Pharmacokinetic and pharmacodynamic investigation of irinotecan hydrochloride in pediatric patients with recurrent or progressive solid tumors.

OBJECTIVE: A multicenter Phase I/II study of Irinotecan hydrochloride (CPT-11; 40-45 mg/m(2)/dose) was conducted for the treatment of refractory pediatric solid tumors. The pharmacokinetics of CPT-11 and its metabolites were characterized using both traditional noncompartmental analysis and population pharmacokinetics using NONMEM VI; pharmacokinetic pharmacodynamic relationships of SN-38 with indices of toxicity were also evaluated. METHOD: 11 patients between 3 and 18 years were enrolled. Pharmacokinetic parameters and consideration of relevant covariates (performance status (PS), BSA, corrected body weight (CBW), exponent of 3/4 on weight, etc.) were evaluated. Relationships between pharmacokinetic parameters of SN-38 and percentage change from baseline in patient biochemical response data were investigated via regression analysis. RESULT: CPT-11 exhibited a mean clearance (CL) of 15.31 +/- 5.95 (l/h) (13.06 +/- 3.58 (l/hr/m(2))) and AUC(0-inf) of 3547.0 +/- 1406.5 (ng x h/ml); the AUC ratio of parent CPT-11 to SN-38 was 5.0%. Based on the population pharmacokinetic analysis, decreasing PS was significantly dependent on reduction in CL of CPT-11 (p < 0.001). The final model for CPT-11 are as follows: CL (l/h) = 1.31 x CBW(0.75) (omegaCL = 21.7%), Vss (l) = 2.66 x CBW (omegaVss = 21.2%), Vc (l) = 1.13 x CBW, inter-compartment CL (l/h) = 0.257 x CBW(0.75). Percentage changes of leucocyte and neutrophil count within a first month treatment were significantly correlated with Cmax of SN-38 (r = 0.78 and r = 0.74) and AUC0-2 of SN-38 (r = 0.73 and r = 0.73). CONCLUSION: Pharmacokinetic parameters were similar to results published in several past reports. An allometric scaling of CBW(0.75) would seem to provide a good index of dosage requirement of CPT-11 in pediatric patients.

A multidisciplinary treatment strategy that includes high-dose chemotherapy for metastatic retinoblastoma without CNS involvement.

The prognosis of patients with metastatic retinoblastoma is poor with conventional chemotherapy and radiation. Since retinoblastoma is highly chemosensitive, dose-escalation of chemotherapeutic agents with stem cell support should be promising. We report our experience with high-dose chemotherapy (HDC) and autologous stem cell transplantation (SCT) in patients with metastatic retinoblastoma. Five patients with metastatic retinoblastoma underwent HDC with autologous SCT following conventional chemotherapy and local radiation therapy. Stem cells (bone marrow in four and peripheral blood stem cells in one) were collected after marrow involvement was cleared. Melphalan was a key drug in all patients, and was administered in combination with other agents such as cisplatin, cyclophosphamide, carboplatin or thiotepa. Three patients are currently alive disease-free at 113, 107 and 38 months, respectively, from the time of SCT. They had no central nervous system (CNS) involvement. The two patients who died of disease had CNS involvement. No long-term sequelae of HDC have been noted. Our treatment strategy using HDC appears to be effective for treating metastatic retinoblastoma without CNS involvement.

Late hemorrhagic cystitis after reduced-intensity hematopoietic stem cell transplantation (RIST).

