Chemotherapy-Based Stem Cell Mobilization Does Not Result in Significant Paraprotein Reduction in Myeloma Patients in the Era of Novel Induction Regimens

Novel induction agents markedly improved remission rates in multiple myeloma (MM), and the continued use of chemotherapy for CD34+ stem cell mobilization (SCM) has been questioned. We examined the additional effect of chemotherapy in SCM regarding remission status/morbidity. We reviewed 236 consecutive MM patients (aged 36 to 75 years) with first autologous stem cell transplantation from January 2009 to March 2016 after chemotherapy-based SCM. Responses were measured by changes in intact Ig and free light chain levels before and after chemomobilization (International Myeloma Working Group [IMWG] criteria). Most patients (225/236, 95.3%) received novel induction regimens, which were bortezomib-based (n = 223) and/or lenalidomide-based (n = 19). Most patients (170/190, 89.5%) achieved at least partial remission postinduction and pre-SCM. Stem cells were mobilized with granulocyte colony-stimulating factor and cyclophosphamide-based (212/227, 93.4%) or etoposide-based (15/227, 6.6%) regimens. There were insignificant changes in serum Ig and free light chain levels before and after chemomobilization either in the whole cohort or subgroups. Significant improvements of the IMWG remission status were documented in only 7 of 236 patients (3.0%). Sixty-seven patients (28.4%) developed chemotherapy-related complications (neutropenic fever, sepsis, and others), resulting in 9 hospitalizations (3.8%). Our study suggests that although causing significant morbidity, chemotherapy-based mobilization fails to improve remission status. The value of incorporating additional chemotherapy for SCM is thus not evident.