Early Lymphocyte Recovery Predicts Superior Survival after Autologous Hematopoietic Stem Cell Transplantation for Patients with Primary Systemic Amyloidosis
Clinical Cancer Research | June 11, 2022 | Volume: 11 | Issue: 3 | Pages: 1210-1218
AbstractPurpose: Absolute lymphocyte count recovery at day 15 (ALC-15) post-autologous stem cell transplantation (ASCT) is a powerful prognostic indicator for survival for multiple hematologic malignancies and metastatic breast cancer. The relationship of ALC-15 with clinical outcomes in primary systemic amyloidosis is unknown.Experimental Design: We evaluated 145 consecutive patients with primary systemic amyloidosis who underwent ASCT at the Mayo Clinic from 1996 to 2003. The ALC-15 threshold was set at 500 cells/μL based on our previous observations.Results: The median patient follow-up was 22 months (range, 3-87 months). Higher hematologic complete response was observed in patients with an ALC-15 ≥ 500 cells/μL compared with patients with an ALC-15 < 500 cells/μL (41% versus 21%, P < 0.0008, respectively). The median overall survival and progression-free survival times were significantly better for the 59 patients that achieved an ALC-15 ≥ 500 cells/μL compared with 86 patients with ALC-15 < 500 cells/μL (not reached versus 53 months, P < 0.0003 and not reached versus 27 months, P < 0.0001, respectively). Multivariate analysis showed ALC-15 to be an independent prognostic factor for overall survival and progression-free survival.Conclusions: ALC-15 ≥ 500 cells/μL is associated with significantly improved clinical outcomes following ASCT in patients with primary systemic amyloidosis.
Effect of AMD3100 on T Lymphocyte Subpopulations in Apheresis Products of Patients Undergoing Autologous Hematopoietic Stem Cell Transplantation for Non Hodgkin Lymphoma.
Abstract AMD3100, a CXCR4 receptor antagonist, has been studied as a stem cell mobilization agent for the purpose of autologous stem cell transplantation (ASCT) in hematologic malignancies. Lymphocyte subset analysis of peripheral blood in patients treated with AMD3100 has been studied in healthy volunteers. To date, no reports exist describing the lymphocyte subsets of the autograft in patients undergoing AMD3100 stem cell mobilization for the purposes of ASCT in non-Hodgkin lymphoma (NHL). Considering our prior work demonstrating the significant impact of autograft lymphocyte content on clinical outcomes of patients undergoing ASCT for NHL we set out to profile autograft lymphocyte subsets of patients undergoing mobilization with AMD3100. Using flow cytometry, we analyzed aliquots of apheresis products in 7 patients with NHL undergoing AHSCT who received AMD3100 in addition to G-CSF as a part of their mobilization regimen. These results were compared to 29 patients with NHL who had undergone stem cell mobilization with G-CSF alone. There were no significant differences between these two groups of patients in terms of sex, age, performance status, histology, LDH, and number of pretransplant chemotherapeutic regimens. CD34+ cells collected at apheresis did not differ significantly between the groups. However, compared with G-CSF alone, patients that received AMD3100 had an approximate 5-fold increase in CD4+ cells (0.62 x 109 cells/kg vs. 0.12 x 109 cells/kg, p = 0.0004), a 3.5-fold increase in the absolute number of autograft CD3+ cells (1.21 x 109 cells/kg vs. 0.33 x 109 cells/kg, p = 0.0017), and a 2.5-fold increase in CD8+ cells (0.48 x 109 cells/kg vs 0.19 x 109 cells/kg, p = 0.215). A significant increase was also noted in CD4+25+ cell compartment (0.17 x 109 cells/kg vs. 0.006 x 109 cells/kg, p = 0.0001). No significant difference was noted in the absolute number of autograft CD16+56+ NK cells. Finally, an increase in the autograft total absolute lymphocyte count (41.6 x 109 cells/kg vs. 2.88 x 109 cells/kg, p < 0.001) as well as peripheral blood absolute lymphocyte count at day 15 after AHSCT was observed in those patients who had received AMD3100 (0.79 x 109 cells/kg vs. 0.58 x 109 cells/kg, p = 0.04). The increased lymphocyte content of the autograft (total and subset) would suggest the potential of positive impact on clinical outcomes in patients mobilized with AMD3100. Indeed, none of the patients who received AMD3100 had relapsed disease at one year post-transplant (although two of these patients are currently 9 months and 11 months post-transplant respectively), whereas 10 of the 29 control patients had relapsed disease at one year. Further studies are necessary to confirm these observations and ascertain their clinical significance.
