MINIMAL NUMBER OF CIRCULATING CD34-BLOOD PROGENITOR-CELL TRANSPLANTATION( CELLS TO ENSURE SUCCESSFUL LEUKAPHERESIS AND ENGRAFTMENT IN AUTOLOGOUS PERIPHERAL)

BACKGROUND: The number of peripheral blood (PB) CD34+ cells has been w idely used to monitor the timing of leukapheresis for autologous trans plantation. However, no cutoff value for CD34+ cells in PB has been de fined as a guideline for the identification of patients in whom the ha rvest would be effective and those in whom there was a high probabilit y of failure. STUDY DESIGN AND METHODS: The present study investigated the best threshold of CD34+ cells in PB for successful harvesting and engraftment, using 263 PB samples with their corresponding leukaphere sis components. In addition, that measure has been compared to other c ommonly used criteria such as the white cell count, the number of mono nuclear cells, and the number of colony-forming units-granulocyte macr ophage in PB. RESULTS: Time to engraftment of both granulocytes and pl atelets was significantly influenced by the number of CD34+ cells tran sfused, but all patients receiving greater than or equal to 0.75 x 10( 6) CD34+ cells per kg achieved engraftment within a reasonable number of days (>0.5 x 10(9)/L granulocytes by Day II and 220 x 10(9)/L plate lets by Day 13). A clear correlation between the number of CD34+ cells per mu L in PB and of CD34+ cells per kg collected was found at each apheresis (r = 0.9, p<0.0001). Moreover, the number of CD34+ cells per mu L measured in PB the day the first leukapheresis was initiated dis played an excellent correlation with the total amount of CD34+ cells p er kg finally collected (r = 0.81, p<0.0001). On the basis of the regr ession curve obtained and the clinical engraftment results, it was fou nd that the presence of >5 CD34+ cells per mu L in PB ensured a good y ield from the harvest in 95 percent of patients and would avoid an uns uccessful harvest in 81 percent of cases. CONCLUSION: A dose of only 0 .75 x 10(6) CD34+ cells per kg guarantees hematopoietic recovery withi n a reasonable number of days. To initiate a leukapheresis from which enough progenitor cells may confidently be obtained, a minimum of 5 CD 34+ cells per mu L in PB is required.