Factors impacting stem cell mobilization failure rate and efficiency in multiple myeloma in the era of novel therapies: experience at Memorial Sloan Kettering Cancer Center

Thalidomide, lenalidomide and bortezomib have increasingly been incorporated in first-line induction therapies for multiple myeloma. Concerns regarding the impact of these agents, especially lenalidomide, on stem cell mobilization prompted us to re-evaluate the risk factors that impact mobilization, including exposure to novel induction regimens. Among 317 patients who proceeded to stem cell collection after induction therapy between 2000 and 2009, the rate of mobilization failure, defined as the inability to collect 5 × 10(6) CD34+ cells/kg following the first collection attempt, was 13%. By multivariate analysis, independent risk factors associated with mobilization failure included older age (P=0.04), lower platelet count (P=0.002) and use of single-agent G-CSF for mobilization (P<0.0001). When considering for outcome measurement stem cell collection efficiency measured by the number of CD34+ cells yielded per pheresis performed during first collection attempt, lower platelet count, use of single-agent G-CSF and older age were also associated with lower efficiency. In this population mobilized mostly with cyclophosphamide and G-CSF, the use of lenalidomide during induction was not associated with a lower stem cell collection efficiency by multivariate analysis. The data support the current International Multiple Myeloma Working Group guidelines recommending the use of cyclophosphamide and G-CSF based mobilization for patients previously exposed to lenalidomide.