Bendamustine, etoposide and dexamethasone to mobilize peripheral blood hematopoietic stem cells for autologous transplantation in patients with multiple myeloma.

Chemotherapeutic agents without cross-resistance to prior therapies may enhance PBSC collection and improve patient outcomes by exacting a more potent direct antitumor effect before autologous stem cell transplant. Bendamustine has broad clinical activity in transplantable lymphoid malignancies, but concern remains over the potential adverse impact of this combined alkylator-nucleoside analog on stem cell mobilization. We performed a prospective, nonrandomized phase II study including 34 patients with multiple myeloma (MM) (n=34; International Staging System (ISS) stages I (35%), II (29%) and III (24%); not scored (13%)) to evaluate bendamustine's efficacy and safety as a stem cell mobilizing agent. Patients received bendamustine (120 mg/m2 IV days 1, 2), etoposide (200 mg/m2 IV days 1-3) and dexamethasone (40 mg PO days 1- 4) (bendamustine, etoposide and dexamethasone (BED)) followed by filgrastim (10 µg/kg/day SC; through collection). All patients (100%) successfully yielded stem cells (median of 21.60 × 106/kg of body weight; range 9.24-55.5 × 106/kg), and 88% required a single apheresis. Six nonhematologic serious adverse events were observed in 6 patients including: neutropenic fever (1, grade 3), bone pain (1, grade 3) and renal insufficiency (1, grade 1). In conclusion, BED safely and effectively mobilizes hematopoietic stem cells.

A randomized study of melphalan 200 mg/m(2) vs 280 mg/m(2) as a preparative regimen for patients with multiple myeloma undergoing auto-SCT.

We aimed to examine whether doses of melphalan higher than 200 mg/m(2) improve response rates when used as conditioning before autologous transplant (ASCT) in multiple myeloma (MM) patients. Patients with MM, n=131, were randomized to 200 mg/m(2) (mel200) vs 280 mg/m(2) (mel280) using amifostine pretreatment. The primary end point was the proportion of patients achieving near complete response (⩾nCR). No treatment-related deaths occurred in this study. Responses following ASCT were for mel200 vs mel280, respectively, ⩾nCR 22 vs 39%, P=0.03, ⩾PR 57 vs 74%, P=0.04. The hazard of mortality was not statistically significantly different between groups (mel200 vs mel280; hazard ratio (HR)=1.15 (95% confidence interval (CI), 0.62-2.13, P=0.66)) nor was the rate of progression/mortality (HR=0.81 (0.52-1.27, P=0.36)). The estimated PFS at 1 and 3 years were 83 and 46%, respectively, for mel200 and 78 and 54%, respectively, for mel280. Amifostine and mel280 were well tolerated, with no grade 4 regimen-related toxicities and only one grade 3 mucositis (none with mel200) and three grade 3 gastrointestinal (GI) toxicities (two in mel200). Hospitalization rates were more frequent in the mel280 group (59 vs 43%, P=0.08). Mel280 resulted in a higher major response rate (CR+nCR) and should be evaluated in larger studies.

Maintenance rituximab after autologous stem cell transplantation in patients with mantle cell lymphoma.

BACKGROUND: High-dose therapy and autologous stem cell transplantation (ASCT) improves outcomes for patients with mantle cell lymphoma (MCL), but relapse ultimately occurs in most patients. Recently presented interim results from a phase III prospective trial suggest maintenance rituximab (MR) after ASCT for MCL improves progression-free survival (PFS). The maturation of these data and any benefit of MR on overall survival (OS) remain to be defined. PATIENTS AND METHODS: In this retrospective study, we examined a cohort of consecutive patients with MCL that underwent ASCT for MCL at our center and evaluated their outcomes according to whether they received MR after ASCT (n = 50) or did not (n = 107). MR was treated as a time-dependent covariate to account for variation in timing of its initiation. RESULTS: MR was associated with an improved PFS [hazard ratio (HR) 0.44; confidence interval (CI) (0.24-0.80), P = 0.007] and overall survival (OS; HR 0.46; CI 0.23-0.93, P = 0.03) following a multivariate adjustment for confounding factors with a median follow-up of ∼5 years. Grade 4 neutropenia was increased (34% versus 18%, P = 0.04) in the MR group, but no effect on the rate of mortality unrelated to relapse was observed. CONCLUSIONS: These data support that MR after ASCT for MCL confers a benefit in PFS and additionally suggest it may improve OS. General application of this strategy will require confirmation of benefit in prospective randomized trials.

