Management of poor peripheral blood stem cell mobilization: incidence, predictive factors, alternative strategies and outcome. A retrospective analysis on 2177 patients from three major Italian institutions

New strategies for stem cell mobilization

Mobilized peripheral blood (PB) is widely used as source of stem cells (PBSCs) for autologous stem cell transplantation (ASCT). The use of cytokines, alone or in combination with chemotherapy (chemomobilization), is the most common strategy applied to mobilize and collect PBSCs. However, a significant proportion of cancer patients fail to mobilize enough PBSCs to proceed to ASCT. Plerixafor is a small molecule that reversibly and transiently disrupts the interaction between the chemokine receptor CXCR4 and its ligand CXCL12 (formerly known as stroma derived factor 1, SDF-1) leading to the rapid release of CD34⁺ hematopoietic stem cells from the bone marrow (BM) to PB. Plerixafor has been recently approved to enhance PBSC mobilization in adult patients with multiple myeloma or non-Hodgkin lymphoma and has been shown to be more effective than G-CSF alone. There is limited experience on combining plerixafor with chemotherapy plus G-CSF in patients who mobilize poorly. Current evidence suggests that the addition of plerixafor is safe and effective in the large majority of the patients with low blood CD34⁺ cell count after mobilization and/or poor yield after the first collection(s). Circulating CD34⁺ cells can be increased by several folds with plerixafor and the majority of the patients considered “poor mobilizers” can be successfully collected. Overall, its mechanism of action inducing the rapid release of CD34⁺ cells from the BM to the circulation makes plerixafor suitable for the ‘preemptive’ use in patients who are hard-to-mobilize.

A multiple regression analysis on factors influencing haematopoietic progenitor cell collection for autologous transplantation

Autologous hematopoietic stem cell (HSC) transplantation today is the standard treatment for a wide variety of haematological and oncological diseases. HSC are collected from peripheral blood by leukapheresis (HPC-A) following chemotherapy and/or growth factor-mediated mobilization. The ideal HPC-A collection allows to reach the CD34(+) target dose through a single, tailored leukapheresis. The aim of this paper was to find out which collection parameter might play a key role in obtaining a CD34 dose >4×10(6)/kg with a reduced number of leukapheresis. To address this issue, a multivariate logistic regression was carried out on several operational and laboratory parameters from 943 HPC-A collections performed in 600 hematological and oncological patients. We observed a CD34(+) cells collection efficiency (CE) >50% when patient's pre-apheresis total WBC count was lower than 12.5×10(6)/mL. At the same time, the likelihood of reaching the CD34(+) cells target dose/kg increased from 6 to 3 times when the pre-apheresis WBC count ×10(6)/mL t was below 4.3 (OR=6.1; 2.6-14.1) and between 4.3 and 7 (OR=2.8; 1.4-5.7) respectively when compared to a pre-apheresis WBC count >36×10(6)/mL.

Gene expression profiling of dendritic cells in different physiological stages under Cordyceps sinensis treatment

Cordyceps sinensis (CS) has been commonly used as herbal medicine and a health supplement in China for over two thousand years. Although previous studies have demonstrated that CS has benefits in immunoregulation and anti-inflammation, the precise mechanism by which CS affects immunomodulation is still unclear. In this study, we exploited duplicate sets of loop-design microarray experiments to examine two different batches of CS and analyze the effects of CS on dendritic cells (DCs), in different physiology stages: naïve stage and inflammatory stage. Immature DCs were treated with CS, lipopolysaccharide (LPS), or LPS plus CS (LPS/CS) for two days, and the gene expression profiles were examined using cDNA microarrays. The results of two loop-design microarray experiments showed good intersection rates. The expression level of common genes found in both loop-design microarray experiments was consistent, and the correlation coefficients (Rs), were higher than 0.96. Through intersection analysis of microarray results, we identified 295 intersecting significantly differentially expressed (SDE) genes of the three different treatments (CS, LPS, and LPS/CS), which participated mainly in the adjustment of immune response and the regulation of cell proliferation and death. Genes regulated uniquely by CS treatment were significantly involved in the regulation of focal adhesion pathway, ECM-receptor interaction pathway, and hematopoietic cell lineage pathway. Unique LPS regulated genes were significantly involved in the regulation of Toll-like receptor signaling pathway, systemic lupus erythematosus pathway, and complement and coagulation cascades pathway. Unique LPS/CS regulated genes were significantly involved in the regulation of oxidative phosphorylation pathway. These results could provide useful information in further study of the pharmacological mechanisms of CS. This study also demonstrates that with a rigorous experimental design, the biological effects of a complex compound can be reliably studied by a complex system like cDNA microarray.

