Activating KIR Haplotype Influences Clinical Outcome Following HLA-Matched Sibling Hematopoietic Stem Cell Transplantation.

Natural killer cells are thought to influence the outcome of hematopoietic stem cell transplant (HSCT), impacting on relapse, overall survival, graft versus host disease and the control of infection, in part through the complex interplay between the large and genetically diverse killer immunoglobulin-like receptor (KIR) family and their ligands. This study examined the relationship between KIR gene content and clinical outcomes including the control of opportunistic infections such as cytomegalovirus in the setting of human leucocyte antigen (HLA)-matched sibling HSCT in an Australian cohort. The presence of the KIR B haplotype which contain more activating receptors in the donor, in particular centromeric B haplotype genes (Cen-B), was associated with improved overall survival of patients with acute myeloid leukemia (AML) undergoing sibling HSCT and receiving myeloablative conditioning. Donor Cen-B haplotype was also associated with reduced acute graft versus host disease grades II-IV whereas donor telomeric-B haplotype was associated with decreased incidence of CMV reactivation. In contrast, we were not able to demonstrate a reduced rate of relapse when the donor had KIR Cen-B, however relapse with a donor Cen-A haplotype was a competing risk factor to poor overall survival. Here we show that the presence of donor activating KIR led to improved outcome for the patient, potentially through reduced relapse rates and decreased incidence of acute GvHD translating to improved overall survival. This article is protected by copyright. All rights reserved.

Immunogenicity and safety of a two-dose live attenuated varicella vaccine given to adults following autologous hematopoietic stem cell transplantation.

BACKGROUND: Immunogenicity and safety of varicella vaccine (Varilrix(™) [Oka-RIT]; GlaxoSmithKline Vaccines) in adults who had undergone autologous hematopoietic stem cell transplantation (HSCT) were assessed (September 2003 to September 2007; NCT00792623). METHODS: Two Oka-RIT doses were given at 4.5 and 6.5 months post transplantation. Humoral immune responses were assessed using an immunofluorescence assay (anti-varicella zoster virus [VZV] antibody; cutoff 1:4) after each vaccine dose. Solicited local (8 day) and general (43 day), unsolicited (until day 43) adverse events (AEs) after each vaccine dose and serious adverse events (SAEs) (until 17.5 months post dose 2) were recorded. RESULTS: Of 45 patients, 19 were included in the according to protocol cohort for immunogenicity; 15 patients had pre- and post-vaccination serum samples positive for anti-VZV antibodies. Vaccine responses (anti-VZV antibody titer ≥1:4 in seronegative patients, and ≥4-fold increase in anti-VZV antibody titer in seropositive patients) were elicited by only 2 patients 2 months post dose 1, and by a single patient 1.5 months post dose 2. Although no major safety signals were detected, any and Grade 3 solicited AEs that were causally related to vaccination were reported by 44.8% and 10.3% patients, respectively. During the 43-day follow-up period, 3 patients developed varicella-like rash (1 vaccine-type VZV). Beyond 43 days, herpes zoster was reported in 2 patients and wild-type varicella infection in 2 patients (1 was breakthrough infection). Four non-fatal SAEs were reported by patients and considered causally unrelated to vaccination. CONCLUSION: Oka-RIT was poorly immunogenic but safe when given to adults up to 6 months post autologous HSCT, and alternative strategies are required to prevent VZV-associated complications in these populations.

High-dose cytarabine (24 g/m2) in combination with idarubicin (HiDAC-3) results in high first-cycle response with limited gastrointestinal toxicity in adult acute myeloid leukaemia.