Early Lymphocyte Recovery after Autologous Stem Cell Transplantation Predicts Superior Survival in Mantle Cell Lymphoma.
Abstract Mantle-cell lymphoma (MCL) is characterized by an aggressive clinical course and poor prognosis with a median survival of only 3 to 4 years. High dose chemotherapy followed by autologous stem cell transplantation (ASCT) is an effective treatment strategy for MCL demonstrating significantly prolongs progression free survival (PFS) when compared to IFNa maintenance therapy of patients in first remission. We have previously shown that absolute lymphocyte count at day 15 (ALC-15) after ASCT is an independent prognostic factor for survival in hematologic malignancies (non-Hodgkin’s lymphoma (NHL), Hodgkin’s disease, multiple myeloma, primary amyloidosis, acute myelogenous leukemia) and breast cancer. The study of ALC-15 after ASCT as a prognosis factor in NHL included different subtypes of lymphomas. The relationship of ALC-15 after ASCT in patients with MCL has not been specifically addressed. Herein we present data evaluating the impact of early lymphocyte recovery (ALC-15) in patients undergoing ASCT for MCL. We retrospectively reviewed the medical records of 42 consecutive patients (9 females and 33 males) with MCL who underwent ASCT at the Mayo Clinic in Rochester from 1993 to 2005. Based on our previous studies, the ALC-15 threshold was set at 500 cells/μL. The median patient age at transplant was 57 years (range, 37–71) and the median follow-up after ASCT was 25 months (range, 2–106 months). The median overall (OS) and PFS times were significantly better for the 24 patients that achieved an ALC-15 ≥ 500 cells/mL compared with 18 patients with ALC-15 < 500 cells/μL (not reached versus 30 months, P < 0.01 and not reached versus 16 months, P < 0.0006, respectively). Multivariate analysis adjusting for other prognostic factors suggests that ALC-15 is an independent prognostic factor for OS and PFS. ALC-15 ≥ 500 cells/mL is associated with significantly improved clinical outcomes following ASCT in patients with MCL.
Cyclophosphamide Mobilization Does Not Improve Outcome in Patients Transplanted for Multiple Myeloma.
Abstract Patients with multiple myeloma (MM) who undergo high dose therapy (HDT) followed by autologous stem cell transplantation (ASCT) and achieve a complete response (CR) have a superior overall survival (OS) and time to progression (TTP). Thus achieving a CR is an important goal of therapy with ASCT. Cyclophosphamide has significant activity against MM and is often used in high doses prior to ASCT for mobilization of hematopoietic stem cells. We hypothesized that high dose cyclophosphamide (HDC) may further improve CR rates in patients undergoing ASCT. Methods: The Mayo Clinic myeloma transplant database was searched for patients without circulating myeloma cells who had stem cell mobilization with hematopoietic growth factor (HGF) alone or HDC followed by HGF. Relevant demographic, clinical and laboratory characteristics were abstracted. The main outcome studied was the impact of HDC on CR rates and time to progression (TTP) to myeloma. Results: We identified 201 patients without circulating myeloma cells. Of these, 127 were mobilized with HDC and HGF and 74 with HGF alone. The two cohorts were similar with respect to age, gender, isotype, B2M, plasma cell labeling index, cytogenetics, conditioning regimen, disease status at time of transplant with no statistically significant differences between the two cohorts. CR rates were 37.4 and 41.3% (p=0.6115) for patients mobilized with HDC/HGF and HGF respectively. TTP was 19.9 and 17.6 months (p=0.6039) respectively. The median number of collection sessions for patients mobilized with HDC/HGF was 2 (1–10) and those mobilized with HGF was 4 (1–10) (p<0.0001). In a multivariate analysis for TTP, cytogenetics and achieving a CR were the only independent variables (p=0.0012 and p<0.0001). Conclusion: HDC for autologous hematopoietic stem cell collection reduces the number of collections necessary to support HDT/ASCT. However, HDC does not increase CR rates or improve on TTP for patients undergoing ASCT.
Autologous Stem Cell Transplantation for Multiple Myeloma in Patients over 70 Years: A Matched Comparison with Patients under 65 Years.
