Bone Marrow Transplant
Bone marrow is a spongy substance found inside our large bones, such as the femur (thigh), hip, and ribs. It is made up of cells called hematopoietic stem cells. It is these cells that are given (transplanted) to the patient during a stem cell transplant. (NOTE: These stem cells are different than those we have heard about lately in the news; those are called embryonic stem cells.) Hematopoietic stem cells are "baby" cells that grow up to become either white blood cells, red blood cells and platelets. The bone marrow acts as a greenhouse for these cells, growing them and storing them until they are needed. What do we need them for?
- White blood cells (also called leukocytes) are the body's infection fighting cells.
- Red blood cells (also called erythrocytes) carry oxygen from the lungs to the rest of the body and return carbon dioxide to the lungs as waste.
- Platelets (also called thrombocytes) help the body form blood clots to control bleeding.
What does autologous mean?
Autologous means structures or cells derived from you and your body. For example, if our patient Jack is to have a stem cell transplant, we will get those stem cells from Jack himself. Many people think a transplant has to be something taken from a donor, but that would be called an allogeneic transplant (which is discussed in a separate article). In an autologous transplant, Jack the patient "donates" his cells to himself.
What types of cancer is this therapy used for?
Autologous transplants are used to treat leukemias, myelodysplastic syndrome, multiple myeloma, Hodgkin's disease, non-Hodgkin's lymphoma, testicular cancer and neuroblastoma.
How cells are collected.
When doctors first started doing these procedures, the only way to get stem cells was directly from the bone marrow. The patient would be taken to the operating room and put to sleep lying on his/her stomach. The doctors would put long needles into the hip bones and pull out the bone marrow in syringes. The solution was then poured through a special column that pulled out only the stem cells, allowing any other cells (mature red and white blood cells and platelets) to be reinfused into the patient. In order to get the number of cells needed, the needles would need to be inserted many times. These cells were then frozen in a special preservative (called Dimethyl sulfoxide or DMSO) to protect them from "freezer burn" until they were used.
Doctors soon found that giving the patient a medication called granulocyte colony stimulating factor, or GCSF, would stimulate the stem cells to be released from the bone marrow and into the blood stream. Using a blood test, doctors could tell how many cells were circulating in the blood stream. Once the number was high enough, the patient would go to the pheresis department at the hospital to have the cells removed.
The cells could be removed using either a catheter in the chest wall or 2 large intravenous (IV) catheters, one placed in each arm. Blood would be taken out of the patient, be circulated through the pheresis machine to remove the stem cells, and then the rest of the blood would be returned to the patient. The cells would be frozen in the same DMSO preservative as the bone marrow. During the collection, the patient may experience tingling or numbness around their lips. This is caused by a loss of calcium and can usually be resolved by eating some calcium tablets.
After infusing the stem cells, where do they go?
The cells are quite smart, and they find their way back to the bone marrow space and get to work. Remember, when the stem cells arrive in the bone marrow, things are in bad shape - almost all of the old marrow cells have been killed (ablated) by the chemo. The stem cells get right to work and produce new white and red blood cells and platelets. It can take anywhere from 7 to 14 days for the stem cells to produce new cells, and for those new cells to mature enough to function.
What is engraftment?
Engraftment is a term the doctors use to describe the point when the stem cells start doing their job and blood cell counts start to come up. The first number we look for is the neutrophil count, which is the type of white blood cell that is most important in fighting infection. Generally, once the neutrophil count gets above 500, the patient can come off antibiotics, and in many cases can go home. The time until engraftment varies from patient to patient, but is usually between 7-12 days. The red blood cell and platelet counts can take several weeks to get back to a normal range, but the patient can usually go home once they are not regularly requiring blood or platelet transfusions.
How will the person feel once he or she is home?
This can vary greatly from person to person, depending on what has happened over the past few weeks. It can take people weeks, months, or even a year to feel like their "old self" again. Some patients report having no appetite, or food tasting like metal, for months after the transplant. This can be a difficult time, as family and friends may assume that the person is "better" since they are home and the transplant is over. They may expect the person to be back at work, to return to school, or to run a household. The patient should resume normal activities slowly and add on jobs or duties every couple of days.
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