Monitoring of CD34(+) cells during leukapheresis allows a single, successful collection of hemopoietic progenitors in patients with low numbers of circulating stem cells

We have studied a total of 188 patients with hematological malignancies, su bmitted to mobilization therapy with G-CSF associated or not with chemother apy in order to: (1) establish the lower limit of circulating progenitor ce lls that allows the collection of 2 x 10(6) CD34(+) cells/kg by a single le ukapheresis, utilizing the instrument set on standard parameters; (2) evalu ate whether the number and quality of CD34(+) cells collected remain stable during leukapheresis; and (3) collect a sufficient number of circulating C D34(+) cells by a single procedure in patients in whom such an approach wou ld have been insufficient to reach the target with the instrument set on st andard parameters. The retrospective analysis conducted in 85 patients show ed that 19 circulating CD34(+) cells/mu l represented the cut-off number ca pable of discriminating between patients who will require one or more apher esis to collect 2x10(6) CD34(+) cells/kg. The validity of this value was pr ospectively confirmed in 70 subsequent patients. Based on in vitro results that showed the stability in the number of CD34(+) cells, the proportion of different CD34(+) cell subpopulations and the clonogenic capacity of the s tem cell compartment during leukapheresis both in the blood of the patients and in samples taken directly from the instrument, we have adapted the blo od volume to be processed in 33 patients with <19 PB CD34(+) cells/mu l. St em cell collection was monitored during the leukapheresis and the procedure was prolonged for a time period estimated to be sufficient to reach the ta rget number of CD34(+) cells with a single procedure. The median increment of the total blood volume processed, calculated from the volume set automat ically by the instrument was 25.2%, with a median of 3.3-fold total blood v olume processed. In all cases, a sufficient CD34(+) cell collection was com pleted in a single procedure, After autograft, the pattern of blood reconst itution was similar to that of all the other patients.