Preferential sensitivity of hematopoietic (HPs) and mesenchymal (MPs) progenitors to fludarabine suggests impaired bone marrow niche and HP mobilization

Higher Age (≥60 Years) Increases the Risk for Adverse Events during Autologous Hematopoietic Stem Cell Transplantation

Autologous hematopoietic stem cell transplantation (autoHSCT) is a standard of care for patients with hemato-oncologic diseases. This procedure is highly regulated, and a quality assurance system needs to be in place. Deviations from defined processes and outcomes are reported as adverse events (AEs: any untoward medical occurrence temporally associated with an intervention that may or may not have a causal relationship), including adverse reactions (ARs: a response to a medicinal product which is noxious and unintended). Only a few reports on AEs cover the procedure of autoHSCT from collection until infusion. Our aim was to investigate the occurrence and severity of AEs in a large data set of patients who were treated by autoHSCT. In this retrospective, observational, single-center study on 449 adult patients during the years 2016-2019, AEs occurred in 19.6% of the patients. However, only 6.0% of patients had ARs, which is a low rate compared to the percentages (13.5-56.9%) found in other studies; 25.8% of the AEs were serious and 57.5% were potentially serious. Larger leukapheresis volumes, lower numbers of collected CD34+ cells and larger transplant volumes significantly correlated with the occurrence and number of AEs. Importantly, we found more AEs in patients >60 years (see graphical abstract). By preventing potentially serious AEs of quality and procedural issues, AEs could be reduced by 36.7%. Our results provide a broad view on AEs and point out steps and parameters for the potential optimization of the autoHSCT procedure, especially in elderly patients.

Optimizing mobilization strategies in difficult-to-mobilize patients: The role of plerixafor

Peripheral blood stem cell collection is currently the most widely used source for hematopoietic autologous transplantation. Several factors such as advanced age, previous chemotherapy, disease and marrow infiltration at the time of mobilization influence the efficacy of CD34(+) progenitor cell mobilization. Despite the safety and efficiency of the standard mobilization protocols (G-CSF ± chemotherapy), there is still a significant amount of mobilization failure rate (10-40%), which necessitate novel agents for effective mobilization. Plerixafor, is a novel agent, has been recently approved for mobilization of hematopoietic stem cells (HSCs). The combination of Plerixafor with G-CSF provides the collection of large numbers of stem cells in fewer apheresis sessions and can salvage those who fail with standard mobilization regimens. The development and optimization of practical algorithms for the use Plerixafor is crucial to make hematopoietic stem cell mobilization more efficient in a cost-effective way. This review is aimed at summarizing how to identify poor mobilizers, and define rational use of Plerixafor for planning mobilization in hard-to-mobilize patients.

Peripheral blood stem cell mobilization failure

Autologous hematopoietic stem cell transplantation (HSCT) is an important and often life saving treatment for many hematological malignancies and selected solid tumors. To rescue hematopoiesis after high-dose chemotherapy in autologous HSCT depends on maintaining sufficient stem cells. Hematopoietic stem cells and progenitor cells expressing CD34 in the BM are mobilized into the circulation with granulocyte-colony stimulating factor ± chemotherapy prior to autologous HSCT. One of the most important factors for success of autologous HSCT is hematopoietic stem cell (HSC) count. Minimum threshold for the engraftment of hematopoietic cells is accepted as 2 × 10(6) CD34 + cells/kg especially for platelet engraftment. Below this level it is defined as stem cell mobilization failure. There are several factors affecting stem cell mobilization: prior chemotherapy (such as fludarabine, melphalan, lenalidomide) and radiotherapy, age, type of disease, bone marrow cellularity. We tried to summarize the reasons of peripheral stem cell mobilization failure.