BACKGROUND/AIM: Although induction chemotherapy comprising high-dose cytarabine (HiDAC) in combination with idarubicin and etoposide or 'ICE' for adult acute myeloid leukaemia (AML) produces a complete remission rate of nearly 80%, gastrointestinal toxicity is significant. Omission of etoposide may produce similar clinical outcomes with potentially less gastrointestinal toxicity. METHODS: Fifty-three consecutive patients aged 15-60 with newly diagnosed AML, receiving high-dose cytarabine induction at the Alfred Hospital, Melbourne, were retrospectively analysed. Regimens included HiDAC-3 (idarubicin 12 mg/m(2) day 1-3, cytarabine 3 gm/m(2) bd day 1,3,5,7) or ICE (idarubicin 9 mg/m(2) day 1-3, cytarabine 3 g/m(2) bd day 1,3,5,7, etoposide 75 mg/m(2) day 1-7). Toxicity was assessed using Common Terminology Criteria for Adverse Events version 4.03. RESULTS: Thirty-one patients received HIDAC-3 and 22 patients received ICE induction. HiDAC-3 was better tolerated than ICE in terms of lower frequency of grade 3-4 nausea (0% vs 41%; P < 0.01), grade 3-4 diarrhoea (26% vs 55%; P = 0.05), lower rates of radiologically evident enterocolitis (6% vs 32%; P = 0.03) and less cumulative days of total parenteral nutrition use (1.2 vs 7.3 days; P < 0.01). Times to haematological recovery were similar between the two regimens. Thirty-day mortality was 0% for HiDAC-3 and 9% for ICE. Eighty-four per cent of HiDAC-3-treated patients achieved complete remission after the first cycle of therapy, compared with 77% with ICE. No differences in survival were evident between the two regimens. CONCLUSIONS: HiDAC-3 is a clinically effective induction regimen for adult AML, producing a high rate of first-cycle complete remission with less treatment-related gastrointestinal toxicity than ICE.

Long-term follow-up of a pilot study using a chemotherapy-alone protocol for killer Ig-like receptor-ligand-mismatched haploidentical haematopoietic SCT.

Advanced haematological malignancies are incurable without allogeneic haematopoietic SCT (HSCT). Many patients do not have a human leukocyte Ag (HLA)-matched donor; hence, haploidentical HSCT has been explored for some 20 years. Previous poor outcomes have improved recently with modifications, including the use of killer Ig-like receptor (KIR)-ligand-mismatched donors and highly T-cell-depleted megadose CD34+ stem cell infusions. Haploidentical HSCT was undertaken in 10 patients with heavily pretreated and advanced myeloid malignancies. Patient/donor pairs were KIR-ligand mismatched (GVL direction). Conditioning regimen was ATG, melphalan, fludarabine and thiotepa. G-CSF-mobilized PBSCs were CD34+ cell selected. No post transplant immunosuppression was given. Two patients died early; all others had sustained engraftment. Natural killer cell recovery, often to supranormal levels, occurred early, whereas CD4+ T-cell recovery was delayed. Acute GVHD occurred in three of eight (30%) patients, and chronic GVHD occurred in three of six (50%) evaluable patients. No infections with Candida or Aspergillus developed in seven patients receiving caspofungin prophylaxis. Three of 10 (30%) patients were alive and disease free at 10.1, 6 and 5.4 years post transplant (Karnovsky scores of 100%). In this heavily pretreated cohort with very advanced myeloid malignancies, KIR-ligand-mismatched haploidentical HSCT cured a significant proportion of patients.

Patients with chronic myeloid leukemia who maintain a complete molecular response after stopping imatinib treatment have evidence of persistent leukemia by DNA PCR.

