Depletion of tumor cells from first leukapheresis. Tumor contamination was determined in the PBPC product before and after CD34 selection. The number of tumor cells was calculated as the product of the total number of nucleated cells and the percentage of tumor cells detected. The figure represents the log number of tumor cells detected in the 24 of 28 patients (86%) in the CD34-selected arm with detectable tumor cells in the first leukapheresis. For those products purged below the detection level of the assay, the line intersects 0 on the x-axis (no detectable tumor cells). Only 2 of the 24 patients had their autografts purged of tumor cells by less than 2 logs (dashed lines).