We reviewed medical records of 256 patients to investigate the frequency and characteristics of hemorrhagic cystitis (HC) associated with reduced-intensity stem cell transplantation (RIST) as opposed to conventional stem cell transplantation (CST); 137 patients underwent CST and 119 RIST. Diagnosis of HC was made based on two or more episodes of sterile, macroscopic hematuria with normal coagulation profiles, without any evidence of renal stones or genitourinary malignancy. Actuarial frequency of HC development in RIST group was 7.6% (9/119), which gave a cumulative annual incidence of 11.7%. In CST group, 13 of 137 patients (9.5%) developed HC, giving an estimated annual incidence of 9.7%. The probability of developing HC was similar between the two groups (P=0.77). The viral etiologies of HC, adenovirus (n=12) and BK virus (n=2), were documented in eight patients after RIST and in six after CST. HC was milder and of a shorter duration, with less blood transfusion requirements, in RIST group than in CST group. A multivariate analysis revealed that HC was associated with antiadenovirus antibody positivity in the recipients, total dose of busulfan, and chronic GVHD. Although HC following RIST is less severe than that following CST, it is still a significant problem.

Induction of graft-versus-autoimmune (GVA) disease effect against refractory psoriasis by complete donor-type chimerism and graft-versus-host disease after allogeneic hematopoietic stem cell transplantation.

A 67-year-old man with AML, who had a 21-year history of psoriasis without remission, received a reduced-intensity transplantation from an HLA-identical sibling. The preparative regimen consisted of busulfan and fludarabine. Graft-versus-host-disease (GVHD) prophylaxis was cyclosporine and methotrexate. Psoriasis was completely resolved on day 18. The subsequent clinical course was uneventful until day 42, when psoriasis recurred at the same sites as before RIST. Peripheral blood examined on day 63 showed mixed chimerism with 54% recipient type. Cyclosporine was rapidly tapered off over the next 2 weeks. On day 90, 100% donor-type chimerism was confirmed. Subsequently, psoriasis improved simultaneously with the occurrence of mucositis and rash as a manifestation of GVHD. Scattered erythematous patches of psoriasis disappeared again by day 105. We initiated 0.5 mg/kg prednisolone on day 119, and resumed cyclosporine on day 133. At 7 months after RIST, he still suffers from chronic GVHD, but his psoriasis remains in remission for the first time in 21 years. The anti-psoriasis effect of the conditioning is mild and transient, while the graft-versus-autoimmunity effect, related to the induction of complete donor-type chimerism and GVHD, is more profound and persisting. A graft-versus-autoimmunity effect lies in the delicate balance between alloimmunity and immunosuppressant used for GVHD prophylaxis/treatment.

Successful treatment of meningoencephalitis caused by methicillin-resistant Staphylococcus aureus with intrathecal vancomycin in an allogeneic peripheral blood stem cell transplant recipient.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common infectious pathogen during stem cell trans-plantation. We report a case of meningoencephalitis with multiple abscess formation caused by MRSA, which occurred in a 4-year-old boy soon after allogeneic peripheral blood stem cell transplantation. We successfully cured the infection with a combination of intravenous and intrathecal vancomycin.

Primary cutaneous aspergillosis caused by Aspergillus ustus following reduced-intensity stem cell transplantation.

A 19-year-old woman with myelodysplastic syndrome underwent reduced-intensity stem cell transplantation [RIST: (cladribine 0.11 mg/kg for 6 days, busulfan 4 mg/kg for 2 days, and rabbit antithymocyte globulin)] from her one HLA-mismatched mother. Prophylaxis against graft-versus-host disease (GVHD) was performed with cyclosporine A (CSA) alone. Severe acute GVHD in the skin, gut, and liver developed concurrently with stable engraftment, and methylprednisolone was administered (1-2 mg/kg per day, then pulse therapy with 1 g/day for 3 days) until day 40 of transplant, when a necrotic lesion of 10 mm in diameter appeared on the right cheek. The initial skin biopsy of the affected area showed a nonspecific inflammatory change. Routine X-ray and computed tomography examinations of the sinuses, chest, and abdomen disclosed no particular abnormalities. Despite intensive antibiotic therapy, the lesion rapidly extended to form an ulcer. A second biopsy specimen obtained from the lesion showed massive septa hyphae, suggesting mold infection. Although we immediately started amphotericin B, she died of multiorgan failure on day 68. Postmortem DNA sequence analysis of the specimen using the polymerase chain reaction identified Aspergillus ustus. Although this is an extremely rare complication after transplantation, this case highlights that we should pay more attention to primary cutaneous aspergillosis in severely immunosuppressed patients.