Utilization of stored autologous PBSCs to support second autologous transplantation in multiple myeloma patients in the era of novel agent therapy.

Outcomes in multiple myeloma (MM) have improved significantly with novel agent therapy and autologous stem cell transplantation (ASCT). ASCTs are typically planned as either tandem or a single transplant with additional stored PBSCs available for a second salvage transplant. To accommodate these strategies, many centers routinely collect and store adequate PBSCs for two ASCTs. We analyzed the cost associated with this practice by determining the expenses of PBSC collection, cryopreservation and storage, and the ultimate use of additional cryopreserved PBSCs in patients who had undergone at least one ASCT. There were 889 MM patients transplanted between 1993 and 2011 at our center. Most (N=726) had residual PBSCs in storage after their first ASCT (ASCT1). Only 135 patients underwent a second ASCT within a median of 14 months after ASCT1. The percentage of patients receiving a second ASCT declined over time. The resources required to collect and store unused PBSCs added up to 336 extra patient days of apheresis and 41 587 extra patient months of cryopreservation, translating into an average extra cost per patient of US$4981.12. A reconsideration of conventional PBSC collection and storage practices would save significant cost for the majority of MM patients who never undergo a second ASCT.

Immune escape from NY-ESO-1-specific T-cell therapy via loss of heterozygosity in the MHC.

Adoptive immunotherapy of tumors with T cells specific for the cancer-testis antigen NY-ESO-1 has shown great promise in preclinical models and in early stage clinical trials. Tumor persistence or recurrence after NY-ESO-1-specific therapy occurs, however, and the mechanisms of recurrence remain poorly defined. In a murine xenograft model of NY-ESO-1(+) multiple myeloma, we observed tumor recurrence after adoptive transfer of CD8(+) T cells genetically redirected to the prototypic NY-ESO-1157-165 peptide presented by HLA-A*02:01. Analysis of the myeloma cells that had escaped from T-cell control revealed intact expression of NY-ESO-1 and B2M, but selective, complete loss of HLA-A*02:01 expression from the cell surface. Loss of heterozygosity (LOH) in the major histocompatibility complex (MHC) involving the HLA-A locus was identified in the tumor cells, and further analysis revealed selective loss of the allele encoding HLA-A*02:01. Although LOH involving the MHC has not been described in myeloma patients with persistent or recurrent disease after immune therapies such as allogeneic hematopoietic cell transplantation (HCT), it has been described in patients with acute myelogenous leukemia who relapsed after allogeneic HCT. These results suggest that MHC loss should be evaluated in patients with myeloma and other cancers who relapse after adoptive NY-ESO-1-specific T-cell therapy.

A prospective study of lenalidomide monotherapy for relapse after Allo-SCT for multiple myeloma.

Allo-SCT can result in long-term remission in patients with multiple myeloma (MM), although its overall role in disease management remains controversial. We evaluated lenalidomide monotherapy response and tolerability among 18 patients with MM who progressed or relapsed after Allo-SCT, who were enrolled a median of 12 months (range 3-104) following transplant. Treatment duration of lenalidomide was 8 months (range 1-57). Ten patients required dose reductions from 25 to 5-20 mg at a median of three cycles (range 1-12): eight for neutropenia, one for thrombocytopenia and one for myalgias and weakness. Serious adverse events (N=5) included H1N1 influenza (2), bacterial pneumonia (2) and fever, myalgia and hypoxia. Two patients died at 3 and 5 months of gastrointestinal or hepatic GVHD occurring within 1 month of dosing. Responses included complete response (CR) (5), very good partial response (2), partial response (PR) (3), minimal response (1) and stable disease (2) for an overall response rate (≥ PR) of 56%. Ten patients discontinued therapy for progressive disease (PD) at a median of 8.5 (1-43) months. Six patients died from PD. Five patients remained on therapy at 39 months (range 14-57), with four in CR. Lenalidomide for relapse of MM after Allo-SCT can result in extended disease control (>12 months) in 50% of patients.

Safety and preliminary efficacy of plerixafor (Mozobil) in combination with chemotherapy and G-CSF: an open-label, multicenter, exploratory trial in patients with multiple myeloma and non-Hodgkin's lymphoma undergoing stem cell mobilization.