Abstract Background: High dose therapy with autologous stem cell rescue has been shown to prolong survival in patients with multiple myeloma in randomized controlled trials. However, most of the prospective studies have included younger patients, usually 65 or less. It is important to have a better understanding of the outcome of transplantation in the older patients given the median age of onset of myeloma of 65 years. We retrospectively reviewed our institutions experience with high dose therapy for patients over 70 years. Methods: We identified 35 patients with multiple myeloma, from the transplant database, who were at or over the age of 70 at the time of their high dose therapy. We matched these patients to 70 patients (two matches for each patient), based on stage at transplant (primary refractory, plateau phase, relapse off therapy, or relapse on therapy), Durie Salmon stage, high or low labeling index, conventional cytogenetics (abnormal vs normal), presence or absence of circulating plasma cells at time of transplant, and whether cyclophosphamide was used as part of mobilization in that order of priority. Results: The median age of the two groups were 55.3 (Range 37.3–64.8) and 71.7 (Range 70–75.8) years at the time of transplant. The median time to transplant from diagnosis was similar (6.4 for the older patients compared to 6.9 months for the other, P = NS). Ten of the 35 older patients received reduced dose melphalan (140 mg/2)) compared to 3 patients in the control group; P < 0.01. The median follow up from transplant was 10.1 months for the older patients compared to 18 months for the control group. The overall response rate was similar for the two groups (97.1% for the older patients compared to 95.5 for the control group). Eleven (31%) of the older patients and 17 (24%) of the control patients achieved a CR (P = NS). The post transplant progression free survival estimate at 1 year post transplant was 65.3% for the older patients compared to 66% for the control group (P = 0.3)The two year estimated overall survival from transplant was similar in the two groups; 58% for the older patients compared to 67% for the control group. The overall survival from diagnosis was similar for the two groups (P = 0.6). The median number of days hospitalized was 9 days for the older population compared to 5 days for the control group (P = 0.37). Four patients died within the first one hundred days, one (3%) among the older patient group and 3 (4.3%) in the control group. Conclusions: High dose therapy and autologous stem cell transplantation is feasible in selected patients with multiple myeloma over 70 years. It is likely that these older patients were selected based on their overall performance status, a factor that is difficult to analyze in this retrospective review. Nearly 70% of the elderly patients received full dose melphalan for conditioning (200 mg/m2). The toxicity of transplant as well as the outcome appears to be very similar to the younger patients. Patients with multiple myeloma should not be excluded from high dose therapy solely on the basis of their chronological age.
The Role of Stem Cell Mobilization Regimen on Lymphocyte Collection Yield and Survival after Autologous Hematopoietic Stem Cell Transplantation in Multiple Myeloma.
Abstract We previously have reported that autograft absolute lymphocyte count (A-ALC) is a possible prognostic factor for survival after autologous peripheral blood stem cell transplant (ASCT) for myeloma (MM). Factors affecting A-ALC in MM are unknown. We hypothesize that method of stem cell mobilization, hematopoietic growth factor (HGF) vs. HGF+Cytoxan chemotherapy (C+HGF), directly affects A-ALC collection. 191 consecutive MM patients between 1994 and 2004 were analyzed retrospectively. Patients generally were mobilized with C+HGF prior to 2003. Thereafter, C+HGF was reserved largely for those with ≥4% circulating peripheral blood plasma cells (PC), a negative prognostic indicator. No patients were transplanted in disease relapse or refractory disease. Patients also were matched for age, sex, β2-microglobulin, conventional cytogenetics, LDH, c-reactive protein, number of prior therapies, plasma cell labeling index (PCLI), pre-mobilization ALC, and % bone marrow (BM) PC. The groups HGF (n=80) and C+HGF (n=111) differed with respect to the conditioning regimen (p < 0.0001), and presence of (≥4%) circulating peripheral blood PC (p<0.005). The primary end-point of the study was to assess the correlation between HGF vs C+HGF, and A-ALC. The secondary endpoint was to determine if HGF vs C+HGF affected survival post-ASCT. Patients mobilized with HGF had a higher A-ALC compared to those mobilized with C+HGF [0.764 x 109 lymphocytes/kg (range: 0.146–1.803) vs. 0.212 (range: 0.016–1.26), p<0.0001]. No association was identified between A-ALC and conditioning regimens (p = 0.19) and PC (p = 0.31). Median overall survival (OS) and progression-free survival (PFS) were longer in those mobilized with HGF vs. C+HGF (not reached vs. 48 months, p<0.0150; not reached vs. 21 months, p<0.007, respectively). Multivariate analysis demonstrated that age ≥50 vs age ≤50 (p<0.05) and A-ALC ≥0.5 vs <0.5x109 lymphocytes/kg (p<0.0397) were independent predictors of OS. Factors influencing PFS in the multivariate analysis included circulating PC ≥4% vs <4% (p<0.0157), PCLI ≥ 1% vs PCLI ≤ 1% (p<0.0107), and A-ALC ≥0.5 vs <0.5x109 lymphocytes/kg (p<0.0042). On multivariate analysis, the method of stem cell mobilization and the conditioning regimen did not have a statistically significant effect on either OS or PFS. We hypothesize that the differences in PFS and OS seen between the HGF vs C+HGF mobilization groups are mediated through the A-ALC. These data suggest that mobilization regimens should not only collect CD34+ stem cells, but also be optimized to collect an A-ALC target which may impact on PFS and OS post-ASCT.
