Autologous Stem Cell Transplant
A Stem Cell Transplant (SCT) is a way of using someone's own stem cells instead of someone else’s bone marrow. For autologous (pronounced au-tol'-o-gous) transplantation, the patient receives his or her own bone marrow or stem cells that were collected and frozen before receiving very high-dose chemotherapy or radiation. The process usually takes about 3 months.
There is no donor needed for the procedure because in an autologous transplant the patient is both the donor and the recipient of the bone marrow. Patients undergoing autologous transplantation are at lower risk of infection than are those receiving allogeneic (donor) transplants. An autologous BMT is possible if the disease afflicting the bone marrow is in remission or if the condition being treated does not involve the bone marrow. The bone marrow is extracted from the patient prior to transplant and may be "purged" to remove lingering malignant cells (if the disease has afflicted the bone marrow). Stem cells are the immature cells in blood that go on to form white and red blood cells, as well as platelets.
The main purpose of a stem cell or bone marrow transplant in cancer treatment is to make it possible for patients to receive very high doses of chemotherapy and, in some cases, high doses of radiation therapy as well.
There are generally four steps in autologous transplants:
The first step in the process of preparing for a SCT is the induction treatment. The induction chemo also referred to as salvage chemotherapy is done to establish whether the patient's cancer is responsive to treatment or not and because the cancer must be put into remission (usually by chemotherapy) before the stem cell harvesting can be done. Once the cancer is in remission, the stem cells may be harvested. In the bone marrow, there is approximately 1 stem cell in every 100,000 blood cells. The bone marrow in the breast bone, skull, hips, ribs, and spine contains the stem cells. In the blood stream, the number of stem cells is about 1/100 of that in the bone marrow.
Collection of the Stem Cells
Transplantation of the stem cells from the blood stream is sometimes used in addition to, or instead of, traditional bone marrow transplantation. The collection of stem cells from the marrow is a surgical procedure in a hospital operating room, usually under general anesthesia. It involves little risk and minimal discomfort. While the patient is under anesthesia, a needle is inserted into the cavity of the rear hip bone called the iliac crest, where a large quantity of bone marrow is located. The bone marrow is a thick, red liquid which is extracted with a needle and syringe. There are no surgical incisions or stitches involved. The needle that collects the marrow is inserted by pucturing the skin. Several skin punctures on each hip and multiple bone punctures are usually required to extract the bone marrow.
Peripheral stem cells can sometimes be harvested in a process called apheresis or leukapheresis. In this procedure, blood is removed from the patient through an intravenous catheter or through a large vein in the arm and is run through a machine that collects stem cells which returns the rest of the blood to the patient. Usually, apheresis takes 2 to 4 hours and is repeated an average of six times. Once collected, the stem cells are then frozen and stored for later transplantation
High Dose Chemo
After the harvesting of the stem cells, the patient must then undergo very high dose treatments to kill any disease that might be left in the body. This chemo is so strong that it also destroys the bone marrow, which is why the transplant is needed. High dose chemotherapy (HDC) is a lethal dose of chemotherapy, enough chemo to kill off virtually all existing blood cells and the blood cell producing cells in the marrow. Needless to say, this would normally cure the disease, but kill the patient.
After the treatment, the patient is no longer able to produce blood cells. Destroying the marrow may be a part of treatment for a disease that has affected the bone marrow or it may be a side effect of treatment. In either case the patient needs a “jump start” to get their bone marrow back to producing blood cells, so the stem cells are put back into the body by way of a catheter or port implanted in the patient’s body, which places the cells into the blood stream, rather like a blood transfusion. The stem cells travel to the bones from the blood stream to stimulate production of new bone marrow that migrates to the cavities of the large bones, engrafts and begins its job of producing normal blood cells, new WBC's (white blood cells), RBC's (red blood cells), and platelets. Blood cell production from the transplanted stem cells usually occurs within about 2 to 4 weeks following the transplantation procedure. A complete recovery of immune function takes up to several months for autologous SCT patients.