What is Hematopoietic Stem Cell Transplantation?

Mike Howells

Hematopoietic stem cell transplantation (HSCT) is a therapy often used in the treatment of cancer and blood diseases. The procedure involves taking healthy stem cells from a donor or patient's own blood and transplanting them into the target subject. Though a highly risky procedure, hematopoietic stem cell transplantation is still generally recommended for patients with conditions such as multiple myeloma, leukemia, and sickle-cell disease.

A diagram of the effects of leukemia.  A hematopoietic stem cell transplant is used to treat some diseases, including leukemia.
A diagram of the effects of leukemia. A hematopoietic stem cell transplant is used to treat some diseases, including leukemia.

A hematopoietic stem cell is a particular kind of stem cell that develops in blood or immune system cells. Borne from bone marrow transplants that were first developed in the late 1950s, hematopoaietic stem cell transplantation was hit upon as a way to spur new growth of blood cells in a recipient. This was first utilized to help individuals stricken with radiation poisoning, but was later recognized as being helpful for those with compromised circulatory systems as a result of blood disease.

There are several different methods for conducting hematopoietic stem cell transplantation. Autologous HSCT uses one's own cells, while allogeneic HSCT involves a separate, healthy donor. Both types have distinct benefits and drawbacks, and are employed in different situations.

Autologous hematopoietic stem cell transplantation involves first extracting an amount of a patient's own hematopoietic stem cells, introducing a high dose of chemotherapy to wipe out the cancerous cells in addition to the remaining bone marrow, and then reintroducing the original stem cells to foster new, healthy blood cell production. Advantages to the autologous method include quicker recovery of the immune system and exceptionally low chances for rejection of the reintroduced stem cells.

Though this method is generally considered the preferable one for dealing with most cases where a stem cell transplant is required, it is not universally ideal. In particular, autologous HSCT is in some ways inferior when it comes to treating acute cases of leukemia. The dangers of infection or rejection are lower, but the chances of a recurrence of cancer are increased compared to allogeneic HSCT.

Stem cells from a separate donor may be more effective at preventing a relapse of cancer, but there are generally more risks associated with it. The risk of rejection is inherently higher when from a separate donor, and even a family member's cells are far more likely to be rejected than one's own. In addition, a recipient's immune system is more greatly affected by allogeneic HSCT, as greater doses of immunosuppressants must be taken to prevent the outright rejection of the donated stem cells. This increases the chances of acquiring and possibly dying from a separate infection, such as pneumonia.

It takes roughly two weeks after hematopoietic stem cell transplantation before a patient can begin to be weened off immunosuppressants. Mortality rates from the procedure itself are above 10%, and rejection remains a threat for a minimum of six months after a transplant. The chance of an effective cure for diseases such as leukemia remains worth the risk for many patients.

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