Flow Cytometric Detection of Circulating Myeloma Cells Pretransplant in Patients with Multiple Myeloma: A Simple Risk Stratification System.
Abstract Background: The presence of circulating myeloma cells (CMC) detected by flow cytometry at the time of diagnosis of multiple myeloma is associated with a shortened response to therapy and reduced overall survival (OS). We hypothesized that the presence of CMC at the time of stem cell collection prior to high dose therapy (HDT) and autologous stem cell transplantation (ASCT) would identifies a cohort of patients with a high risk of rapid progression. Methods: The Mayo Clinic myeloma transplant database was queried for patients who were mobilized using cyclophosphamide and hematopoietic growth factors. CMC was determined using flow cytometry by gating on a population of CD38 bright and CD45 negative cells. The impact of CMC on OS and time to progression (TTP) and its role in the context of established prognostic parameters was evaluated. Results: Of 246 patients with MM undergoing ASCT, 95 had CMC. Patients with CMC had significantly higher plasma cell labeling index, adverse cytogenetics, B2-M and resistant disease. Complete response (CR) rates post transplant were 32% and 36% for patients with and without CMC (p=0.5034). OS was 33.2 and 58.6 months (p=0.0052) while TTP was 14.1 and 22 months respectively (p=0.0005). Figure Figure On multivariate analysis, CMC remained an independent prognostic factor in a model that included cytogenetics and disease status at time of transplant (p=0.0314). A prognostic system based on the presence or absence of CMC and karyotype abnormalities was developed. Patients with neither, one or both parameters had a median, OS of 55, 48 and 21.5 months respectively (p<0.0001) while TTP was 22, 15.4 and 6.5 months for the same groups (p<0.0001). Conclusion: The presence of CMC at the time of HDT and ASCT is an independent prognostic factor. The combination of CMC and cytogenetics provides a simple yet powerful scoring system that stratifies patients and guides their management.
A Multidisciplinary Quality Initiative for Stem Cell Transplantation in Multiple Myeloma: Outpatient Transplant with Low Therapy Related Mortality
Abstract Introduction: The Bone Marrow Transplant Program at Mayo Clinic (Rochester, Minnesota) developed a multidisciplinary approach (involving physicians, nurses, pharmacists, dietitians, and financial specialists) for outpatient management of patients undergoing stem cell transplantation. This approach uses an electronic ordering system for diagnostic tests and chemotherapy to minimize medical errors. Table. Patient Characteristics (N=716) Characteristic Value Male, no. of patients (%) 426 (59) Age, median (IQR), y 59 (53–65) Creatinine, median (IQR), mg/dL 1.0 (0.9–1.2) b2-Microglobulin, median (IQR), mcg/mL 2.5 (1.9–3.7) Gammopathies, no. of patients (%) Measured by serum immunofixation or immunoelectrophoresis IgA 148 (21) IgG 414 (58) IgM 6 (1) IgD 12 (2) Light chain 83 (12) Biclonal 6 (1) None 47 (7) Measured by urine immunofixation or immunoelectrophoresis k light chain 402 (56) l light chain 226 (32) Biclonal 1 (0) None 79 (11) Not performed (anuric) 8 (1) Status at stem cell transplant, no. of patients (%) Untreated 4 (1) Plateau 436 (61) Primary refractory 113 (16) Relapse after therapy 93 (13) Relapse during therapy 70 (10) Characteristic Value CD34+ cells, median (IQR), ×106/kg Collected, no. 10.0 (7.6–12.6) Infused, no. 4.7 (3.9–6.2) Sessions of apheresis, median (IQR) 3 (2–5) Engraftment, median (IQR), days after transplantation Neutrophils, 0.5×109/L 13 (12–15) Platelets, 50×109/L 16 (14–22) Duration of hospitalization, median (IQR), d 4 (0–10) Abbreviation: IQR, interquartile range. Results: During a 45-month period after implementation of the program (2005-Sept 2007), the day-100 survival rate was 99.5% for low-risk myeloma patients (transplantation during first plateau; n=202) and 97% for high-risk myeloma patients (refractory, relapsing or second or greater plateau; n=71). The overall day-100 survival rate was 99%(270/273). Analysis of hospitalization trends since inception of the program showed that 39% of patients completed the transplant procedure as outpatients. The median duration of hospitalization for all patients was 4 days; age and serum creatinine levels were predictive of the need for and duration of hospitalization Conclusion: Outpatient stem cell transplantation is feasible for patients with multiple myeloma with a therapy mortality of 1%. Nearly 40% of our patients completed the procedure without hospitalization. Age and serum creatinine levels predicted a higher likelihood of