Mobilization with reduced cyclophosphamide for autologous stem cell transplantation is feasible in patients with systemic sclerosis

Objectives: To assess the feasibility of reduced cyclophosphamide dosing in the setting of mobilization chemotherapy prior to high dose chemotherapy and autologous stem cell transplantation in patients with SSc. The primary end point was the occurrence of 'poor mobilization' when using different cyclophosphamide dosing. The second end point was to analyse potential risk factors for difficult stem cell mobilization in this cohort of patients with SSc.

Methods: This single-centre study retrospectively reviewed 32 patients with SSc who underwent autologous stem cell transplantation. We analysed the occurrence of 'poor mobilization' (defined as CD34+ progenitor cell count <2 × 106/kg body weight, the use of increasing G-CSF dose, the use of plerixafor, or leukapheresis on >2 consecutive days) in different cyclophosphamide mobilization regimens: We herein compared low dose (2 × 1-1.5 g/m2) cyclophosphamide vs high dose (2 × 2 g/m2) for mobilization.

Results: Higher dosing of cyclophosphamide seems not to be beneficial regarding stem cell collection as there was no significant difference in stem cell yield between high dose and reduced dose cyclophosphamide (6.2 vs 5.2 × 106/kg bodyweight after CD34+ enrichment). Furthermore, higher doses of cyclophosphamide might be associated with more side effects; this difference was, however, not statistically significant. Lower bodyweight and BMI (P < 0.001) as well as rituximab pre-therapy (P < 0.05) and cardiac involvement (P < 0.01) might negatively impact stem cell collection independently from the chosen regimen.

Conclusion: Our data demonstrate that a reduced cyclophosphamide mobilization regimen seems to be feasible. Risk factors for poor mobilization might be low bodyweight, prior rituximab therapy and cardiac involvement.