietic process is reconstructed. This is like using herbicides (anticancer drugs) and plowing with a bulldozer (radiation), and then planting seeds (stem cells) in the field (bone marrow). If a beautiful field of flowers (normal hematopoietic function) appears, the field work has been successful (successful engraftment). However, the seeds may not grow successfully if the field (bone marrow) is damaged by the previous treatment. This is called rejection. In case of a disease of bone marrow (e.g., leukemia), weeds (malignant cells) may begin to grow again in the field (i.e., recurrence). There are different types of hematopoietic stem cell transplantation depending on the type of stem cell: bone marrow transplantation, peripheral blood stem cell transplantation, and cord blood transplantation.