Poor mobilizer: a retrospective study on proven and predicted incidence according to GITMO criteria

The Italian Group for Bone Marrow Transplantation (Gruppo Italiano Trapianto di Midollo Osseo, GITMO) recently formalized criteria for a shared definition of poor mobilizer in order to facilitate randomized clinical trials and study comparison focusing on the efficacy of current mobilizing regimens. The availability of a standardized tool for poor mobilizer definition suggested us to retrospectively test GITMO criteria feasibility and applicability. Therefore we analyzed medical and laboratory records of adult patients affected by myeloma (MM) or lymphoma undergoing mobilization for autologous peripheral blood HSC collection from January 2010 to June 2011, at Servizio di Emotrasfusione, Istituto di Ematologia, Università Cattolica Del Sacro Cuore, Roma, UOC SIMT AO S. Camillo Forlanini Roma and SIMT Fondazione Policlinico Tor Vergata Roma. We collected data about 227 patients (134 male, 93 female) affected by MM (31.3%) NHL (58.6%) e HD (10.1%). Thirty-nine patients, 21 male and 18 female met proven poor mobilizer criteria definition resulting in a incidence of 17.2% (12.7% in MM, 21.8% in NHL and 4.3% in HD). Eleven patients, seven affected by lymphoma and four affected by myeloma, were defined predicted PM according to major criteria. Eight patients, seven affected by lymphoma and one affected by myeloma, were define predicted PM according to minor criteria. Sixteen out of 39 patients defined as poor mobilizer either according to major or minor criteria underwent collection procedures and eight (20.5%) achieved a cell dose ⩾2×10(6)/kg CD34(+) cells. GITMO criteria application was easy and resulted in poor mobilizer incidence comparable to current literature. Definitions of proven poor mobilizer and predicted poor mobilizer according to major criteria were very effective while minor criteria were less predictive. These results came from a retrospective analysis and therefore should be validated in future prospective trial. On the other hand these data could be an early overall view of the foreseeable future of peripheral blood stem cell collection. In conclusion we believe that these criteria will be able to better characterize poor mobilizer phenomenon and, consequently, to identify patients taking advantage from new mobilizing agents.

Successful stem-cell mobilization and transplantation using plerixafor in a patient with a germ cell tumor

High-dose chemotherapy followed by autologous hematopoietic stem-cell transplantation is an important treatment option for a variety of malignancies. Peripheral blood stem cells (PBSCs) have replaced bone marrow-derived cells as source of stem cells in transplants, and the success of a transplant depends highly on the number of PBSCs mobilized, collected and eventually infused. Nevertheless, a good percentage of patients fail to mobilize stem cells when growth factors alone or in combination with chemotherapy are used. Recently, plerixafor has been approved as a novel agent to mobilize stem cells in multiple myeloma and lymphoma patients. Data on the efficacy and safety of plerixafor in solid tumors is lacking. We report the successful stem cell mobilization and transplantation for a patient with a germ cell tumor using plerixafor.

Who should be really considered as a poor mobilizer in the plerixafor era?

Patients with a number of peripheral CD34+ cells ≥20/μL have recently been defined in the literature as "poor mobilizers". We retrospectively reviewed medical records from a total of 248 patients affected by hematological malignancies or solid tumors undergoing peripheral blood stem cell collection following chemotherapy plus G-CSF. On the basis of the CD34+ cell peak in peripheral blood following mobilization therapy, patients were defined as good mobilizers (group A, CD34+ cells ≥20/μL), relative poor mobilizers (group B, CD34+ cells <20 and ≥8/μL) and absolute poor mobilizers (group C, CD34+ cells <8/μL). One hundred and seventy-seven (71%) patients resulted good mobilizers, 35 (14%) patients relative poor mobilizers and 36 (15%) patients absolute poor mobilizers. Target of stem cell collection was ≥2.0×10(6) CD34+cells/kg for each transplantation procedure. All patients in group A, 20 patients in group B (57%) and 1 patient in group C (2.7%) were able to collect ≥2.0×10(6) CD34+cells/kg. The multivariate analysis confirmed that more than three lines of previous chemotherapy and a previous autologous PBSC transplantation negatively affect mobilization of CD34+ cells in peripheral blood. Our data suggest that a number of CD34+ cells ≥20/μL does not always result in a failed stem cell collection and in fact in our patient series more than 70% of the patients defined as poor mobilizers have indeed collected the minimum number of 2.0×10(6) CD34+cells/kg required for a successful transplantation. The use of new agent such as CXCR4 antagonist plerixafor might further improve mobilization efficacy in such patients.