Plerixafor to the rescue: boosting peripheral blood stem cell mobilization in patients previously treated with hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone/methotrexate, cytarabine (Hyper-CVAD) chemotherapy

Hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone/methotrexate, cytarabine (Hyper-CVAD) chemotherapy exerts deleterious effects on peripheral blood stem cell (PBSC) mobilization. We retrospectively reviewed the use of plerixafor to salvage mobilization in 18 Hyper-CVAD treated patients who initially mobilized poorly with chemotherapy and granulocyte colony stimulating factor (G-CSF). After plerixafor administration the median peripheral blood (PB) CD34 + count rose from 3.74/μL (0-17/μL) to 6.85/μL (0-47.2/μL). The patients collected a median of 1.64 (0.21-5.56) × 10(6) CD34 + cells/kg with a median number of 3 (1-4) doses in the same collection cycle, and 11 patients reached the 2.0 × 10(6) CD34 + cells/kg minimum required for transplant. Six patients were remobilized later with G-CSF and plerixafor, and three additional patients reached this goal. For these 14 patients the median number of doses of plerixafor required to reach 2.0 × 10(6) CD34 + cells/kg was 3 (range 1-4). In conclusion, plerixafor can be utilized successfully in many cases to overcome the effects of Hyper-CVAD on PBSC mobilization.

The effect of chemotherapy on telomere dynamics: clinical results and possible mechanisms

Telomeres are the chromosomal end components, and their length in hematopoietic stem cells correlates with the bone marrow proliferative reserve. There are few data regarding telomere dynamics in hematopoietic stem cells after exposure to chemotherapy. We show that the attrition of telomeres after cytotoxic treatment correlates with the intensity of chemotherapy. Using cytotoxic drugs with differential effects on hematopoietic stem cells, our data imply that chemotherapy-induced telomere shortening results from direct damage to hematopoietic stem cells and/or the induction of proliferative stress on bone marrow while sparing repopulating stem cells. These results gain importance considering the current long survival of patients with cancer.

Predictive factors for poor peripheral blood stem cell mobilization and peak CD34(+) cell count to guide pre-emptive or immediate rescue mobilization

BACKGROUND AIMS

Failure in mobilization of peripheral blood (PB) stem cells is a frequent reason for not performing hematopoietic stem cell transplantation (HSCT). Early identification of poor mobilizers could avoid repeated attempts at mobilization, with the administration of pre-emptive rescue mobilization.

METHODS

Data from the first mobilization schedule of 397 patients referred consecutively for autologous HSCT between 2000 and 2010 were collected. Poor mobilization was defined as the collection of < 2 × 10(6) CD34(+)cells/kg body weight (BW).

RESULTS

The median age was 53 years (range 4-70) and 228 (57%) were males. Diagnoses were multiple myeloma in 133 cases, non-Hodgkin's lymphoma in 114, acute myeloid leukemia or myelodysplastic syndrome in 81, Hodgkin's lymphoma in 42, solid tumors in 17 and acute lymphoblastic leukemia in 10. The mobilization regimen consisted of recombinant human granulocyte-colony-stimulating factor (G-CSF) in 346 patients (87%) and chemotherapy followed by G-CSF (C + G-CSF) in 51 (13%). Poor mobilization occurred in 105 patients (29%), without differences according to mobilization schedule. Diagnosis, previous therapy with purine analogs and three or more previous chemotherapy lines were predictive factors for poor mobilization. A CD34(+)cell count in PB > 13.8/μL was enough to ensure ≥ 2 × 10(6) CD34(+)cells/kg, with high sensitivity (90%) and specificity (91%).

CONCLUSIONS

The prevalence of poor mobilization was high, being associated with disease type, therapy with purine analogs and multiple chemotherapy regimens. The threshold of CD34(+) cell count in PB identified poor mobilizers, in whom the administration of immediate or pre-emptive plerixafor could be useful to avoid a second mobilization.

How I treat patients who mobilize hematopoietic stem cells poorly

Transplantation with 2-5 × 106 mobilized CD34+cells/kg body weight lowers transplantation costs and mortality. Mobilization is most commonly performed with recombinant human G-CSF with or without chemotherapy, but a proportion of patients/donors fail to mobilize sufficient cells. BM disease, prior treatment, and age are factors influencing mobilization, but genetics also contributes. Mobilization may fail because of the changes affecting the HSC/progenitor cell/BM niche integrity and chemotaxis. Poor mobilization affects patient outcome and increases resource use. Until recently increasing G-CSF dose and adding SCF have been used in poor mobilizers with limited success. However, plerixafor through its rapid direct blockage of the CXCR4/CXCL12 chemotaxis pathway and synergy with G-CSF and chemotherapy has become a new and important agent for mobilization. Its efficacy in upfront and failed mobilizers is well established. To maximize HSC harvest in poor mobilizers the clinician needs to optimize current mobilization protocols and to integrate novel agents such as plerixafor. These include when to mobilize in relation to chemotherapy, how to schedule and perform apheresis, how to identify poor mobilizers, and what are the criteria for preemptive and immediate salvage use of plerixafor.

