Bone Marrow Transplants and Stem Cell Transplants for Cancer Treatment
Where Do Transplanted Stem Cells Come From? continued...
Autologous transplants involve stem cells taken from your body before you’ve received chemotherapy and radiation. The stem cells are frozen, then reintroduced to your body after treatment.
Allogenic transplants involve stem cells that come from another person whose stem cells "match" yours. Most donors are relatives -- preferably and most often a sibling.
To find out if stem cells match, a potential stem cell donor will have his or her blood tested in a process called human leukocyte antigen testing (HLA testing). In those very rare cases where the donor is your identical twin -- and thus a perfect match -- it’s called a “syngeneic transplant.”
Another source of donated stem cells is blood taken from the umbilical cord and placenta after childbirth. Some people choose to store or donate this blood after having a baby instead of discarding it. The process of taking the blood doesn’t pose a risk to the mother or child. However, because only a small amount of blood is in the umbilical cord and placenta, cord blood transplants are generally only used in children or small adults.
Stem cells can also come from what is known as a matched unrelated donor. Your bone marrow and blood typing is matched against an unknown donor via a bone marrow registry to find a compatible donor. Doctors will search bone marrow registries if the patient does not have a relative who “matches” their stem cells.
Collecting Bone Marrow or Stem Cells for Cancer Treatment
How would a doctor collect stem cells from you or a donor? That depends on whether you’re getting a peripheral blood stem cell transplant or a bone marrow transplant for cancer treatment.
- Peripheral blood stem cells. In this approach, the stem cells circulating in the donor’s blood are harvested and stored. This technique has become more common than bone marrow transplants for cancer treatment. Peripheral blood stem cell transplants are as effective for some, but not all cancers, but the process of donating is simpler.
For a few days, the donor -- whether it’s you or another person -- will take special drugs that temporarily increase the number of stem cells in the blood. Side effects of this drug include bone pain. Then, a health care professional would insert a catheter into a vein to filter the donor’s blood through a special machine. This device extracts the stem cells and circulates the blood back to the body.
The process usually takes two to four hours. The donor might need to repeat the process for a few days before enough stem cells have been collected. The stem cells are then frozen until the transplant. The risks are very low. Side effects during the procedure include faintness and cramps in the hands.
- Bone marrow stem cells. Because harvesting bone marrow is more involved, it’s done in an operating room. The donor will be under either general anesthesia (and asleep) or regional anesthesia (which eliminates feeling from the waist down.) A doctor will then insert a needle into a bone -- usually in the hip -- and withdraw some of the bone marrow, which is then stored and frozen.
The process takes one to two hours and the risks are very low. The most serious danger comes from the anesthesia itself. The area where the needle is inserted might be sore or bruised for a few days. Donors might also feel tired for several days or weeks afterward.