Medical Health Encyclopedia

Donor or Patient Cells. The marrow or blood stem cells can be taken from the patient (autologous) or from a matched donor (allogeneic):

• In an autologous transplant, the marrow or blood cells used for replacement are taken from the patient. There is some danger, however, that the cells used may contain tumor cells and the cancer can regrow and cure rates are unlikely. It is unclear if this approach improves survival compared to standard chemotherapy for newly diagnosed disease. However, it clearly has benefit in the treatment of some forms of relapsed non-Hodgkin's lymphomas. There is also a higher risk for leukemia. (This risk is lower in peripheral stem cells transplants than in bone marrow transplants.)
• In an allogeneic transplant, bone marrow or stem cells are taken from a donor. Siblings are the best donors. Relapse rates can be very low with this approach and cure may be possible in some cases. However, it is highly toxic and donor and recipient must be matched as closely as possible to avoid rejection by the immune system, a serious complication called graft-versus-host disease. Advances in techniques are reducing the toxicities associated with this approach.

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The Blood Stem Cell Collection Procedure.

• The donor is usually given a drug called granulocyte colony-stimulating factor, or G-CSF (filgrastim, lenograstim, pegfilgrastim) to stimulate stem cell growth.
• The patient (or donor in an allogeneic procedure) then undergoes apheresis. With this process the blood is withdrawn from one of the patient's veins, then passes through a machine that filters out the white cells and platelets, which contain the stem cells. The blood is returned through another vein. The entire procedure takes three to four hours but needs to be repeated several times.
• The stem cells are treated to remove contaminants and then are frozen to keep them alive until the patient is ready to receive them back.

Blood is the only fluid tissue in the body. Blood transports oxygen and nutrients to body tissues, and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For instance, blood helps transport hormones from the endocrine organs to their target organs. Blood also helps maintain body temperature. The protective functions of blood include clot formation and the prevention of infection.

The Transplantation Procedure

• Allogeneic transplants are preceded by chemotherapy treatment known as conditioning. The point of this treatment is to inactivate the immune system and to kill any residual malignant cells. It is extremely toxic since it also destroys non-malignant marrow cells. Drugs used are typically cyclophosphamide, carmustine, and etoposide. Alternative conditioning to reduce toxicity includes total-body radiation plus drugs. Monoclonal antibodies, such as rituximab, are promising drugs, since they have low toxicity and may add benefits for all stages of transplantation.
• A few days after treatment, the patient given the stored stem cells, which are administered through a vein. This may take several hours. Patients may have a fever, chills, hives, shortness of breath, or a fall in blood pressure during the procedure.
• The patient may be treated with granulocyte colony-stimulating factor after chemotherapy. The goal is to stimulate the growth of infection-fighting white blood cells. Adding thrombopoietin may help enhance stem cell production.
• The patient is kept in a protected environment to minimize infection. Patients who have received an allogeneic transplant may need blood cell replacement, nutritional support, and drugs to treat graft-versus host disease. They usually can leave the hospital within 3 to 5 weeks.

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