Combined bone marrow and peripheral blood progenitor cell autografts for patients with poor mobilization

Background aims: Peripheral blood progenitor cell (PBPC) autografts with low CD34⁺ cell content provide inadequate platelet (Plt) and red blood cell (RBC) reconstitution. Repeat collection and bone marrow (BM) harvesting are used in this situation. Minimum cell contents for BM-PBPC combined grafts are undefined. Methods: A retrospective analysis of 19 autologous stem cell transplants (ASCT) with combined BM-PBPC for poor initial PBPC collection was carried out. Mobilization was with filgrastim (10 μg/kg/day) alone for 5 days or after chemotherapy. BM was harvested if PBPC collections were CD34⁺ 2.5>10⁶/kg. Results: The median age was 55 years (range 19-74). The diagnoses were multiple myeloma (7), non-Hodgkin's lymphoma (7), Hodgkin's disease (4) and acute myeloid leukemia (1). The median cell content (CD34⁺/kg×10⁶) was 1.1 (0.3-2.7) for BM, 1.2 (0.04-2.8) for PBPC and 2.2 (1.4-4.9) combined. Eight grafts contained > 2.0×10⁶ CD34⁺/kg (1.4-1.8). The median engraftment in days (range) was: absolute neutrophil count (ANC) ≤ 500, 12 (9-39); Plt ≤ 20 000, 25 (15-70); RBC transfusion independence, 17 (6-93). Six patients died of progressive disease (58-293 days post-ASCT), one of infection on day 141 and one of AML on day 11. All patients except one maintained ANC ≤ 1000 without filgrastim support beyond day 19. One patient had cholecystitis and delayed graft failure on day 90. PBPC CD34⁺ content did not predict CD34⁺ BM content but correlated with ANC ≤ 500 (r= - 0.64, P=0.003). BM and combined CD34+ and BM TNC/kg did not correlate with engraftment or outcomes. Combined CD34⁺/kg > or ≤ = 2.0×10⁶ produced similar engraftment and mortality. Conclusions: After a failed PBPC collection, BM harvest is a reliable option for obtaining an adequate combined autograft. Combined BM-PBPC autografts with >2.0×10⁶ CD34⁺/kg can produce satisfactory engraftment.