Bone Marrow or Stem Cell Transplantation

Bone Marrow or Stem Cell Transplantation

Bone marrow or stem cell transplantation is an option for some people. Often, this procedure is done after an initial remission is achieved. You may want to talk to your doctor about whether this is an advisable procedure for you.

Bone marrow transplantation allows patients to receive high doses of radiation, chemotherapy, or both to eliminate cancer cells, without concern that the high dose therapy will permanently destroy their own bone marrow cells. Radiation and chemotherapy treatments (conditioning) given before transplant also destroy the immune system, which allows the successful replacement of the patient's diseased bone marrow with normal bone marrow cells that can restore normal immunity or bone marrow.

Allogeneic BMT

Allogeneic transplantation is the name given to transplants when the patient receives bone marrow, peripheral blood stem cells, or cord blood from a relative. Stem cells usually refer to circulating cells in the blood that have the same properties of cells in the bone marrow. Currently, there are three types of donors from whom bone marrow or peripheral blood stem cells can be obtained for allogeneic transplants:

• related donor - where marrow is taken from a matched or slightly mismatched sibling or other relative
• unrelated donor - where marrow is taken from a donor who is not a relative
• umbilical cord blood - where stem cells are taken from the umbilical cord and placenta of a newborn infant (This type of blood has to be closely matched to the patient.)

In order to determine if a patient has a compatible donor, testing must be performed on the blood of the patient and potential donors. This testing, which is called tissue typing or HLA typing, will tell us if the patient's body can accept the donor's bone marrow or stem cells. The selection of a suitable donor is determined by the compatibility of the donor's tissue type with that of the patient's. A group of genes make up the MHC or major histocompatibility complex in man, which produces special transplantation antigens called human leukocyte antigens (HLA). These HLA antigens are expressed on the surface of most of the body's cells. Each individual has a unique combination of HLAs on their cells, which are inherited from their parents. This combination of their antigens determines their HLA typing.

HLA Testing

When a patient begins to look for a bone marrow donor, the first step is to look at his or her brothers and sisters. There is a 25% chance that a patient will match any one of his or her siblings. In families with many siblings, this chance increases to approximately 35%. If no HLA-identical sibling donor is found or if the patient has no siblings, a decision is made based on the patient's disease, medical condition, and HLA typing to either look at extended family members (aunts, uncles, cousins, etc.) or proceed directly to a search for an unrelated donor. An unrelated donor search is performed through national and international bone marrow transplant registries which have HLA typings on thousands, and in some cases, millions of potential donors. The largest of these registries is the National Marrow Donor Program Registry which currently has close to 3 million donors. The likelihood of finding an unrelated donor for a given patient depends upon how common the patient's particular HLA type is in the general population. Certain HLA antigens occur more commonly.

The actual HLA testing is performed on a blood sample from the patient and potential donors. There are different ways that an HLA typing test can be done. These methods differ in their ability to detect differences between a patient and donor. HLA typing can be performed by "serologic typing" or by DNA molecular typing techniques. Serologic typing is often the first step in HLA typing, which identifies the major transplantation antigens that make up a patient's HLA. This test can be done rather quickly with results available within two to three days. Although serologic testing is sufficient in somet cases to identify a compatible sibling donor, more sensitive techniques using molecular typing of DNA are needed for identification of compatible "unrelated" donors. The molecular typing is very sensitive, more accurate than serology, and can detect even small differences between patients and prospective donors. In our own transplant center, all of the HLA typing is performed by DNA molecular typing. This form of HLA typing takes longer to perform with results available in approximately two to three weeks.

Bone Marrow Harvesting

Bone marrow harvesting is the procedure that removes bone marrow for later transplant. It is done in the operating room under general anesthesia. Bone marrow can be removed from multiple sites on the front and back of the hips and from the breastbone (sternum). The body replaces this marrow in two to three months. Bone marrow harvesting for autologous bone marrow transplant is done before the patient begins radiation and high-dose chemotherapy treatments. The marrow is frozen and kept until it is needed for transplant. Bone marrow harvesting from a donor for allogeneic bone marrow transplant takes place several hours before the marrow is given to the patient. Patients who will have allogeneic bone marrow transplant may also have some of their own bone marrow harvested before beginning radiation therapy and chemotherapy for back-up.

Stem Cell Harvesting

Peripheral blood stem cell harvesting is the procedure used to collect some of the stem cells in the blood. The stem cells that are removed (harvested) are frozen for later transplant.

Five days before the harvesting procedure, the donor will usually begin to have subcutaneous injections of G-CSF, a stem cell stimulating factor that helps to increase the number of stem cells in the blood. The donor or a family member will be taught how to do the injections. They are given twice a day, every 12 hours, for five days. The harvesting procedure is done once a day for two days. The donor lies in a bed or sits in a reclining chair. The process is painless and takes 3 to 4 hours. A machine that separates the stem cells from the blood will be connected to intravenous catheters in both arms. Blood is withdrawn from one catheter, circulated through the machine to collect the stem cells, and returned to the donor in the other catheter.

Very rarely, donors who have poor vascular access will have a catheter inserted that will remain in place for the two days of stem cell collection.

Most people have no side effects after the procedure is completed and can resume regular activities.