hospitalization. Implementation of out patient transplant requires affordable housing in the community since many third party payers do not support hotel costs despite the reduction of hospital days. The hospital physical plant and patient registration process has to support use of designated hospital rooms for purely out patient practice. The transplant team must have process owners to standardize across all disease categories collection protocols, conditioning regimens, infusion SOP’s and post infusion supportive care guidelines for standard antibiotics, narcotics, laboratory work and transfusion thresholds. A care team meeting between physicians, nursing, dietary, pharmacy, business office, data base and appointment coordinators is essential to coordinate all the multidisciplinary efforts. Kaplan-Meier curve shows the percentage of patients remaining in the hospital through time t, stratified on the basis of age greater than or less than or equal to 65 years Kaplan-Meier curve shows the percentage of patients remaining in the hospital through time t, stratified on the basis of age greater than or less than or equal to 65 years Kaplan-Meier curve shows the percentage of patients remaining in the hospital through time t, stratified on the basis of creatinine greater than or equal to or less than 1.5mg/dL Kaplan-Meier curve shows the percentage of patients remaining in the hospital through time t, stratified on the basis of creatinine greater than or equal to or less than 1.5mg/dL
Post Autologous Transplantation Consolidation of Multiple Myeloma with Idiotype-Pulsed Antigen Presenting (Dendritic) Cells (APC8020) Is Associated with Prolonged Survival.
Abstract Introduction: Immunotherapy is most likely to work in a setting of low tumor burden, making vaccine strategies attractive as maintenance therapy post autologous peripheral blood stem cell transplantation (PBSCT) for multiple myeloma (MM). However, it is difficult to ascertain the effects of the vaccines from delayed responses to the transplant. A novel immunotherapeutic, APC8020 (Mylovenge), was studied as consolidation therapy after for MM post PBSCT (Mayo vaccine trial). Mylovenge is prepared from autologous antigen presenting cells, including dendritic cells, partially purified from an unmobilized leukapheresis product by gradient density isolation and then incubated for two days with autologous serum containing M protein obtained pretransplant. We report long term results of the Mayo vaccine trial compared retrospectively to a consecutive cohort of MM patients who underwent autologous stem cell transplant at Mayo Clinic during the same time period. Methods: The Mayo vaccine trial patients had transplants between July of 1998 and May of 2001. Using these cutoff dates we analyzed 151 total MM patients, 27 from the vaccine trial (9 newly diagnosed and 18 relapsed) and 124 from database (DB) (50 newly diagnosed patients and 74 relapsed). The median (range) of follow-up for alive patients in vaccine trial is 6.5 years (2.9 – 8), and in the DB is 7.1 years (6 – 8). Two-sided Fisher’s exact tests and stratified log rank tests (with newly diagnosed or relapsed as the stratum) were used to compare baseline patient characteristics and time to event distributions (overall survival – OS, progression free survival – PFS, and time to progression – TTP) between the two groups. Results: The median (range) of age in vaccine trial and DB was 56 (30–69) and 57 (36–71) years respectively. There were no significant differences in the known prognostic factors including PCLI, B2M, and CRP. The median (95% confidence interval - CI) TTP for the vaccine trial and DB patients was 1.5 years (1.3 – 2.4) and 1.6 years (1.3 – 1.8); stratified log rank p value = 0.46. The median (95% CI) PFS for the vaccine trial and DB patients was 1.5 years (1.3 – 2.4) and 1.5 years (1.1 – 1.8), stratified logrank p value = 0.30. The median (95% CI) OS for the vaccine trial and DB patients was 5.3 years (4.0 -N/A), and 3.4 years (2.7 – 4.6); stratified logrank p value = 0.02. Conclusions: Despite the fact that no difference was seen in TTP or PFS, post-transplant vaccine therapy was associated with prolonged survival. This is similar to what has been reported in other tumor systems including prostate cancer and glioblastoma multiforme. This approach warrants further investigation, including preclinical studies aimed at optimizing the immune response and randomized trials to define the role of vaccine therapy in myeloma. Figure Figure
Comparison of High-Dose Cyclophosphamide and Growth Factor with Growth Factor Alone for Mobilization of Stem Cells for Transplantation in Patients with Multiple Myeloma.
