Tuesday, November 15, 2005

Stem Cells in Cancer Treatment

by Sharon Ron (Class of '05)

Chemotherapy, as a treatment for high-risk cancers, is most commonly coupled with a bone-marrow transplant. However, provocative new evidence shows that patients that undergo peripheral blood stem-cell transplantation opposed to bone-marrow transplantation experience fewer complications, speedier recoveries and have improved relapse and survival rates.

The treatment of chemotherapy kills off cancer cells, however in the process it also kills of hematopoietic stem-cells. These stem cells are essentially immature blood cells produced in the bone marrow and can develop either into red blood cells, white blood cells or platelets. These cells are essential to life so when they are killed off in large amounts during chemotherapy the patient is put at risk for life-threatening infections. This is why procedures such as stem-cell transplantation are vital.

While it is true that all that is needed for a patient is some sort of stem-cell transfusion, research is finding that the stem-cells in bone-marrow are not as effective in stowing off disease as those from peripheral blood. In a study done on small cell lung cancer (SCLC), 18 patients were treated by means of chemoradiotherapy and then received two cycles of treatment with chemotherapy drugs followed by an infusion of peripheral blood stem cells collected from the bloodstream. The typical symptoms seen after chemotherapy, such as higher toxicities, diarrhea and kidney problems arose infrequently. Another study led by Clinical Research Division found that out of 172 patients evaluated, the survival rate for cancer patients transplanted with stem-cells was 65% while the rate of survival for bone-marrow transplantation was 45%. “The results are exciting because most strategies aimed at reducing relapse are associated … with more complications and higher mortality,” says the scientist leading the study, Dr. William Bensinger. He suggests that the difference may lay in functional differences between marrow stem-cells and stem cells from peripheral blood. Bensinger speculates that stems-cells are more abundant in peripheral blood than in bone marrow, although not enough sufficient research has been done to prove this.

The stem-cell collection process might prove to be key in discovering what accounts for this substantial difference. Stem-cells from bone-marrow are removed via a large syringe, injected into the donor’s hip bone until the correct amount or marrow has been collected. However, the process of collection from peripheral blood is to stimulate stem-cell growth through drug injections and then after a few days to collect the blood. The process used separates and collects only the white blood cells because these cells contain all the stem-cells of the blood. Therefore, patients undergoing a transplant of peripheral blood stem-cells also receive a large amount of t-cells.

The patients treated with stem-cells from peripheral blood rather than bone-marrow are clinically proven to have quicker recoveries and less relapses, complications, and deaths. With evidence such as this it seems a change in the chemotherapy recovery process is imminent.

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