Around 40-50% of patients with chronic myeloid leukemia (CML) who achieve a stable complete molecular response (CMR; undetectable breakpoint cluster region-Abelson leukemia gene human homolog 1 (BCR-ABL1) mRNA) on imatinib can stop therapy and remain in CMR, at least for several years. This raises the possibility that imatinib therapy may not need to be continued indefinitely in some CML patients. Two possible explanations for this observation are (1) CML has been eradicated or (2) residual leukemic cells fail to proliferate despite the absence of ongoing kinase inhibition. We used a highly sensitive patient-specific nested quantitative PCR to look for evidence of genomic BCR-ABL1 DNA in patients who sustained CMR after stopping imatinib therapy. Seven of eight patients who sustained CMR off therapy had BCR-ABL1 DNA detected at least once after stopping imatinib, but none has relapsed (follow-up 12-41 months). BCR-ABL1 DNA levels increased in all of the 10 patients who lost CMR soon after imatinib cessation, whereas serial testing of patients in sustained CMR showed a stable level of BCR-ABL1 DNA. This more sensitive assay for BCR-ABL1 provides evidence that even patients who maintain a CMR after stopping imatinib may harbor residual leukemia. A search for intrinsic or extrinsic (for example, immunological) causes for this drug-free leukemic suppression is now indicated.

Reduced-intensity conditioned allogeneic haematopoietic stem cell transplantation results in durable disease-free and overall survival in patients with poor prognosis myeloid and lymphoid malignancies: eighty-month follow-up.

The long-term outcome of patients with haematological malignancies treated with reduced-intensity conditioned allogeneic peripheral blood stem cell transplantation is not known. We report the outcome of 79 patients with poor-risk myeloid and lymphoid malignancies transplanted with reduced-intensity conditioning (RIC) regimens. The diagnoses include AML/myelodysplastic syndrome (n=43), non Hodgkin's lymphoma (n=30), Hodgkin's lymphoma (n=3), ALL (n=2) and CML (n=1). For the entire cohort, the disease-free survival (DFS) and OS were 61.2 and 35.7%, respectively. Twenty patients relapsed, 18 within the first three years, and 14 patients succumbed to progressive disease. Overall, 31 patients died from transplant-related complications within the first three years. Day 100 non-relapse mortality correlated with a higher total nucleated cell dose in the graft (odds ratio: 3.9). For those in CR at 3 years, the DFS and OS were 84.2 and 81.1%, respectively. Furthermore, of 43 patients with active disease at the time of transplantation, 16 remained in CR after 3 years. The majority of the long-term survivors were functioning independently. One patient died from a second malignancy. No post-transplant lymphoproliferative disorder was seen. In conclusion, durable disease control was achieved after RIC allogeneic stem cell transplantation for patients with advanced myeloid and lymphoid malignancies.

The role of stem cell mobilization regimen on lymphocyte collection yield in patients with multiple myeloma.

BACKGROUND: The lymphocyte dose (LY-DO) infused during an autograft influences absolute lymphocyte (ALC) recovery and survival following autologous stem cell transplantation (ASCT) in multiple myeloma (MM) patients. Factors influencing lymphocyte yield (LY-C) during leukapheresis have been poorly studied. METHODS: Factors that could influence survival, LY-C and CD34(+) cell yield were analyzed in 122 MM patients. Three mobilization regimens were used, granulocyte-colony-stimulating factor (G-CSF) alone (n=13), cyclophosphamide 1-2 g/m(2) plus G-CSF (LD-CY, n=62) and cyclophosphamide 3-4 g/m(2) and G-CSF (ID-CY, n=47). RESULTS: Using multivariate analysis, age, LY-C, ALC on day 30 (ALC-30) and International Staging System stage significantly influenced overall (OS) and progression-free survival (PFS) following ASCT. PFS (56 versus 29 months, P=0.05) and OS (72 versus 49 months; P=0.07) were longer in the LY-C>or=0.12x10(9)/kg group than the LY-C<0.12x10(9)/kg group. LY-C also influenced ALC on day 15 (ALC-15). Mobilization regimen, lymphocytes on the day of leukapheresis, prior radiotherapy and number of leukaphereses significantly influenced LY-C. Significantly higher LY-C was obtained with G-CSF alone compared with the LD-CY and ID-CY groups. CD34(+) count on the day of leukapheresis, prior chemotherapy with prednisone, cyclophosphamide, adriamycin and BCNU or melphalan, and stem cell mobilization regimen significantly influenced CD34(+) cell yield. DISCUSSION: LY-C influenced ALC-15 and survival following ASCT. Factors that influenced CD34(+) cell yield and LY-C during leukapheresis were different. Mobilization should be tailored to maximize the LY-C and CD34(+) cell yield.