Fludarabine as a risk factor for poor stem cell harvest, treatment-related MDS and AML in follicular lymphoma patients after autologous hematopoietic cell transplantation

Fludarabine is an effective treatment for follicular lymphoma (FL), but exposure to it negatively impacts stem cell mobilization and may increase the risk of subsequent myelodysplastic syndrome and acute myelogenous leukemia (t-MDS/AML). We hypothesized that the risk that fludarabine imparts to stem cell mobilization and t-MDS/AML would be affected by dose or timing. All patients with FL treated at Cleveland Clinic from 1991 to 2007 with autologous hematopoietic cell transplantation were evaluated. Recursive partitioning analysis was used to explore associations of fludarabine and mitoxantrone dose and timing with poor stem cell harvest and t-MDS/AML. We identified 171 patients, of whom 52 previously received fludarabine. Patients exposed to fludarabine prior to auto-HCT were more likely to require >5 days of leukapheresis (P<0.001) and second stem cell mobilization (P<0.001), especially at a cumulative dose >150 mg/m(2). Univariable risk factors for t-MDS/AML included the number of chemotherapy regimens before auto-HCT, the need for >5 days of leukapheresis to collect CD34+ cells and fludarabine exposure in a dose-dependent manner, particularly when >500 mg/m(2). A cumulative dose of fludarabine >150 mg/m(2) increases the risk for poor stem cell harvests and any exposure increases the risk of t-MDS/AML, with the greatest risk being at doses >500 mg/m(2).

Efficacious but insidious: a retrospective analysis of fludarabine-induced myelotoxicity using long-term culture-initiating cells in 100 follicular lymphoma patients

OBJECTIVE

Fludarabine has been recognized as effective treatment in patients with follicular lymphoma (FL), but can induce myelotoxicity of unknown mechanism.

MATERIALS AND METHODS

Myelotoxicity was assessed by cultivation of two types of hematopoietic progenitor cells: colony-forming units granulocyte-macrophage (CFU-GM) and long-term culture-initiating cells (LTC-IC). Pretreatment amounts of CFU-GM and LTC-IC were correlated to age, gender, stage of disease, bone marrow involvement, and previous therapy. Posttreatment comparison of CFU-GM and LTC-IC was performed after different regimens of chemotherapy: fludarabine-based (FND +/- R), procarbazine-based (COPP +/- R), and CHOP(cyclophosphamide, doxorubicin, vincristine, prednisone) +/- R(Rituximab).

RESULTS

One-hundred patients (median age 55 years; 21 patients relapsed) treated for FL were analyzed. The total number of progenitor hematopoietic cells in both types of cultures varied in wide ranges; for LTC-IC between 0 and 874 cells/mL with a median of 77.71 cells/mL and for CFU-GM between 0 and 531 x 10(2) cells/mL with a median of 30.58 x 10(2) cells/mL. Bone marrow involvement, gender, stage of disease, or previous therapy had no influence on LTC-IC and CFU-GM counts. We identified an increase in LTC-IC, but not CFU-GM, associated with age (p = 0.01). Median figures for CFU-GM and LTC-IC were found to be significantly lower after FND +/- R and COPP +/- R than after CHOP +/- R therapy, compared to baseline values (p < 0.01).

CONCLUSIONS

Fludarabine and procarbazine have a dramatic influence, especially on the most immature hematopoietic cells, mirrored in reduced numbers of LTC-IC. This finding is consistent with clinical observations (poor mobilization after fludarabine) and offers an insight into the mechanism of fludarabine-induced myelotoxicity.