Short and Long Term Efficacy of Autologous Bone Marrow Cells To Support Intensive Chemotherapy in Patients Failing Peripheral Blood Stem Cell Mobilization.

Introduction: Most autologous hematopoietic cell transplants (AHCT) are performed using peripheral blood mobilized progenitor cells (PBSC). However a small but significant proportion of patients (pts) are unable to mobilize adequate numbers of PBSC. The use of G-CSF-stimulated bone marrow (BM) derived progenitor cells is one method to circumvent this problem and enable AHCT to be performed. However, the long and short-term ability to engraft and the impact of this method on overall and progression free survival (OS and PFS) have not been established.

Methods: We reviewed 52 pts (17 AML, 24 NHL, 11 HL) who failed PBSC collection between Jan 1999-Dec 2006 (<2×510⁶ CD34+cells/kg) and underwent G-CSF stimulated BM harvest to permit high dose therapy (etoposide 60 mg/kg + melphalan 160–180 mg/m², + TBI 500 or 1200 cGy for pts with AML). 23 pts were supported by harvested BM (44%) and 29 (56%) with a mixture (Mx) of BM and PBSC. Overall and PFS was compared to pts undergoing AHCT using chemotherapy-mobilized PBSCs (n=440) in the same time period (AML n=32, NHL n=273, HL=135) who had a similar median age, pre-transplant induction, salvage therapy and intensive therapy regimens. Kaplan-Meier curves and the Log-rank test were used to compare the OS and PFS between cases and controls. Due to skewed data, the non-parametric Wilcoxon Rank Test was used for simple comparisons of clinical factors.

Results: Median age of the cohort at AHCT was 43 years (range 24–68, 67% females). Status prior to AHCT was CR 44%, PR 54%, and SD 2%. Number of chemotherapy regimens (median):AML: 3; NHL: 3; HL: 2. Median BM CFU-GM infused was 4.4×10⁴/kg and median PBSC infused was 0.1×10⁶/kg (n=29). Median follow up times for AML/NHL/HL was 20, 18 and 50 months respectively. Twenty-three pts died:18 from disease progression, 4 treatment-related (TRM) and one of second cancer. Median engraftment time for neutrophils (>0.5×10⁹/L) was 14 days and platelets (>20×10⁹/L) was 27 days and was significantly longer compared to pts who received PBSC alone (10 and 11 days, respectively, p<0.0001). Pts receiving Mx grafts had significantly faster engraftment vs those receiving BM alone (p<0.001). Transfusion requirements (median) during the ASCT admission were 4 units for RBC and 25 units for platelets. Median 12 month Hb, platelet and neutrophil counts were 116 g/L (70–149), 113×10⁹/L (21–238) and 2.4×10⁹/L (0.3–6.2). Two year OS of patients who received harvested BM versus PBSC alone was: 63%/71% (AML, p=0.51), 57%/70% (NHL, p=0.04) and 71%/94% (HL, p=0.04). There was no significant difference in PFS between BM recipients and controls. Non relapse mortality was 5/52 (9.6%) for pts receiving BM compared to 18/440 (4%) supported by PBSCs.

Conclusion: Performing an AHCT with BM in patients failing PBSC collection is feasible. Although engraftment is significantly delayed it appears sustained at 12 months post AHCT. Overall survival is inferior compared with patients receiving PBSC alone. Reasons for inferior disease-specific outcomes for pts with lymphoma receiving BM need to be determined.