Plerixafor, a novel CXCR4 inhibitor, is effective in mobilizing PBSCs particularly when used in conjunction with G-CSF. In four cohorts, this pilot study explored the safety of plerixafor mobilization when incorporated into a conventional stem cell mobilization regimen of chemotherapy and G-CSF. Forty (26 multiple myeloma and 14 non-Hodgkin's lymphoma) patients were treated with plerixafor. Plerixafor was well tolerated and its addition to a chemo-mobilization regimen resulted in an increase in the peripheral blood CD34+ cells. The mean rate of increase in the peripheral blood CD34+ cells was 2.8 cells/microl/h pre- and 13.3 cells/microl/h post-plerixafor administration. Engraftment parameters were acceptable after myeloblative chemotherapy, with the median day for neutrophil and plt engraftment being day 11 (range 8-20 days) and day 13 (range 7-77 days), respectively. The data obtained from the analysis of the cohorts suggest that plerixafor can safely be added to chemotherapy-based mobilization regimens and may accelerate the rate of increase in CD34+ cells on the second day of apheresis. Further studies are warranted to evaluate the effect of plerixafor in combination with chemomobilization on stem cell mobilization and collection on the first and subsequent days of apheresis, and its impact on resource utilization.

Role of autologous and allogeneic stem cell transplantation in myeloma.

The treatment of multiple myeloma (MM), a largely incurable B-cell hematologic malignancy, is changing dramatically. Autologous stem cell transplantation (SCT) and the approval of two new classes of drugs, immunomodulators and proteosome inhibitors, have resulted in improved response rates and increased overall survivals. Thalidomide, bortezomib and lenalidomide have been combined with corticosteroids, alkylators and anthracyclines in front-line MM treatment. Phase 2 and preliminary phase 3 studies have reported very high response rates and complete response rates formerly seen only with SCT. When patients with MM who have received these new drugs then proceed to transplant, major response rates are further increased. Owing to limited follow-up, it is unclear whether these higher response rates translate into increased survival. Despite these improvements, the disease remains incurable for all but a small fraction of patients. Allogeneic SCT is potentially curative, due in part to a graft-versus-myeloma effect but is limited by mortality. Mortality can be reduced through the use of lower intensity conditioning regimens but this comes at a cost of higher rates of disease progression and relapse. Strategies to improve outcomes of allogeneic transplants include more intensive, yet non-myeloablative conditioning regimens, tandem transplants, peripheral blood cells, graft engineering, post-transplant maintenance and targeted conditioning therapies.

The impact of histologic grade on the outcome of high-dose therapy and autologous stem cell transplantation for follicular lymphoma.

The impact of the follicular lymphoma (FL) histologic grade on outcomes after high-dose therapy (HDT) and autologous stem cell transplantation (ASCT) is unknown. We evaluated 219 consecutive patients with grades 1-3 FL who underwent HDT and ASCT at our center. Overall survival (OS), progression-free survival (PFS), relapse and non-relapse mortality (NRM) was estimated for each grade after controlling for other predictive factors. The number of patients with grades 1, 2 and 3 FL was 106 (48%), 75 (34%) and 38 (17%), respectively. Five-year outcome estimates for the entire cohort included 60% OS, 39% PFS and 46% relapse (median follow-up=7.8 years). PFS and relapse were nearly identical among patients with grade 3 FL versus grades 1-2 FL after adjusting for other contributing factors (hazard ratio (HR)=0.90, P=0.68; HR=1.07, P=0.80, respectively). The hazard for mortality (HR=0.70, P=0.23) and NRM (HR=0.33, P=0.07) was non-significantly lower among patients with grade 3 FL compared to patients with grades 1-2 disease. Factors associated with inferior PFS included elevated lactate dehydrogenase (HR=1.52, P=0.03), chemoresistance (HR=1.82, P=0.02), > or =2 prior therapies (HR=1.8, P=0.03) and prior radiation (HR=1.99, P=0.003). These data suggest that the histologic grade of FL does not impact PFS or relapse following HDT and ASCT.

The current status of reduced-intensity allogeneic hematopoietic stem cell transplantation for multiple myeloma.

