Patients undergoing chemotherapy or radiation often require stem cell transplants to replace bone marrow that has been destroyed during cancer treatment. Stem cells live mostly in the bone marrow, where they make the three main types of blood cells: red blood cells that carry oxygen throughout the body; white blood cells that fight infection; and platelets that help blood clot. But stem cells also can be found in the bloodstream. These circulating cells are called peripheral blood stem cells.  

Collecting Peripheral Blood Stem Cells  
Because very few stem cells are found normally in the bloodstream, the collection process for peripheral blood stem cells begins with the daily injection of a growth-factor drug call filgrastim. This medicine causes bone marrow to produce and release stem cells into the blood. Side effects of filgrastim, such as bone or muscle aches, generally subside two to three days after the last dose of medication. After several days of injections, peripheral blood stem cells are collected through a process called apheresis.  

The procedure involves placing a catheter into a vein, cycling the blood through a special machine that separates and keeps the stem cells, and then returning the rest of the blood to the donor. The process takes approximately four hours and can be completed without anesthesia on an outpatient basis. Several cycles of apheresis may be necessary to collect enough stem cells. Collected peripheral stem cells are then frozen until they are given to the recipient.  

Receiving Peripheral Blood Stem Cells  
After undergoing cancer treatment, the patient receives stem cells through an intravenous line much like a blood transfusion. This process takes one to five hours. The stem cells travel to the bone marrow where they begin to grow and make new, normal blood cells. It generally takes two to four weeks for this to occur.  

Benefits of Peripheral Stem Cell Transplantation  
The collection process for peripheral blood stem cells is easier on the donor than removing bone marrow, which requires anesthesia and several needle injections.  For the recipient, his or her blood count usually recovers sooner using peripheral stem cells than with a bone marrow transplant.  

Becoming a Donor  
Peripheral blood stem cell transplantation has been used successfully for more than 20 years to treat cancer patients. You can help save lives and give hope to patients everywhere by becoming a stem cell donor. Prospective donors must meet certain health requirements and be between the ages of 18 and 60. Donors with diverse racial or ethnic backgrounds are especially needed, including African American, American Indian, Asian, Pacific Islander, Hispanic or mixed heritage. Donating is always voluntary and you can change your mind about being a donor at any time.  

For more information about bone marrow and peripheral blood stem cell transplantation, or to become a donor, go to www.giveblood.org and www.nationalmarrowdonor.com.