Suspected delayed immune recovery against cytomegalovirus after reduced-intensity stem cell transplantation using anti-thymocyte globulin.

A reduced-intensity hematopoietic stem cell transplantation (RIST) regimen was developed to induce immunosuppression to facilitate the engraftment of donor cells. However, there have been concerns that the incidence of opportunistic infection may increase after this procedure. To address this problem, we retrospectively analyzed the medical records of 24 RIST recipients who were treated over a recent 16-month period for comparison with 31 recipients of conventional allogeneic transplantation (CST). The RIST regimen consisted of cladribine (0.66 mg/kg), busulfan (8 mg/kg), and rabbit anti-thymocyte globulin (ATG; 5-10 mg/kg). All of the patients received allogeneic peripheral blood stem cells from an HLA-identical or one-locus mismatched related donor. Although the incidence of positive CMV antigenemia was comparable between the two groups (58% vs 68%), RIST patients developed positive antigenemia significantly sooner than did CST patients (P = 0.01) and showed higher initial and maximum antigenemia values (P = 0.026 and P = 0.003, respectively). These findings may suggest that immune recovery against CMV was delayed after our RIST procedure, but this did not directly translate into an increase in clinically significant CMV disease. Early therapeutic intervention with ganciclovir might play a role in preventing the progression of early CMV infection to CMV disease.

Long-term low-dose acyclovir against varicella-zoster virus reactivation after allogeneic hematopoietic stem cell transplantation.

To evaluate the efficacy of long-term administration of acyclovir as prophylaxis against varicella-zoster virus (VZV) reactivation, we analyzed the medical records of 86 consecutive adult patients who obtained engraftment after allogeneic hematopoietic stem cell transplantation from January 1996 to March 2000. We started long-term low-dose (400 mg/day) oral administration of acyclovir in June 1999, and this was continued until the end of immunosuppressive therapy after transplantation. There was no breakthrough reactivation of VZV in patients receiving acyclovir. Five patients who were receiving cyclosporine or prednisolone developed VZV reactivation after discontinuing acyclovir. With this prophylaxis, the cumulative incidence of VZV reactivation at 1 year after transplantation decreased from 33% to 10% (P = 0.025). On multivariate analysis, the use of long-term acyclovir was identified as a significant independent parameter for the development of VZV reactivation. These findings suggest the efficacy of long-term prophylaxis with low-dose acyclovir. Resumption of acyclovir upon restarting immunosuppressive therapy might be important for the further prevention of VZV reactivation. The benefit of long-term low-dose acyclovir should be confirmed prospectively.

Early full donor myeloid chimerism after reduced-intensity stem cell transplantation using a combination of fludarabine and busulfan.

BACKGROUND AND OBJECTIVES: The aim of this study was to evaluate lineage-specific chimerism reconstitution after reduced-intensity allogeneic stem cell transplantation (RIST) using a combination of fludarabine (30 mg/m2 for 6 days) and busulfan (4 mg/kg for 2 days). DESIGN AND METHODS: We prospectively enrolled 8 consecutive patients with hematologic malignancies who were not candidates for conventional transplantation because of either high age or organ dysfunction. Host-donor chimerism was evaluated using polymerase chain reaction-based amplification of a polymorphic short tandem repeat region. RESULTS: All of our patients achieved engraftment within a median of 11 days after transplantation. On day 30, full donor myeloid cell chimerism (>90%) was achieved in 7 patients whereas full donor T-cell chimerism was achieved in only one patient. Thus, in contrast to other reported results, full donor chimerism was achieved earlier in the myeloid lineage than the T-cell lineage. On day 60, however, T-cell chimerism caught up with myeloid chimerism. Two patients developed grade II-IV acute graft-versus-host disease (GVHD) before the detection of full donor T-cell chimerism. INTERPRETATION AND CONCLUSIONS: Our findings suggest that the kinetics of lineage-specific chimerism depend on the agents used in the conditioning regimen, and may provide insight into the chimerism kinetics and pathogenesis of GVHD. Thus, the strategy for controlling immunosuppression after RIST should be modified according to the type of conditioning regimen applied.

