Peripheral Blood Stem Cell Transplant (PBSCT)

Procedure, Purpose, and Complications of PBSCT's

Stem cells give rise to red blood cells, white blood cells and platelets. Credit: Getty Images

Definition: Peripheral Blood Stem Cell Transplant (PBSCT)

Peripheral blood stem cell transplants, or PBSCT's, are procedures that restore stem cells that have been destroyed by high doses of chemotherapy. Stem cells are cells that give rise to the blood cells -- red blood cells that carry oxygen, white blood cells that help the body to fight infections, and platelets that help make the blood clot.

It used to be that stem cell transplants came from donated bone marrow.

Though most of the stem cells are present in bone marrow, some are out circulating -- in the peripheral blood stream. These can be collected and then transfused in patients to restore their stem cell reserve.  Most stem cell transplants (but not all for a number of reasons) are now PBSCT's.  Prior to donating stem cells, donors are given a medication which increases the number of stem cells in the blood.  Peripheral blood stem cells work very well when compared with bone marrow transplants, and in fact, in some cases may result in platelets and a type of white blood cells known as neutrophils "taking" even better, when the donor is not related to the recipient.

Hematopoiesis - Understanding the Purpose of Stem Cell Transplants

In order to really understand how stem cell transplants work, it can help to talk a little more about what stem cells really are.  As noted above, stem cells -- also known as hematopoietic stem cells - give rise to all the different types of blood cells in the body.

  By transplanting stem cells which can subsequently differentiate and evolve into the different types of blood cells - a process called hematopoiesis - a transplant can replace a deficiency in all of the type of blood cells. 

In contrast, medical treatments to replace all of these cells are intensive and carry many complications.

  For example, you can give platelet transfusions, red blood cell transfusions, and give medications to stimulate both the formation of red blood cells and white blood cells, but this is very intensive, difficult, and has many side effects and complications. 

Reasons for a Peripheral Blood Stem Cell Transplant (PBSCT)

Chemotherapy delivered in high doses destroys cancers better, but also destroys stem cells present in the bone marrow. Stem cell transplants help restore the bone marrow so that the patient can tolerate the high doses of chemotherapy.

Types of Stem Cell Transplants

There are three types of stem cell transplant:

  • Autologous transplants: when patients receive their own stem cells.
  • Allogeneic transplants: when patients receive stem cells from their brother, sister, or parent. An unrelated donor also may be used.
  • Syngeneic transplants: when patients receive stem cells from their identical twin.

Donating Peripheral Blood Stem Cells

PBSC donation involves taking circulating blood stem cells, rather than cells from the bone marrow, so there’s no pain from accessing the bone marrow.

But in PBSC, the medication given to boost the number of stem cells in the donor’s circulation can be associated with body aches, muscle aches, headaches, and flu-like symptoms. These side effects generally stop a few days after the last dose of the stem-cell-boosting medication.

Complications of Peripheral Blood Stem Cell Transplants (PBSCT)

There are many possible complications of PBSCT's.  The high dose chemotherapy prior to the transplant poses a serious risk of infection due to a lack of white blood cells (immunosuppression) as well as problems related to a lack of red blood cells (anemia) and low platelets (thrombocytopenia.)

A common risk after transplant is that of graft versus host disease (GvH), which happens to some degree in almost all stem cell transplants.  In GvH disease the transplanted cells (from the donor) recognize the host (the recipient of the transplant) as foreign, and attack.  For this reason people are given immunosuppresive drugs following a stem cell transplant.

Yet the immunosuppressive drugs also pose risks.  The decrease in immune response due to these drugs increases the risk of serious infections, and also increases the risk of developing other cancers.

Alternatives to Traditional PBSCT

Undergoing a PBSCT is a major procedure.  Not only is it preceded by very aggressive chemotherapy, but the symptoms of graft versus host disease, and complications of immunosuppressive drugs make it a procedure that is usually reserved for younger, and in general very healthy, people.

One option that may be considered for patients who are older or in compromised health is a non-myeloablative stem cell transplant.  In this procedure, instead of ablating (essentially destroying) the bone marrow with very high dose chemotherapy, a lower dose of chemotherapy is used.  The secret behind these forms of transplants actually lies in a type of graft versus host disease.  Yet, instead of the graft - the transplanted stem cells - attacking "good" cells in the recipients body, the transplanted stem cells attack the cancerous cells in the recipients body.  This behavior is termed "graft versus tumor."

Also Known As:

PBSCT, Peripheral Blood Stem Cell Transplantation

Related Terms:

HSCT = hematopoietic stem cell transplantation

HCT = hematopoietic cell transplantation

SCT = stem cell transplant

G-CSF = Granulocyte-colony stimulating factor -- a growth factor, a stem cell boosting medication, sometimes given to donors to mobilize hematopoietic stem cells from the bone marrow into the peripheral blood.

Sources:

National Cancer Institute. Stem Cell Transplant. Updated 04/19/15. http://www.cancer.gov/about-cancer/treatment/types/stem-cell-transplant

Singh, V., Kumar, N., Kalsan, M., Saini, A., and R. Chandra. Mechanism of Induction: Induced Pluripotent Stem Cells (iPSCs). Journal of Stem Cells. 2015. 10(1):43-62.

Wu, S., Zhang, C., Zhang, X., Xu, Y., and T. Deng. Is peripheral blood or bone marrow a better source of stem cells for transplantation in cases of HLA-matched unrelated donors? A meta-analysis. Critical Reviews in Oncology and Hematology. 2015. 96(1):20-33.

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