Peripheral Blood Stem Cell Collection after Mobilization with Intensive Chemotherapy and Growth Factors*

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Abstract
Peripheral blood has become an alternative to bone marrow as a source of stem cells for transplantation. One of the major disadvantages of peripheral blood as a source is the low concentration of stem cells. For successful engraftment, the infusion of at least 6 x 108 nucleated cells per kg is required, a cell number obtained by 6-8 cell pheresis sessions. This cell number contains approximately 0.1% CD34 cells equivalent to 600,000 CD34 cells. It is known that chemotherapy and hematopoietic growth factors increase the concentration and total number of progenitor cells in the peripheral blood. In breast and lung cancer patients we are using two cytoreductive regimens: cytoxan 2 g/m2 + platinol 90 mg/m2, and VP-16 600-900 mg/m2 + platinol 90 mg/m2, respectively, in conjunction with G-CSF for stem cell mobilization. At the time of hematopoietic recovery, between day 13 and 16, the absolute number of CD34+ cells increases in 75% of the patients more than 20-fold, from 5,000 to at least 100,000/ml blood, and to more than 40-fold, to 200,000/ml, in 54% of the patients. Therefore, 3.4-7.5 ml blood contains up to 750,000 CD34+ cells, the minimum number of CD34 cells/kg body weight infused when steady-state collected peripheral blood cells are used. Since we use a minimum of 3 x 106 CD34+ cells/kg body weight, 15,000 ml of mobilized blood are required. This amount can often be obtained by collecting 500 ml blood by phlebotomy in 2-3 separate sessions, which is an easy and cost-effective method for the patient.