Intermediate-dose CY and G-CSF more efficiently mobilize adequate numbers of PBSC for tandem autologous PBSC transplantation compared with low-dose CY in patients with multiple myeloma.

BACKGROUND: Autologous PBSC transplantation is the standard care for patients with multiple myeloma. The most common regimen used to mobilize PBSC consists of CY and G-CSF. METHODS: We retrospectively analyzed the efficacy and toxicity of two regimens of CY for PBSC mobilization: low-dose CY (1-2 g/m(2), LD-CY, n=61) plus G-CSF, and intermediate-dose CY (3-4 g/m(2), ID-CY, n=26) plus G-CSF. RESULTS: In the LD-CY group, 5.17 (0.23-17.3)x10(6) CD34(+) cells/kg, and in the ID-CY group 7.71 (0.08-26.4)x10(6) CD34(+) cells/kg (P=0.018), were collected. Although >/=2x10(6)/kg CD34(+) cells were collected in 89% of the LD-CY group and 92% of the ID-CY group, this was achieved after a single leukapheresis in 54% of the LD-CY group and 92% of the ID-CY group (P=0.0001). Patients who are to have tandem autologous PBSC transplants require >/=4x10(6)/kg CD34(+) cells. This was achieved in only 65% patients in the LD-CY group but 88% in the ID-CY group (P=0.05). Among patients who had not had prior melphalan and/or >12 months of prior treatment, 74% in the LD-CY group and 100% in ID-CY group mobilized >/=4x10(6)/kg CD34(+) cells. Febrile neutropenia was more frequent in the ID-CY group (38% vs. 13%). DISCUSSION: In conclusion, compared with LD-CY, patients receiving ID-CY were more likely to collect a total CD34(+) cell number adequate for tandem autologous PBSC transplantation. The increased toxicity was manageable and considered acceptable.

A randomized comparison of empiric or pre-emptive antibiotic therapy after hematopoietic stem cell transplantation.

We performed a randomized comparison of pre-emptive and empiric antibiotic therapy for adult patients undergoing allogeneic or autologous stem cell transplantation. One hundred and fifty-three patients were randomized to receive cefepime either pre-emptively on the day that neutropenia (ANC<1.0 x 10(9) cells/l) developed irrespective of the presence of fever, or at onset of fever and neutropenia (empiric). Although there was no difference between the two arms in the proportion of patients developing fever or in the median number of days of fever, the time to onset of fever was a mean of 1 day longer in each patient on the pre-emptive arm (log rank P<0.001). The number of patients with bloodstream infections was significantly reduced in those receiving pre-emptive therapy (16/75) compared to the empiric arm (31/76) (P<0.01) but this did not translate into an appreciable clinical benefit as measured by days of hospitalization, time to engraftment, use of additional antimicrobial agents or mortality at 30 days. This study does not support the use of pre-emptive intravenous antibiotic therapy in adult stem cell transplant recipients.

14thInternational HLA and Immunogenetics Workshop: report on hematopoietic cell transplantation.

Deciphering the role of human leukocyte antigen (HLA), killer immunoglobulin like receptor, and immune response genes in a model as complex as unrelated donor hematopoietic cell transplantation is a challenge. The allelic diversity of these genes is shaped by the race and ethnicity of transplant donors and recipients. Coupled with the genetic polymorphism is the complexity of clinical phenotypes of transplant populations: donor and recipient demographic characteristics and the regimens used by transplant physicians to prepare patients for transplantation and to prevent and treat graft-vs-host disease (GVHD). Furthermore, GVHD is itself a complex disease shaped by both genes and 'environment'. How does one begin to deconstruct the genetic barrier to understand risk factors important to transplant outcome? To begin with, population-based studies, particularly retrospective ones, benefit from adequate sample sizes to measure genetic effects. The more homogeneous the population for variables that influence clinical endpoints, the higher the likelihood that a real genetic effect can be uncovered. Even so, the feasibility of studies can be hampered if genotype and clinical data are not both complete and precise. For studies of HLA, diversity of alleles and antigens contributed by ethnically different transplant populations is an asset, because not only can a broader range of HLA mismatches be studied but they provide the opportunity for side-by-side analyses that may yield clues as to why transplant outcomes differ between populations.

