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We here report final results of a phase II/III prospective study that evaluated in Multiple Myeloma the use of on-demand plerixafor (PLX) added to mobilizing chemotherapy for patients showing predictive signs of mobilization failure. A total of 111 patients with MM were registered, all received cyclophosphamide 4 g/m2and granulocyte colony-stimulating factor (G-CSF). Overall, a successful CD34+ cell mobilization was achieved in 97.2% (108/111) of patients. Minimum harvest (≥2.0 × 106CD34+ cells/kg) was achieved in 97.2% (108/111) and optimal harvest success (≥4.0 × 106CD34+ cells/kg) was achieved in 84.6% (94/111). Multivariate analysis showed that patients who received on-demand PLX treatment had significantly higher likelihoods of successfully achieving both the minimal (p = .006) and optimal harvest (p = .05) in respect to a historical control group mobilized without any PLX. The incremental cost-effectiveness ratio, for each 1% increase in probability of achieving a successful minimal harvest, was€40.6 per patient. [ABSTRACT FROM AUTHOR]

A high number of CD34+ cells in the peripheral blood during mobilization in patients with acute myeloid leukemia (AML) in complete remission (CR) is associated with a high relapse rate. The variability in chemoresistance of normal bone marrow precursors has been hypothesized as explanation for the variable CD34 mobilization in AML. In 37 patients with AML in CR, we determined the chemosensitivity of bone marrow clonogenic precursors to maphosphamide and etoposide, which was then correlated with the degree of CD34+ mobilization. In an enlarged set of 49 patients, we also studied the importance of chemosensitivity of marrow precursors for disease-free survival and relapse incidence. Significant correlations were demonstrated between the peak number of CD34+ cells and residual growth of colony-forming unit granulocyte-macrophage (CFU-GM) after maphosphamide (R = 0.550; p = 0.0003) and after etoposide (R = 0.793; p = 0.0003). It was possible to identify three groups of AML patients based on chemosensitivity. The mean CD34+ peak was 33 × 106/L in the hyperchemosensitive group, 141 × 106/L in the normochemosensitive (p = 0.03), and 379 × 106/L in the chemoresistant group (p = 0.002). Failed CD34+ mobilization was observed in 72% of the hyperchemosensitive group, 23% of the normochemosensitive group, and 0% of the chemoresistant group (p = 0.001). Hyperchemosensitivity of CFU-GM, together with a low platelet count, were independent factors important in the failure of CD34+ cell mobilization. A disease-free survival significantly inferior to that of all other patients was associated with chemoresistance of CFU-GM (log rank, p = 0.030) and with chemoresistance of burst-forming unit erythroid (BFU-E) (log rank, p = 0.033). Chemoresistance of CFU-GM (p = 0.048) and BFU-E (p = 0.017) was also associated with increase relapse incidence. Nonleukemic nature of these precursors was demonstrated studying minimal residual disease from single colony cells. In conclusion, we found that hyperchemosensitivity of normal nonleukemic CFU-GM is associated with a high risk of CD34+ cell mobilization failure, while a chemoresistant pattern in CFU-GM and BFU-E is associated with poor disease-free survival and increased cumulative incidence of relapse. [Copyright &y& Elsevier]

High-dose melphalan plus autologous stem cell transplantation (ASCT) is a standard of care for transplant-eligible patients with newly diagnosed multiple myeloma (NDMM), and adequate hematopoietic stem cell (HSC) collection is crucial to ensure hematologic recovery after ASCT. In this prospective, observational study we evaluated HSC mobilization with granulocyte colony-stimulating factor (G-CSF), cyclophosphamide, and 'on-demand' plerixafor (in patients with <20×106 CD34+ cells/L after at least 4 days of G-CSF or failing to collect ≥1×106 CD34+ cells/kg after the first apheresis) in NDMM patients treated with novel agent-based induction therapy. The primary endpoint was the rate of poor mobilizers (patients collecting <2×106 CD34+ cells/kg or requiring plerixafor rescue to reach an adequate HSC harvest). Secondary endpoints included the rate of patients collecting ≥2×106 CD34+ cells/kg after plerixafor administration and the identification of factors predicting mobilization failure or plerixafor need. Overall, 301 patients (median age 60 years) were enrolled. Two hundred and eighty-seven of 301 (95%) and 274 of 301 (93%) patients collected ≥2×106 and ≥4×106 CD34+ cells/kg, respectively, with a median of 9.9×106 CD34+ cells/kg collected. Poor mobilizers were 48 of 301 (16%): 34 of 301 (11%) required plerixafor rescue, and 14 of 301 (5%) failed HSC collection regardless of plerixafor. Thirty-four of 38 (90%) patients receiving plerixafor collected ≥2×106 CD34+ cells/kg. Bone marrow plasmacytosis at diagnosis >60% (odds ratio [OR]=4.14), lenalidomide use (OR=4.45), and grade 3-4 hematologic toxicities during induction (OR=3.53) were independently associated with a higher risk of mobilization failure or plerixafor need. Cyclophosphamide plus G-CSF and 'on-demand' plerixafor is an effective strategy in NDMM patients treated with novel agents, resulting in a high rate of HSC collection and high HSC yield (clinicaltrials gov. identifier: NCT03406091).

Background: Early identification of predictive factors of failure to mobilise CD34+ cells could enable rational use of plerixafor during first mobilisation, avoiding the need for a second mobilisation course. However, "on demand" administration of plerixafor needs to be driven by established parameters to avoid inappropriate use., Materials and Methods: To address this issue, we studied the value of the peripheral blood CD34+ count, measured early (on days +10, +11, +12 and +13), in predicting the mobilisation outcome in the ensuing days. We retrospectively collected data from three Italian centres on 233 patients affected by multiple myeloma or lymphoma who underwent a first or second attempt at mobilisation with cyclophosphamide 4 g/m(2) and granulocyte colony-stimulating factor. To assess the diagnostic value of peripheral blood white blood cell and CD34+ cell counts with respect to "mobilisation failure", we considered failed mobilisation as "disease" and the CD34+ cell count in peripheral blood, on a specific day, as a "diagnostic test". For various thresholds, we measured sensitivity, false positive rate, specificity and positive predictive value (PPV) as well as the area under the receiver-operating characteristic curves (AUC)., Results: A CD34+ cell count <10 × 10(6)/L on day 13 had high sensitivity (1.00) and high specificity (1.00) for predicting subsequent mobilisation failure, with an AUC of 1.0. However, good prediction was also obtained using a lower threshold (CD34+ cell count: <6 × 10(6)/L) at an earlier time (day 12). The PPV of the day 13 threshold was 1.00 while that of the day 12 one was 0.87., Discussion: We propose that patients with <6 × 10(6)/L CD34+ cells in peripheral blood on day 12 and <10 × 10(6)/L on day 13 following mobilisation with cyclophosphamide 4 g/m(2) and granulocyte colony-stimulating factor are candidates for "on demand" use of plerixafor, making the administration of this expensive agent more efficient and avoiding its inappropriate use.