Of all the treatment modalities employed to control multiple myeloma, only allogeneic hematopoietic stem cell transplantation is potentially curative, due in large part to a graft-versus-myeloma (GVM) effect. Whereas patients who receive either allogeneic or autologous stem cell transplants for multiple myeloma have similar 3-5-year survival, only allograft recipients appear to enjoy long-term disease-free survival. High transplant-related mortality (TRM) associated with allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative modality. This high mortality has been the major impetus for exploration of reduced intensity conditioning (RIC) regimens designed to allow engraftment of allogeneic stem cells. With follow-up now extending to 7 years, it is clear that when compared to myeloablative transplants, RIC allografts are associated with lower TRM; however, reduced mortality comes at a cost of higher rates of disease progression and relapse. Strategies designed to improve the therapeutic index of allografts include the use of more intensive, yet still non-myeloablative conditioning regimens, tandem autologous plus RIC allografts, peripheral blood cells rather than bone marrow, graft engineering to improve the GVM activity while reducing graft-versus-host disease, post-transplant maintenance and targeted conditioning therapies such as bone-seeking radioisotopes.

Reliability and validity of a patient self-administered daily questionnaire to assess impact of oral mucositis (OM) on pain and daily functioning in patients undergoing autologous hematopoietic stem cell transplantation (HSCT).

Oral mucositis (OM) is a frequent complication of myeloablative therapy and HSCT. We evaluated the feasibility, reliability, and validity of a new patient self-reported daily questionnaire on OM and its impact on daily functions. This OM Daily Questionnaire (OMDQ), containing 10 items, was developed for use in palifermin clinical trials. In a phase 3 study, 212 patients received palifermin or placebo for three consecutive days before conditioning and three consecutive days after HSCT. Compliance rates were consistently >80% for most patients. Mouth and throat soreness (MTS) and MTS-Activity Limitations (MTS-AL) (swallowing, drinking, eating, talking, and sleeping) scores on consecutive days were highly correlated (days 7,8 = 0.70-0.86; test-retest reliability). Correlations among items measuring the same construct ranged between 0.5 and 0.8 (internal consistency reliability). The WHO Oral Toxicity scale was the clinical comparator to assess the criterion, discriminative, and evaluative validities of MTS-related questions. Most correlation coefficients between the WHO and MTS ranged between 0.45 and 0.55. Patients with more severe WHO OM grades had higher MTS mean scores. Changes in MTS scores were similar, but patients detected changes 1-3 days earlier than clinicians. In conclusion, the OMDQ is a feasible, reliable, valid, and responsive patient-reported measure of OM severity.

A new conditioning regimen involving total marrow irradiation, busulfan and cyclophosphamide followed by autologous PBSCT in patients with advanced multiple myeloma.

The overall survival of patients with advanced multiple myeloma (MM) undergoing high-dose chemotherapy and autologous stem cell transplantation (SCT) depends mainly on the quality of response. Thus, to improve the response rate, a new intensified high-dose chemoradiotherapy was evaluated in a phase I/II study. After induction chemotherapy, 89 patients (median age 51 years, range 32-60 years) with MM stage II/III received a conditioning regimen with total marrow irradiation (9 Gy), busulfan (12 mg/kg) and cyclophosphamide (120 mg/kg) followed by SCT. Regimen-related toxicity according to WHO criteria and response rates defined by EBMT/IBMTR were analyzed. The main toxicity was mucositis grade III/IV in 76%, and fever grade >I in 75% of patients. Three patients developed reversible veno-occlusive disease. Transplant-related mortality was 2%. Among patients with de novo and pretreated MM, a CR rate of 48 and 41%, respectively, was documented. With a median follow-up of 45 months, the actuarial median durations of event-free survival (EFS) and overall survival (OS) after transplant were 29 and 61 months for the whole group, 36 and 85 months for patients with de novo MM, respectively. Thus, administration of this intensified conditioning regimen was associated with tolerable toxicity, a high response rate and long EFS and OS.

Incidence, risk factors, and mortality from pneumonia developing late after hematopoietic stem cell transplantation.