Caspofungin as salvage monotherapy for invasive aspergillosis in patients with haematological malignancies or following allogeneic stem cell transplantation: efficacy and concomitant cyclosporin A.

Caspofungin (CAS) has shown efficacy as salvage monotherapy for invasive aspergillosis (IA) in two open label non-comparative trials. The association between hepatotoxicity and concomitant use of CAS and cyclosporin A (CsA) has not been fully elucidated. We report results on CAS efficacy in the first cohort from outside Europe and USA and the interaction between CAS and CsA. We retrospectively reviewed the charts of all patients with haematological malignancies or postallogeneic haematopoietic stem cell transplant (HSCT) who received >/=1 dose of CAS as salvage monotherapy for IA as part of the Australian Special Access Scheme (4/2001-8/2002). Outcomes were assessed at the end of CAS therapy. Favourable response (FR) was defined as >50% clinical and radiological improvement. Risk factors for elevation of liver transaminases (LTs) were examined using multivariate models. 54 patients were included in the analysis with 47 neutropenic at study entry. Proven or probable IA occurred in 11 and refractory IA in 28. An FR occurred in 26 (48.1%) and predictors for a poor response to CAS were allogeneic HSCT, graft vs. host disease and treatment with CAS for <14 days. Concomitant CAS and CsA for >7 days was an independent risk factor for laboratory hepatoxicity. The CAS efficacy results from the Australian cohort confirm those of previous studies. Close monitoring of LTs is necessary on concomitant CAS and CsA but clinically relevant hepatotoxicity is rare.

Kappa immunoglobulin light chain polymorphisms and survival after allogeneic transplantation for B-cell malignancies: a potential graft-vs-leukaemia target.

In the human leucocyte antigen (HLA)-matched haematopoietic stem cell transplantation (HSCT) setting, minor histocompatibility antigen (mHA) disparities between recipient and donor can lead to graft-vs-host disease (GVHD) or graft rejection. Graft-vs-leukaemia (GVL) effect is a beneficial T-cell-mediated immune response that can also occur following HLA-matched HSCT. mHAs with tissue expression restricted to cells of the haematopoietic system are particularly relevant as immunotherapeutic targets for destroying malignant cells without inducing GVHD. Therefore, it is important to identify further haematopoietic-restricted polymorphic mHAs, which may have the potential to be used clinically for adoptive immunotherapy. Polymorphic mismatching of minor antigens, such as the B-cell-specific protein, the kappa immunoglobulin light chain (kappa) may play a role in the incidence of GVL and therefore the survival of transplant recipients following transplantation for B-cell malignancies. Polymorphisms in the constant region of the immunoglobulin kappa polypeptide chain have been defined involving single amino acid changes at positions 153 and 191. In this study, 51 HLA-matched B-cell malignancy transplant pairs were kappa typed by polymerase chain reaction and restriction enzyme digestion to investigate the association between kappa allotype disparity and outcome after transplantation. Kappa allotype disparity between transplant pairs may be associated with an increased survival compared with pairs not mismatched for kappa, as kappa mismatched recipients had a higher percentage of complete remissions and a decreased level of relapse in comparison with the nonmismatched recipients. HLA peptide prediction software was used to determine which HLA types were the best binders for kappa peptides. It was observed that patients with tissue types predicted to bind the kappa Km(1,2) peptides had better survival outcomes and no relapse compared with those with tissue types not predicted to bind the kappa Km(1,2) peptides. This study may contribute to the assessment of the clinical role of kappa with regard to the outcome of allogeneic transplantation for B-cell malignancies.

