Transplants involving peripheral blood stem cells (PBSC) are the most common type of transplant in the sphere of cancer treatment. They fall under the wider class of hematopoietic stem cell transplants (HSCT), which includes bone marrow transplants. The term 'peripheral' may be confusing to some, but it merely means 'circulating'; in other words, in PBSCs, the source of the stem cells is circulating blood, as opposed to bone marrow.
All hematopoietic stem cell transplants are categorized by the donor source:
- In an autologous transplant, the recipient is also the donor.
- In an allogenic transplant, the recipient receives stem cells from a donor who is determined to be a good match by what is known as a human leukocyte-associated (HLA) type blood test
A third category, syngeneic transplants, is very uncommon; in this case, patients receive marrow from an identical twin.
What it's effective for and why
Peripheral blood stem cell transplants are effective and often curative second- or third-line treatments for patients suffering from a host of blood disorders including most forms of chronic and acute leukemia, several subtypes of both Hodgkin's and non-Hodgkin's lymphoma, and to a lesser degree, neuroblastoma and multiple myeloma. In any stem cell transplant, the patient's own reservoir of stem cells is destroyed through high-dose chemotherapy and radiation, making way for the healthy donor cells to be introduced into the body so that they can begin to generate the three types of cells necessary for normal function: red cells (for oxygen transportation), white cells (for immune system function) and platelets (to clot the blood and stop bleeding).
Risks and Complications: Overview
Transplantation of any organ or tissue from one person to another inherently brings with it certain complications. In solid organ transplants, one concern is graft rejection, in which the recipient's immune system rejects the donated organ or tissue. In PBSC transplants, the opposite holds true: when receiving cells from a donor, the concern is that the stem cells will reject the recipient by attacking existing cells in the body as foreign antigens. This is known as Graft-Versus-Host Disease (GVHD). Drugs are used to help prevent this potentially lethal complication.
Another potential complication arises from the need to suppress the patient's immune system so that it cannot reject the transplant; doing so leaves the patient vulnerable to any number of infections, which is why the patient must spend considerable time in a highly sterile environment.
Finally, the patient's exposure to pre-transplantation high-dose chemotherapy and radiation makes possible the many complications and side effects associated with these anti-cancer treatments. In the long term, the patient is also at risk of developing secondary cancers from these treatments.
Be The Match
Peripheral blood stem cell transplants can only treat a cancer patient if the right match is found. If you are interested in becoming a PBSC donor in the United States, get more information from the National Marrow Donor Program at www.marrow.org.
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