Plerixafor can rescue the outcome of failing chemotherapy-based stem cell mobilization. However, the optimal time for plerixafor injection in this setting has not been determined. This was investigated by retrospective analysis of data from 48 mobilizations with plerixafor, chemotherapy, and granulocyte-colony stimulating factor (G-CSF). The required yield of 2.0 × 10(6) CD34+ cells/kg was collected from 71% of patients; the median total yield was 4.1 × 10(6) CD34+ cells/kg. Patients to whom plerixafor was administered late (≥ 15 days) after chemotherapy, after a long duration (≥ 13 days) of treatment with G-CSF, or when the white blood cell count was high (≥ 20 × 10(9)/L) were mobilized as efficiently as other patients. Plerixafor was shown to rescue mobilizations at a comparable rate in patients with critically low levels of peripheral blood CD34+ cells (<3/µL) and those with higher concentrations. These data suggest that late administration of plerixafor in the course of chemotherapy-based mobilization does not contribute to the failure of this strategy.

Multiple myeloma (MM) is an incurable plasma cell malignancy, which is predominantly a disease of older adults (the median age at diagnosis is 70 years). The slow progression from asymptomatic stages and the late-onset of MM suggest fundamental differences compared to many other hematopoietic system-related malignancies. The concept discussed in this review is that age-related changes at the level of terminally differentiated plasma cells act as the main risk factors for the development of MM. Epigenetic and genetic changes that characterize both MM development and normal aging are highlighted. The relationships between cellular aging processes, genetic mosaicism in plasma cells, and risk for MM and the stochastic processes contributing to clonal selection and expansion of mutated plasma cells are investigated. In line with the DNA damage accumulation theory of aging, in this review, the evolution of monoclonal gammopathy to symptomatic MM is considered. Therapeutic consequences of age-dependent comorbidities that lead to frailty and have fundamental influence on treatment outcome are described. The importance of considering geriatric states when planning the life-long treatment course of an elderly MM patient in order to achieve maximal therapeutic benefit is emphasized.

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