Pamidronate reduces bone loss after allogeneic stem cell transplantation.

BACKGROUND: Rapid bone loss occurs from the proximal femur after allogeneic stem cell transplantation (alloSCT). OBJECTIVE: The objective of the study was to evaluate effects of high-dose pamidronate therapy on bone loss (BMD) after alloSCT. DESIGN: This was a randomized, multicenter, open-label, 12-month prospective study of iv pamidronate (90 mg/month) beginning before conditioning vs. no pamidronate. All 116 patients also received calcitriol (0.25 microg/d) and calcium (1000 mg/d), which were continued for another year. MAIN OUTCOME MEASURES: Primary objectives were to compare changes in BMD 12 months after alloSCT at the femoral neck, lumbar spine, and total hip between the treatment arms and assess influences of glucocorticoid and cyclosporin therapy on these changes. RESULTS: Pamidronate reduced bone loss at the spine, femoral neck, and total hip by 5.6, 7.7, and 4.9% (all P < or = 0.003), respectively, at 12 months. However, BMD of the femoral neck and total hip was still 2.8 and 3.5% lower than baseline, respectively (P < 0.05) with pamidronate. Only differences at the total hip remained significant between the two groups at 24 months. Benefits were restricted to patients receiving an average daily prednisolone dose greater than 10 mg and cyclosporin therapy for more than 5 months within the first 6 months of alloSCT. CONCLUSIONS: Pamidronate markedly reduced but did not completely prevent postallogeneic bone marrow transplantation bone loss. BMD benefits were greatest in patients on higher doses of immunosuppressive therapy, but most were lost 12 months after stopping pamidronate. Studies of more potent bisphosphonates or anabolic therapy with PTH after alloSCT are warranted with the aim of durable maintenance of bone mass.

A randomized, open-label, multicenter comparative study of the efficacy and safety of piperacillin-tazobactam and cefepime for the empirical treatment of febrile neutropenic episodes in patients with hematologic malignancies.

BACKGROUND: The empirical treatment of febrile, neutropenic patients with cancer requires antibacterial regimens active against both gram-positive and gram-negative pathogens. This study was performed to demonstrate the noninferiority of monotherapy with piperacillin-tazobactam, compared with cefepime. METHODS: We conducted a randomized-controlled, open-label, multicenter clinical trial among high-risk patients from 34 university-affiliated tertiary care medical centers in the United States, Canada, and Australia who were undergoing treatment for leukemia or hematopoietic stem cell transplantation and were hospitalized for empirical treatment of febrile neutropenic episodes. Patients received piperacillin-tazobactam (4.5 g every 6 h) or cefepime (2 g every 8 h) intravenously. The primary outcome was success (defined by defervescence without treatment modification) at 72 h of treatment, end of treatment, and test of cure in the modified intent-to-treat analysis. Secondary outcomes included time to defervescence, microbiological efficacy, the additional use of glycopeptide antibiotics, emergence of resistant bacteria, and safety. RESULTS: For 528 subjects (265 received piperacillin-tazobactam and 263 received cefepime), success rates were 57.7% and 48.3%, respectively (P = .04) at the 72-h time point, 39.6% and 31.6% (P = .06) at end of treatment, and 26.8% and 20.5% (P = .11) at the test-of-cure visit. The analyses demonstrated noninferiority for piperacillin-tazobactam at all time points (P< or = .0001). Treatment with piperacillin-tazobactam was independently associated with treatment success in multivariate analysis (odds ratio, 1.65; 95% confidence interval, 1.04-2.64; P = .035). Both regimens were well tolerated. CONCLUSIONS: This study demonstrates the noninferiority and safety of piperacillin-tazobactam monotherapy, compared with cefepime, for the empirical treatment of high-risk febrile neutropenic patients with cancer.