The incidence, etiology, outcome, and risk factors for developing pneumonia late after hematopoietic stem cell transplantation (SCT) were investigated in 1359 patients transplanted in Seattle. A total of 341 patients (25% of the cohort) developed at least one pneumonic episode. No microbial or tissue diagnosis (ie clinical pneumonia) was established in 197 patients (58% of first pneumonia cases). Among the remaining 144 patients, established etiologies included 33 viral (10%), 31 bacterial (9%), 25 idiopathic pneumonia syndrome (IPS, 7%), 20 multiple organisms (6%), 19 fungal (6%), and 16 Pneumocystis carinii pneumonia (PCP) (5%). The overall cumulative incidence of first pneumonia at 4 years after discharge home was 31%. The cumulative incidences of pneumonia according to donor type at 1 and 4 years after discharge home were 13 and 18% (autologous/syngeneic), 22 and 34% (HLA-matched related), and 26 and 39% (mismatched related/unrelated), respectively. Multivariate analysis of factors associated with development of late pneumonia after allografting were increasing patient age (RR 0.5 for <20 years, 1.2 for >40 years, P=0.009), donor HLA-mismatch (RR 1.6 for unrelated/mismatched related, P=0.01), and chronic graft-versus-host disease (GVHD; RR 1.5, P=0.007). Our data suggest that extension of PCP prophylaxis may be beneficial in high-risk autograft recipients. Further study of long-term anti-infective prophylaxis based on patient risk factors after SCT appear warranted.

A randomized phase III clinical trial of autologous blood stem cell transplantation comparing cryopreservation using dimethylsulfoxide vs dimethylsulfoxide with hydroxyethylstarch.

Hematopoietic stem cells intended for autologous transplantation are usually cryopreserved in solutions containing 10% dimethylsulfoxide (DMSO, v/v) or 5% DMSO in combination with 6% hydroxyethylstarch (HES, w/v). We performed a single-blinded, randomized study comparing these cryoprotectant solutions for patients undergoing autologous peripheral blood stem cell (PBSC) transplantation. A total of 294 patients were evaluable; 148 received cells frozen with 10% DMSO and 146 received cells frozen in 5% DMSO/6% HES. Patients who received cells frozen with the combination cryoprotectant recovered their white blood cell count >or=1.0 x 10(9)/l at a median of 10 days, one day faster than those who received PBSC frozen with DMSO alone (P=0.04). Time to achieve neutrophil counts of >or=0.5 x 10(9) and >or=1.0 x 10(9)/l were similarly faster for the recipients of the cells frozen in the combination solution. This effect was more pronounced for patients who received quantities of CD34+ cells higher than the median for the population. Median time to discontinuation of antibiotic use was also one day faster for the recipients of cells cryopreserved with DMSO/HES (P=0.04). In contrast, median times to recovery of platelet count >or=20 x 10(9)/l were equivalent for each group (10 days; P=0.99) and the median numbers of red cell and platelet transfusions did not differ.

Allogeneic hematopoietic cell transplantation for multiple myeloma.

At the present time, allogeneic hematopoetic stem cell transplantation (AHSCT) is the only proven treatment for multiple myeloma (MM) that is potentially curative. This conclusion is based on observations of patients who have undergone AHSCT and are living disease-free for 5-15 years. While patients who receive either allogeneic or autologous stem cell transplants for MM have similar 3-5 year survival, only allograft recipients appear to enjoy long-term disease free survival. This is most likely due to an allogeneic graft-versus-myeloma effect, demonstrated most dramatically by complete responses observed after the simple infusion of donor lymphocytes for patients who have relapsed after a prior allograft. The very high transplant related mortality associated with standard allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative treatment modality. Complications are age-related and thus standard AHSCT is offered only to patients under age 55; further limiting the utility of this treatment. The challenge for clinical investigators will be to reduce the incidence of post-transplant complications for patients receiving AHSCT for MM. These strategies include the use of non-ablative conditioning regimens, the use of peripheral blood stem cells rather than bone marrow, graft engineering and targeted conditioning therapies such as bone-seeking radioisotopes. In one such approach, tandem autologous/non-ablative allogeneic transplants have been shown to result in relatively low mortality, high complete response rates and 1-year survivals of 81%. Further follow-up and randomized trials will help to define the utility of this strategy.

Decreased transfusion requirements for patients receiving nonmyeloablative compared with conventional peripheral blood stem cell transplants from HLA-identical siblings.