Predictive factors for inadequate stem cell mobilization in Chinese patients with NHL and HL: 14-year experience of a single-center study

BACKGROUND

Factors affecting progenitor cell mobilization in patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's lymphoma (HL) are incompletely understood. The aim of this retrospective study was to determine which factors are crucial for effective mobilization and collection of autologous peripheral blood stem cells (PBSC) prior to transplantation in Chinese patients.

PATIENTS AND METHODS

A total of 239 patients with lymphoma (198 NHL and 41 HL patients) underwent PBSC collection after mobilization with granulocyte-colony-stimulating factor (G-CSF) or G-CSF plus chemotherapy priming.

RESULTS

Patient characteristics at diagnosis and transplant, including low Eastern Cooperative Oncology Group score (P = 0.013), lack of extranodal invasion (P = 0.034), previously administered radiotherapy regimens (P = 0.040), treatment with platinum prior to mobilization (P = 0.042), previous chemotherapy regimens (P = 0.001) and cycles (P < 0.001), and chemotherapy regimens (P < 0.001) were statistically significant for successful mobilization in multivariate analysis. Premobilization factors, including previous radiotherapy (P = 0.009), previous chemotherapy regimens (P = 0.043) and cycles (P = 0.039), low platelet count prior to mobilization (P = 0.042), and lower CD34+ cells in peripheral blood (PB) (P = 0.050) or bone marrow (BM) (P = 0.007) were considered possibly predictive of poor mobilization. We found the patients who had chemosensitive lymphoma had worse progress-free survival (PFS) than the patients with initial treatment and high risks (P = 0.017).

CONCLUSION

Our analysis showed that high amounts of chemotherapy, radiotherapy, low platelet count, chemosensitive recurrent patients, combination chemotherapy plus G-CSF and low CD34+ cells in BM prior to mobilization could emerged as important predictive factors for mobilization failure in Chinese patients with NHL and HL.

Hematopoietic recovery kinetics predicts for poor CD34+ cell mobilization after cyclophosphamide chemotherapy in multiple myeloma

Autologous stem cell transplantation is an important part of therapy in patients with multiple myeloma. Some patients fail to collect the desired number of stem cells while others require multiple apheresis to reach the desired apheresis target. The aim of this study was to determine the predictive factors and if the hematopoietic kinetics of recovery were predictive for outcome of stem cell mobilization in cyclophosphamide + growth factor (CY-GF) mobilized patients. Three hundred and ninety six consecutive CY-GF mobilization attempts between January 2000 and December 2009 at Mayo Clinic, Rochester, MN were analyzed. Patients were divided into three groups: optimal (>5 × 10(6) CD34/kg), suboptimal (2-5 × 10(6) CD34/kg) and poor (<2 × 10(6) /kg CD34+ cells) mobilization groups. About 86% of patients had optimal stem cell collection, whereas 8% had suboptimal collection and 6% had poor (or failed) collections. Age, Hb, WBC, and platelet levels had an impact on mobilization results. Time to peripheral blood (PB) CD34+cells >10/μL predicted for efficiency of collection and the interval between recovery of WBC>1 post-CY to PB CD34+ cells>10 was shorter in the optimal collection groups. These findings suggest that for patients with a PB CD34+ cell count below 10/μL on Day 13 following CY or 1 day after the WBC>1 × 10(9) /L, addition of plerixafor may be helpful to salvage the mobilization attempt.

Long-Term Outcome after Autologous Stem Cell Transplantation with Adequate Peripheral Blood Stem Cell Mobilization Using Plerixafor and G-CSF in Poor Mobilizer Lymphoma and Myeloma Patients

Poor peripheral blood stem cell (PBSC) mobilization predicts worse outcome for myeloma and lymphoma patients post autologous stem cell transplant (ASCT). We hypothesize that PBSC harvest using plerixafor and G-CSF in poor mobilizers may improve long-term outcome. We retrospectively analyzed the data on patients who had second PBSC mobilization using plerixafor and G-CSF as a rescue. Nine lymphoma and 8 multiple myeloma (MM) patients received the drug. A control group of 25 MM and lymphoma patients who were good mobilizers with G-CSF only was used for comparison. Sixteen of the 17 poor mobilizers proceeded to ASCT, and one MM patient had tandem transplants. Length of hospital stay, infection incidence, granulocyte engraftment, and long-term hematopoietic recovery were not significantly different between the two groups. In conclusion, all poor mobilizers were able to obtain adequate stem cells transplant dose and had similar transplant course and long-term outcome to that of the control good mobilizers group.