CD34+-derived CD11c+ + + BDCA-1+ + CD123+ + DC: expansion of a phenotypically undescribed myeloid DC1 population for use in adoptive immunotherapy.

BACKGROUND: DC are commonly defined as HLA-DR+/Lin- cells that can be CD11c+ + + CD123+/ -, termed DC1/myeloid DC that induce a Th1 response, or CD11c- CD123+ + +, termed DC2/lymphoid DC that induce a Th2 response. However, significant heterogeneity within DC preparations is apparent and supports the existence of several distinct DC subpopulations. This study aimed to expand and characterize CD34+ DC for use in immunotherapy. METHODS: CD34+ cells were seeded at 1 x 10(5)/mL and expanded for 14 days in RPMI + 10% autologous plasma supplemented with GM-CSF, IL-4, Flt-3L and SCF. Maturation was induced with TNF-alpha and PGE2 for 2 days. DC were analyzed morphologically, phenotypically with a panel of MAb to lineage and DC markers, and functionally in MLR, T-cell assays and T-cell cytokine secretion by ELISA. RESULTS: Significant cellular expansion was observed: 60+/-5 x 10(6) DC from 1 x 10(6) CD34+ cells (n=28). Phenotypically DC were characterized as HLA-DR+ +, CD11c+ + +, CD80+ +, CD83+, CD86+ +, CD123+ +, CD15+ +, CD33+ +, BDCA-1+ +, CD4+ and Lin-. DC displayed potent allostimulatory capacity and efficient presentation of KLH and tetanus toxin. DC-primed T cells secreted IFN-gamma (Th1); however, no detectable IL-4 (Th2) was noted. DISCUSSION: We present features of CD34+ DC that have not been previously described. The CD34+ DC generated represent a population of myeloid DC functioning as DC1 but phenotypically expressing markers characteristic of both DC1 and DC2. This novel DC population is capable of inducing naive T-cell responses and can be expanded to clinically useful numbers. CD34+-derived DC represent attractive candidates for use in adoptive T-cell immunotherapy.

Successful mobilization of peripheral blood stem cells using recombinant human stem cell factor in heavily pretreated patients who have failed a previous attempt with a granulocyte colony-stimulating factor-based regimen.

To assess the efficacy of recombinant human stem cell factor (rHuSCF), 48 patients who had failed to mobilize >2.0 x 10(6) CD34+ cells/kg with granulocyte colony-stimulating factor (G-CSF) (10 microg/kg twice daily) with, or without, concomitant chemotherapy (G-CSF-based regimen), were remobilized with the addition of rHuSCF (20 microg/kg/day). In all, 18/48 (38%) achieved a total of >2.0 x 10(6) CD34+ cells/kg with the second rHuSCF-based mobilisation alone and 29/48 (60%) achieved a cumulative total of >2.0 x 10(6) CD34+ cells/kg following remobilization. Inclusion of chemotherapy in the mobilization regimen resulted in a higher yield of CD34+ cells/kg for both the initial G-CSF-based and subsequent rHuSCF-based regimens (0.90 vs 0.54, P < 0.01 and 2.36 vs 1.34, P < 0.01, respectively). The total peripheral blood stem cells PBSC collected from the G-CSF-based regimen, performance status, baseline platelet count and albumin were significantly associated with successful remobilization. Patients with multiple myeloma were also more likely to successfully remobilize. There was no threshold of total collected from the failed G-CSF-based regimen below which successful remobilization with the rHuSCF-based regimen was not possible. We therefore propose a predictive model [PBSC expected = 0.6+(G-CSF-based total collection)+2 (rHuSCF-based day 1 collection)] to calculate the cumulative total of PBSC expected following a maximum of five leukaphereses. This algorithm may permit the early identification of patients who are unlikely to achieve sufficient PBSC for transplantation and allow physicians to direct the resources involved in PBSC collection in a more appropriate and economical manner.