Successful application of nonmyeloablative transplantation for paroxysmal nocturnal hemoglobinuria.

OBJECTIVE: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder that manifests as hemolytic anemia, venous thrombosis, and deficient hematopoiesis. Although allogeneic hematopoietic stem cell transplantation is considered the only curative therapeutic measure, transplant-related mortality is not negligible. Several studies supported the use of nonmyeloablative stem cell transplantation (NST) for patients of advanced age or with organ dysfunction. Hence, we used NST in a PNH patient who suffered from acute renal failure due to repeated episodes of hemolysis. MATERIALS AND METHODS: We performed NST using a conditioning regimen consisting of cladribine 0.11 mg/kg x 6, busulfan 4 mg/kg x 2, and rabbit anti-thymocyte globulin 2.5 mg/kg x 2. He received peripheral blood stem cells from his human leukocyte antigen-matched brother. Prophylaxis against graft-vs-host disease was performed with cyclosporine A alone. Chimerism of peripheral blood mononuclear cells was evaluated serially using short tandem repeat analysis and flow cytometry. RESULTS: No meaningful regimen-related toxicities were documented. Donor chimerism of 90 to 100% was achieved on day 14 and thereafter. The patient is doing well, without any recurrence of hemolysis 6 months after transplant. Follow-up chimerism studies confirmed stable and functioning donor-type hematopoiesis. CONCLUSIONS: NST may become a safe and curative approach in patients with PNH. Further studies are needed to establish the role of NST for treatment of PNH.

Possible clinical benefits of the use of peripheral blood stem cells over bone marrow in the allogeneic transplantation setting for the treatment of childhood leukemia.

BACKGROUND: The benefits of allogeneic peripheral blood stem/progenitor cell transplantation (PBSCT) over bone marrow transplantation (BMT), if any, have not been seriously evaluated in a pediatric population. We report here our experience with this procedure and demonstrate rapid engraftment to reduce procedure-related complications and enhanced allogeneic immune reaction to reduce leukemic relapse. METHODS: The feasibility of PBSCT was reviewed retrospectively. Four patients (2 AML and 2 ALL, aged 8-18 years) underwent allogeneic PBSCT for relapsed leukemia after primary allogeneic BMT (n = 2), for active hepatosplenic fungal abscess (n = 1) or for refractory relapse with conventional chemotherapy (n = 1). Four healthy donors (aged 10-49 years) received granulocyte colony-stimulating factor (G-CSF) 10 microg/kg/day by subcutaneous injection for 5 days. An individualized cytoreductive regimen was used before transplantation. RESULTS: No significant toxicities were observed in normal donors on G-CSF treatment or at collection of PBSC. After PBSCT, no significant acute toxicities were observed and the median duration to an absolute granulocyte count of 0.5 x 10(9)/l and a platelet count of 20 x 10(9)/l was 16 and 21 days, respectively. Although none of our patients developed acute graft-versus-host disease (GVHD), two developed chronic GVHD involving the liver and skin. Among those who developed chronic GVHD, one died of recurrent disease and another died of pneumonia 235 days after PBSCT. The two remaining patients have been alive without evidence of disease with follow-ups of 193 and 123 days, respectively. CONCLUSIONS: Allogeneic PBSCT can be a safe procedure in a pediatric population with fewer acute complications, although the potential risk of G-CSF treatment in normal donors should be seriously weighed against the existing risks of marrow aspiration under general anesthesia. The risk of chronic GVHD may need to be balanced against a possible graft-versus-leukemia benefit in patients at higher risk of leukemic relapse.