The ins and outs of hematopoietic stem cells: studies to improve transplantation outcomes

Deciphering the mechanisms of hematopoietic stem/progenitor cell (HSPC) mobilization and homing is important for the development of strategies to enhance the efficacy of HSPC transplantation and achieve the full potential of HSPC-based cellular therapy. Investigation of these mechanisms has revealed interdependence among the various molecules, pathways and cellular components involved, and underscored the complex nature of these two processes. This review summarizes recent progress in identifying the specific factors implicated in HSPC mobilization and homing, with emphasis on our own work. Particularly, we will discuss our studies on stromal cell-derived factor-1 and its interaction with its receptor CXCR4, proteases (matrix metalloproteinases and carboxypeptidase M), complement proteins (C1q, C3a, C5a, membrane attack complex), sphingosine-1-phosphate, and pharmacologic agents such as the histone deacetylase inhibitor valproic acid and hyaluronic acid.

Treatment of early avascular necrosis of femoral head by small intestinal submucosal matrix with peripheral blood stem cells

BACKGROUND

Avascular necrosis of the femoral head (ANFH) is a highly mutilating disease. There are no effective ways to treat early femoral head ischemia. Peripheral blood stem cell (PBSC) transplantation may be superior to conventional bone marrow transplantation. Small intestinal submucosae matrix (SIS) is composed of highly conserved collagens, glycoproteins, proteoglycans, and glycoaminoglycans in their natural configuration and concentrations. When implanted in a number of microenvironments in vivo, SIS has been used to induce proliferation, remodeling, and regeneration of host tissues. This study was designed to verify the curative effects of PBSC and SIS transplantation-induced vascular regeneration to improve ischemic femoral head necrosis in rabbits.

METHODS

32 New Zealand white rabbits underwent ischemic femoral head necrosis modeling in both hindlimbs by liquid-nitrogen refrigeration. All rabbits were intraperitoneally injected with grannlocytectomy-stimulating factor (250 μg/kg/d), except for normal control subjects injected with equivalent saline solution. After separation of peripheral blood stem cells (PBSCs), 64 femoral heads in 32 rabbits were randomly divided into 4 groups: group A, cancellous bone and peripheral blood stem cells cultured with small intestinal submucosa; group B, cancellous bone and PBSCs; group C, cancellous bone autografts; and group D, no treatment. The specimens were harvested at 4 and 8 weeks after surgery. All specimens were examined to observe angiogenesis and osteogenesis repairing the avascular necrosis of the femoral head by using gross observation, x-ray, histology, and immunohistochemical staining.

RESULTS

In 4 weeks after peripheral stem cell transplantation, the standing ability and activity of the transplanted hindlimbs were improved remarkably, but there were no obvious changes in the control limbs. X-rays showed a greater density of grafts than the host bone in groups A,B, and group C was unchanged at 4 weeks. Histology revealed many osteoprogenitor cells and osteoblasts and no inflammatory cell infiltration at 4 weeks with much new bone formed at 8 weeks in group A and at 4 weeks in group B. The cancellous bone autograft was absorbed completely at 8 weeks in group C. There was little osteoid tissue formed in group D at 8 weeks. The zone of new bone formation in group A was greater than that in group B (P < .05), but there was no significant difference between groups A and C (P > .05). Immunohistochemical staining with CD31 mouse antibody showed greater amounts and zones of new blood vessels in groups A and B at 4 and 8 weeks and little evidence in group D. There was no significant difference between groups A and B (P > .05) and significant differences between groups A and B versus C and D (P < .05).

CONCLUSION

Transplantation of PBSCs cultured with SIS effectively improved ischemic femoral head necrosis.

Hematopoietic stem cells from poor and good mobilizers are qualitatively equivalent

BACKGROUND

Marrow damage from chemo- and radiation therapies has been suggested to affect quality and quantity of hematopoietic stem cell (HSC) products. We tested the hypothesis that CD34+ cells (HSCs) from low mobilizers are qualitatively inferior to HSCs from high mobilizers.