Abstract Introduction: We retrospectively analyzed outcomes of 716 patients with multiple myeloma who were mobilized using cyclophosphamide and growth factor (n=370) or growth factor alone (n=346) before stem cell transplantation. Table. Patient Characteristics (N=716) Variable Cyclophosphamide (n=370) Growth Factor Only (n=346) P Value Abbreviation: IQR, interquartile range. *Or equivalent dosage. Men, No. of patients (%) 224 (61) 202 (58) .50 Age, median (IQR), y 58 (52–64) 60 (53–65) .11 b-2 Microglobulin, median (IQR), mcg/mL 2.7 (1.9–4.0) 2.3 (1.9–3.2) .01 Creatinine, median (IQR), mg/dL 1.1 (0.9–1.3) 1.0 (0.8–1.2) .002 Apheresis, median (IQR) collections, No. 2 (1–3) 4 (3–6) .001 Marrow plasma cells, % 17 (5–34) 5 (1–13) .001 CD34+cells, median (IQR), cells/kg Total collected 10.3x106(7.2x106–14.6x106) 9.9x106(7.6x106–11.9x106) .01 Infused 5.6x106(4.5x106–7.6x106) 4.2x106(3.8x106–5.0x106) <.001 Duration of hospitalization, median (IQR), d 4 (0–10) 4 (0–9) .92 Nonstaphylococcal bacteremia, No. of patients (%) 48 (13) 25 (7) .01 Melphalan dosage, No. of patients (%) .04 200 mg/m2* 337 (91) 298 (86) 140 mg/m2* 33 (9) 48 (14) Exposure before mobilization, No. of patients (%) Melphalan 45 (12) 44 (13) .50 Lenalidomide 14(4) 63(18) .01 Results: Patients receiving cyclophosphamide had higher stem cell yields than the growth factor only group (median number of apheresis sessions needed to achieve stem cell collection goals, 2 vs 4 sessions, respectively [P=.001]). However, patients treated with cyclophosphamide required more time for engraftment of platelets and neutrophils (P<.001 for both). For patients receiving cyclophosphamide, 75% achieved engraftment (defined as a platelet count of 50x109/L) by day 39, whereas 75% of patients not receiving cyclophosphamide achieved engraftment by day 18. Similar results were observed for neutrophil engraftment. These differences did not affect the duration of hospitalization, but patients treated with cyclophosphamide had a higher incidence of posttransplant nonstaphylococcal bacteremia. For cyclophosphamide-mobilized patients, considerably faster platelet engraftment (5 fewer days) resulted if stem cell reinfusion occurred more than 30 days after the first apheresis session. Conclusion: Our data suggested that cyclophosphamide damaged the microenvironment and slowed engraftment. By lengthening the period between the completion of apheresis and stem cell reinfusion, the microenvironment may recover and result in faster engraftment. We suggest that the cyclophosphamide used for mobilization may affect the marrow microenvironment. Cyclophosphamide improves yields but increases bacteremia rates after transplantation. Cyclophosphamide increases time required to collect stem cells and slows engraftment. Figure Figure