Cytopenia at Diagnosis Impairs Stem Cell Mobilization Among Patients with Multiple Myeloma

Introduction:

The GIMEMA group has recently developed a risk score predicting mobilization failure (Musto et al, EHA 2014). The risk score included age, cytopenia at diagnosis, induction therapy and their toxicity. In this study we aimed to evaluate the impact of these factors on peripheral blood stem cell (PBSC) mobilization among patients with multiple myeloma (MM).

Patients and methods:

125 newly diagnosed patients with MM (M: 76, F: 49) planned for autologous stem cell transplantation; median age 58 years (range, 30-67) were included in the analysis. This retrospective study examined the impact of age (> 60 years), gender of the patients, cytopenia (Hb<10 gr/dL, absolute neutrophil count < 1x10⁹/L, thrombocyte count < 100x10⁹/L) at diagnosis, and severe hematological toxicity during induction therapy, the type of induction and mobilization methods, the presence of neuropathy, comorbid diseases such as diabetes mellitus, hypertension and renal failure (creatinine > 2 mg/dL), and the use of beta blocker drugs. Patients with CD34⁺ levels of <20/μL in peripheral blood at maximum stimulation were considered to be Poor Mobilizers. The total amount of PBSC <5x10⁶/kg after a single mobilization procedure was defined as sub-optimal collection. Poor mobilization was observed in only two patients (<2x10⁶/kg). Statistics: Comparison of categorical variables was evaluated by chi-square test or Fisher exact test. Nominal variables were compared with non-parametrical test, Mann-Whitney U or Kruskal Wallis test. P value below as 0.05 was accepted as significance.

Results:

Optimal mobilization with median two apheresis (1-4) sessions for PBSC was obtained in 85.6% of the patients (n=107). Median CD34⁺ cells in this group were 8.33x10⁶/kg (5-27x10⁶/kg). The presence of cytopenia at diagnosis was the only significantly detrimental factor on mobilization (90% vs 77.1%, p=0.04). When the patients was scored in four groups as having single or combined variables (age, cytopenia at the diagnosis or during induction therapy), we were not able to develop a risk score.

Conclusions:

In our experience, 14.4% of the myeloma patients showed suboptimal or poor mobilization. Use of bortezomib, age, presence of neurotoxicity or hematological toxicity at mobilization did not significantly impair mobilization. We were able to confirm only cytopenia at diagnosis, from the four factors reported by Musto et al, as a detrimental factor impairing the stem cell mobilization.