Mobilization and collection of PBSC in healthy donors: a retrospective analysis of the Italian Bone Marrow Transplantation Group (GITMO)

Background and objective: The number of allogeneic transplants of peripheral blood stem cells (PBSC) is rapidly increasing. Collection of PBSC in healthy subjects currently implies the administration of G-CSF or GM-CSF and, of course, the use of apheretic devices. These procedures involve potential risks, in particular the risk of leukemia secondary to growth-factor treatment. To evaluate the current practice of PBSC mobilization and collection, and initially assess the short-term side effects and efficiency of procedures, the GITMO (Gruppo Italiano Trapianti di Midollo Osseo) promoted a retrospective cooperative study among the Italian centers. Methods: Seventy-six healthy individuals donating to their HLA-identical or partially matched sibling recipients in seven Italian centers form the basis of the present analysis. The data were retrospectively collected by proper forms, pooled and analyzed by means of a commercially available statistical soft package. Results: All donors received G-CSF as mobilizing agent with different schedules according to each single center policy. A median of 2.5 (range 1-4) aphereses per donor were run. The most frequent side effect was bone pain. In no case did the medium term follow-up reveal subjective complaints or laboratory modifications. After G-CSF mobilization, WBC and lymphocytes counts increased to a maximum of (mean +/- SD) 48.1 +/- 15.6 x 10(9)/L and 4.2 +/- 1.5 x 10(9)/L, respectively. The peak was reached on day 5 in both cases. Platelets decreased after the apheretic procedures, reaching a minimum of (mean +/- SD) 77 +/- 26 x 10(9)/L on day 8 and returning to normal values on day 11. Overall, the apheretic collection yielded (mean +/- SD) 18.6 +/- 19.2 x 10(8)/kg donor body weight MNC; 10.4 +/- 5.7 x 10(6)/kg CD34+ cells; 90.6 +/- 75.9 x 10(4)/kg CFU-GM and 4.3 +/- 1.8 x 10(8)/kg CD3+ cells. The target dose of 4 x 10(6)/kg CD34+ cells was harvested in 51.3% donors after a single apheresis, in 85.5% after the second, and in nearly 100% after a maximum of 3 aphereses. Interpretation and conclusions: These data demonstrate that collection of adequate numbers of circulating progenitors is feasible and well tolerated in healthy donors. However, only careful monitoring of donors and international cooperation will help to definitively assess the long-term safety of G-CSF for mobilization of PBSC.