STUDY DESIGN AND METHODS

HSC quality was defined by proportion of primitive HSC subsets (CD34+CD38-, CD34+HLA-DR-, and CD34+ in G0 stage of cell cycle), the proportion of HSCs that express CXCR4 and CD26 homing proteins, and days to neutrophil and platelet (PLT) engraftments after transplant. HSC content and CD34 subsets analyses were performed using flow cytometry following the ISHAGE protocol. We evaluated the HSC quantity and quality of 139 autologous filgrastim-mobilized HSC products. Patients were categorized into low, moderate, and high mobilizers if their total HSC collection was less than 3 × 10(6), 3 × 10(6) or more and less than 5 × 10(6), and 5 × 10(6)/kg or more, respectively.

RESULTS

The median number of primitive CD34 subsets increases with increasing HSC numbers and this association was significant (p = 0.001). However, when the ratios of the primitive CD34 subsets to total HSC counts were compared among the mobilization groups, the ratios were not significantly different. Coexpression of neither CD26 nor CXCR4 with CD34 antigen correlated with HSC mobilization. Evaluation of days to neutrophil engraftment among the mobilization groups did not show a significant difference (p = 0.1). However, days to PLT engraftment among the mobilization groups was significantly different (p = 0.05).

CONCLUSION

The quality of HSCs from low mobilizers was comparable to HSCs from high mobilizers.

Factors affecting autologous peripheral blood hematopoietic stem cell collections by large-volume leukapheresis: a single center experience

OBJECTIVE

To evaluate factors affecting peripheral blood hematopoietic stem cell yield in patients undergoing large-volume leukapheresis for autologous peripheral blood stem cell collection.

METHODS

Data from 304 consecutive autologous peripheral blood stem cell donors mobilized with hematopoietic growth factor (usually G-CSF), associated or not with chemotherapy, at Hospital Israelita Albert Einstein between February 1999 and June 2010 were retrospectively analyzed. The objective was to obtain at least 2 × 106 CD34+ cells/kg of body weight. Pre-mobilization factors analyzed included patient's age, gender and diagnosis. Post mobilization parameters evaluated were pre-apheresis peripheral white blood cell count, immature circulating cell count, mononuclear cell count, peripheral blood CD34+ cell count, platelet count, and hemoglobin level. The effect of pre and post-mobilization factors on hematopoietic stem cell collection yield was investigated using logistic regression analysis (univariate and multivariate approaches).

RESULTS

Pre-mobilization factors correlating to poor CD34 + cell yield in univariate analysis were acute myeloid leukemia (p = 0.017) and other hematological diseases (p = 0.023). Significant post-mobilization factors included peripheral blood immature circulating cells (p = 0.001), granulocytes (p = 0.002), hemoglobin level (p = 0.016), and CD34+ cell concentration (p < 0.001) in the first harvesting day. However, according to multivariate analysis, peripheral blood CD34+ cell content (p < 0.001) was the only independent factor that significantly correlated to poor hematopoietic stem cell yield.

CONCLUSION

In this study, peripheral blood CD34+ cell concentration was the only factor significantly correlated to yield in patients submitted to for autologous collection.

Proposed definition of 'poor mobilizer' in lymphoma and multiple myeloma: an analytic hierarchy process by ad hoc working group Gruppo ItalianoTrapianto di Midollo Osseo

Many lymphoma and myeloma patients fail to undergo ASCT owing to poor mobilization. Identification of poor mobilizers (PMs) would provide a tool for early intervention with new mobilization agents. The Gruppo italianoTrapianto di Midollo Osseo working group proposed a definition of PMs applicable to clinical trials and clinical practice. The analytic hierarchy process, a method for group decision making, was used in setting prioritized criteria. Lymphoma or myeloma patients were defined as ‘proven PM' when: (1) after adequate mobilization (G-CSF 10 μg/kg if used alone or ⩾5 μg/kg after chemotherapy) circulating CD34⁺ cell peak is <20/μL up to 6 days after mobilization with G-CSF or up to 20 days after chemotherapy and G-CSF or (2) they yielded <2.0 × 10⁶ CD34⁺ cells per kg in ⩽3 apheresis. Patients were defined as predicted PMs if: (1) they failed a previous collection attempt (not otherwise specified); (2) they previously received extensive radiotherapy or full courses of therapy affecting SC mobilization; and (3) they met two of the following criteria: advanced disease (⩾2 lines of chemotherapy), refractory disease, extensive BM involvement or cellularity <30% at the time of mobilization; age ⩾65 years. This definition of proven and predicted PMs should be validated in clinical trials and common clinical practice.

