Stem Cell Mobilization in Poor Mobilizers Using Plerixafor and G-CSF with or without Chemotherapy: A European Perspective

Abstract 2993

High-dose chemotherapy followed by autologous stem cell transplantation is an approved therapeutic intervention in relapsed Hodgkin-lymphoma (HL) and Non-Hodgkin lymphoma (NHL). In multiple myeloma (MM) it remains standard of care in first remission. Unfortunately, a significant portion of patients fail to mobilize and collect a sufficient amount of hematopoietic stem cells, being considered as “poor-mobilizers”.

The effectiveness of the hematopoietic stem cell mobilizing agent plerixafor was evaluated in nationwide compassionate use programs in 13 European countries and reported to the European Consortium of Stem Cell Mobilization (ECOSM). Here we describe the mobilization success of 580 proven poor-mobilizers (304 male, 276 female) with NHL, HL and MM in Europe between May 2008 and August 2009. Furthermore, we analyzed the mobilization of stem cells in major NHL subgroups.

All patients received plerixafor plus granulocyte colony-stimulating factor in standard doses with or without chemotherapy. Two-hundred seventy patients with NHL (138 male, 132 female) with a median age of 56 years (range 12 – 75 years) and a median of two prior chemotherapy regimens (range 0 – 10) were enrolled. Median cell yield was 2.56 × 10 ^6 CD34+ cells/kg BW (range 0 – 17.37). The general accepted minimum of 2.0 × 10 ^6 CD34+ cells / kg bodyweight (BW) for transplantation was reached by 175 patients (64.8%) in a median of two apheresis sessions (range 1 – 4). Thirty-four patients (12.6%) yielded more than 5.0 × 10 ^6 CD34+ cells/kg BW. There were no significant differences in in stem cell harvests regarding number of prior mobilization attempts or number of prior chemotherapeutic regimens, as well as in comparing patients with diffuse large B cell lymphoma (n=28), follicular lymphoma (n=15), and mantle cell lymphoma (n=24), respectively.

Fifty-four HL patients (24 male, 30 female) with a median age of 36 years (range 19 – 76) and a median of three prior lines of therapy (range 1 – 5) were enrolled. Median cell yield was 3.14 × 10^6 CD34 cells/kg BW (range 0 – 32.6). Forty-four patients (81.5%) collected the minimum of 2.0 × 10^6 CD34+ cells/kg BW in a median of two apheresis sessions (range 1 – 4). Twelve patients (22.2%) collected more than 5.0 × 10 ^6 CD34+ cells/kg BW.

A total of 256 patients (148 male, 108 female) with a median age of 60 years (range 28 – 76) diagnosed with MM were enrolled. Patients had received a median of two prior lines of treatment and collected a median of 3.60 × 10 ^6 CD34+ cells/kg BW (range 0 – 15.27) in a median of two apheresis sessions (range 1 – 5). The minimum of 2.0 × 10 ^6 CD34+ cells/kg BW was collected by 209 patients (81.6%). Eighty-two patients (32.0%) yielded more than 5.0 × 10 ^6 CD34+ cells/kg BW allowing tandem transplantation.

Overall, the CD34+ cell yield was significantly higher in MM patients than in NHL patients (p <0.0001) and also significantly higher in HL patients than in NHL patients (p =0.013). CD34+ cell yield was not statistically significant between MM patients and HL patients. Furthermore, the number of patients collecting the minimum of 2.0 × 10 ^6 CD34+ cells/kg BW was significantly higher in MM patients compared to NHL patients (p <0.0001) and also significantly higher in HL compared to NHL patients (p =0.017). Analyzing the mobilization strategies and collection success of individual countries demonstrated only minor variations compared to the global results. Chemomobilization and steady state mobilization are used in most countries; however, there is a clear preference for chemotherapy combined with G-CSF/plerixafor in the Czech Republic, Germany, Hungary, Italy and Poland. The data emphasize the role of plerixafor in patients who failed prior mobilization attempts, but the development of improved strategies in poor mobilizers especially with NHL is required.