Red blood cell (RBC) and platelet transfusion requirements in patients given nonmyeloablative versus conventional peripheral blood stem cell (PBSC) transplants from HLA-matched siblings were compared. Between December 1997 and March 2000, 40 patients, aged 21 to 67 years (median 51), with hematologic malignancies underwent nonmyeloablative allografts after either 2 Gy total body irradiation alone (n = 30) or 2 Gy total body irradiation preceded by fludarabine 30 mg/m(2)/d on days -4, -3, and -2 (n = 10). All received postgrafting mycophenolate mofetil and cyclosporine. Controls included 67 concurrent patients, aged 23 to 66 years (median, 46 years), given conventional PBSC transplants following high-dose conditioning and postgrafting methotrexate and cyclosporine. Among patients given nonmyeloablative transplants, 23% required platelet transfusions compared with 100% among patients given conventional grafts (P <.0001). Further, the number of platelet units given to nonmyeloablative recipients was reduced, with a median of 0 (range, 0 to 214) compared with a median of 24 (range, 4 to 358) after conventional transplantation (P <.0001). Sixty-three percent of nonmyeloablative recipients required RBC transfusions compared with 96% of those with conventional grafts (P =.0001). The number of RBC units transfused was also reduced, with a median of 2 (range, 0 to 50) compared with 6 (range, 0 to 34) after conventional transplantation (P =.0001). High transfusion requirements before transplantation and donor-recipient ABO incompatibility increased transfusion requirements in both patient groups, though neither significantly influenced the outcome of the analysis. Neither patient age, splenomegaly at transplantation, development of graft-versus-host disease, nor posttransplantation cytomegalovirus antigenemia or cytomegalovirus disease had statistically significant influences on posttransplantation transfusions.

Trafficking of CD34+ cells into the peripheral circulation during collection of peripheral blood stem cells by apheresis.

The number of CD34+ cells collected during apheresis is related to the volume of blood processed. In large-volume apheresis (LVL) procedure, more cells can be collected than were originally present in the peripheral blood at the start of the collection procedure. We prospectively studied the levels of CD34+ cells in the blood and apheresis product during LVL procedures for 21 patients with acute myelogenous leukemia or multiple myeloma. These patients experienced a slow decline in blood CD34+ cell concentrations during the apheresis procedure. No patient demonstrated a sustained rise in CD34+ cell counts as a result of the procedure. The number of CD34+ cells collected exceeded the number calculated to be in the peripheral blood at the start of the procedure by an average of 3.0-fold. The efficiency of collection for CD34+ cells averaged 92.6% and did not vary with speed of blood processing, diagnosis, or mobilization regimen. The calculated release of CD34+ cells from other reservoirs into the peripheral blood averaged 3.71 x 10(6)/min (range, 0.36-13.7 x 10(6)/min), and correlated (r = 0.82) with the concentration of these cells in the peripheral blood at the start of the procedure. These data show that the apheresis procedure used in this study does not affect the release of CD34+ cells in a cytokine-treated patient. LVL will result in collection of larger quantities of CD34+ cells than procedures involving processing of smaller volumes of blood, but the number of cells collected is limited by the rate of release of these cells into the peripheral circulation where they are accessible for collection.

CD34 cell dose in granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell grafts affects engraftment kinetics and development of extensive chronic graft-versus-host disease after human leukocyte antigen-identical sibling transplantation.

A retrospective analysis of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cell (G-PBMC) products harvested from healthy donors indicates significant variability in both the absolute number and relative proportion of CD34, CD3, and CD14 cells obtained. This report examined whether variations in the cellular composition of G-PBMC products correlated with clinical outcomes after myeloablative allogeneic transplantation. The numbers of CD34, CD3, and CD14 cells infused into 181 human leukocyte antigen (HLA)-identical sibling recipients were analyzed with respect to tempo of engraftment, acute graft-versus-host-disease (GVHD), clinical extensive chronic GVHD, overall survival, and disease relapse. Neither acute GVHD, overall survival, nor disease relapse was statistically significantly associated with CD34, CD3, or CD14 cell doses or the CD14 to CD3 ratio. CD3 and CD14 cell doses and CD14 to CD3 ratios did not correlate with the tempo of neutrophil and platelet engraftment. However, increasing CD34 cell numbers were significantly associated with accelerated neutrophil (P =.03) and platelet (P =.01) engraftment. Higher doses of CD34 cells (> 8.0 x 10(6)/kg) were also associated with a significantly increased hazard of clinical extensive chronic GVHD (HR = 2.3, 95% confidence interval [CI] 1.4-3.7, P =.001), but neither CD3 nor CD14 doses were statistically significantly associated with chronic GVHD. It was concluded that CD34 cell dose in G-PBMC grafts appears to affect both the engraftment kinetics and the development of clinical extensive chronic GVHD in HLA-identical sibling recipients but without a demonstrable impact on survival, relapse, and acute GVHD. Given the morbidity associated with extensive chronic GVHD, efforts to further accelerate engraftment in HLA-matched sibling transplants by increasing CD34 cell number in G-PBMC products may be counterproductive.