Peripheral blood stem cell transplantation for ischemic femoral head necrosis

BACKGROUND

Avascular necrosis of the femoral head (ANFH) is a highly mutilating disease. There is no effective way to treat femoral head ischemia. This study was designed to show the curative effects of peripheral blood stem cell transplantation to induce vascular regeneration and improve ischemic femoral head necrosis in rabbits.

METHODS

Twenty New Zealand white rabbits underwent ischemic femoral head necrosis in both hindlimbs using liquid-nitrogen refrigeration. One cohort of rats was intraperitoneally injected with granulocyte-specific colony-stimulating factor (250 microg/kg/d), and control animals received equivalent saline solution. The right side was used as the transplantation group and the left as the control. After separation of peripheral blood, a stem cell suspension was poured into the right femoral artery and saline solution into the left femoral artery.

RESULTS

At 4 weeks after peripheral stem cell transplantation, standing ability and activity of the the transplanted right hindlimb were remarkably improved, but there were no obvious changes in the control limbs. The experimental rabbits underwent arteriography of bilateral femoral heads, which indicated increased and thickened blood supply to the transplanted right hindlimb compared with the left control.

CONCLUSION

Peripheral blood stem cell transplantation improved ischemic femoral head necrosis.

Recent advances on the use of the CXCR4 antagonist plerixafor (AMD3100, Mozobil™) and potential of other CXCR4 antagonists as stem cell mobilizers

AMD3100 was originally discovered as an anti-HIV agent effective in inhibiting the replication of HIV in vitro at nanomolar concentrations. We found it to be a potent and selective antagonist of CXCR4, the receptor for the chemokine SDF-1 (now called CXCL12). AMD3100 was then developed, and marketed, as a stem cell mobilizer, and renamed plerixafor (Mozobil™). The path to the discovery of Mozobil™ as a stem cell mobilizer was described in Biochem. Pharmacol. 77: 1655-1664 (2009). Here I review the recent advances that have consolidated the role of plerixafor in mobilizing hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) from the bone marrow into the blood circulation. Plerixafor acts synergistically with granulocyte colony-stimulating factor (G-CSF), and its usefulness has been proven particularly for the mobilization of HSCs and HPCs for autologous stem cell transplantation in patients with non-Hodgkin's lymphoma (NHL) or multiple myeloma (MM). Plerixafor also has great potential for the treatment of hematological malignancies other than NHL and MM, and non-hematological malignancies, and, eventually, several other diseases depending on the CXCL12-CXCR4 interaction. Various AMD3100 analogs have been described (i.e. AMD11070, AMD3465, KRH-3955, T-140, and 4F-benzoyl-TN14003), primarily as potential anti-HIV agents. They are all strong CXCR4 antagonists. Their role in stem cell mobilization remains to be assessed.

Clinical impact and resource utilization after stem cell mobilization failure in patients with multiple myeloma and lymphoma

High-dose chemotherapy in conjunction with auto-SCT is the preferred treatment of relapsed Hodgkin disease and non-Hodgkin lymphoma and newly diagnosed multiple myeloma. Failure to achieve optimal stem cell mobilization results in multiple subsequent attempts, which consumes large amounts of growth factors and potentially requires antibiotics and transfusions. We retrospectively reviewed the natural history of stem cell mobilization attempts at our institution from 2001 to 2007 to determine the frequency of suboptimal mobilization in patients with hematologic malignancy undergoing autologous transplant and analyzed the subsequent resource utilization in patients with initially failed attempts. Of 1775 patients undergoing mobilization during the study period, stem cell collection (defined by the number of CD34+ cells/kg) was 'optimal' (> or = 5 x 10(6)) in 53%, 'low' (> or = 2-5 x 10(6)) in 25%, 'poor' (<2 x 10(6)) in 10%, and 'failed' (<10 CD34+ cells/microl) in 12%. In the 47% of collections that were less than optimal, increased resource consumption included increased use of growth factors and antibiotics, subsequent chemotherapy mobilization, increased transfusional support, more apheresis procedures, and more frequent hospitalization. This usually unappreciated resource utilization associated with stem cell mobilization failure highlights the need for more effective mobilization strategies.