[A new exanthematous disease in newborn infants caused by exotoxins producing methicillin-resistant Staphylococcus aureus; pathology from viewpoints of local and systemic levels of exotoxin and cytokine].

Neonatal exanthematous diseases induced by toxic shock syndrome toxin-1 (TSST-1)-producing methicillin-resistant Staphyloccocus aureus (MRSA) is one of emerging infectious diseases in Japan. We experienced 36 patients with this disease in National Kagawa Children's Hospital and in 13 patients of them, investigated the role of both the toxin and cytokines in pathogenesis of it. The results are summarized as follows: 1. The TSST-1 level was high in the umbilical inflammatory exudate of cases induced by umbilical infection and in the gastric fluid of cases induced by respiratory infection. The blood TSST-1 level was below the detection limit in most of the exathematous++ cases examined, but it was detected in one of the nine cases induced by respiratory infection and a case secondary to severe MRSA infection (phlegmonous abscess in buttock). 2. Local cytokine levels were examined in the abscess pus obtained from a case of severe MRSA infection and in the gastric fluid from cases induced by respiratory infection. The local levels of TNF [alpha], IL-1 [beta], IL-6 and IL-8 were markedly high, but the local levels of IL-2 and IFN-[gamma] were similar to their blood levels. 3. The severity of hypercytokinemia (IL-1 [beta], IL-2, IL-6, IFN-[gamma]) was proportionate to the severity of exanthematous disease. Accompanied by increased levels of inhibitory factors sTNF-R, IL-1 ra, sIL-2R and IL-10, this hypercytokinemia normalized soon within four or five days. 4. As compared to cases induced by umbilical infection, cases induced by respiratory infection often had higher blood cytokine levels and some of them had cardiorespiratory disorders. Based on the results of this study, we consider that this disease is generally induced by toxemia with a small number of toxins without tissue destructive lesions by MRSA infection and that this is closely related to the course of the disease that shows a tendency to a spontaneous recovery.

Efficacy of the mobilization of peripheral blood stem cells by granulocyte colony-stimulating factor in pediatric donors.

The advantages/disadvantages of the use of peripheral blood stem cells (PBSCs) for allogeneic transplantation still need to be clarified, particularly in children. We compared the kinetics, efficacy, and safety of PBSC mobilization by granulocyte colony-stimulating factor (G-CSF) and collection by apheresis between healthy pediatric and adult donors. A total of 19 pediatric (median age, 6 years) and 25 adult healthy donors (median age, 37 years) were given 10 micro/kg/day of G-CSF for 5 consecutive days for PBSC mobilization, which were harvested by apheresis on days 5 and/or 6. All of the donors tolerated the whole procedures. Serum trough levels of G-CSF determined by ELISA were significantly lower in the 16 pediatric donors evaluated than in adults (n = 16) on days 3 and 4 (P < 0.05). Although the WBC counts on days 4 and 5 were significantly higher in adults than in children (P = 0.006 and 0.004, respectively), the numbers of circulating CD34+ cells/unit of blood were identical. The number of blood CD34+ cells collected per unit of blood processed was identical in both donor populations. We propose that PBSCs could be effectively mobilized and collected in small children so that they could be donors for adult patients.

Comparative evaluation of procedures with a Baxter CS-3000 cell separator for collecting peripheral blood cells from children.

The safety and efficacy of apheresis using a newly developed procedure with a small volume separation container holder (SVSCH, Baxter) for the collection of PBSC from children with cancer were retrospectively compared with our historical experience with other procedures using different equipment and the CS-3000 plus cell separator. The procedures tested included the application of (a) specialized collection protocol 4 using the combination of an SVSCH and a small volume collection chamber (SVCC) (group A: 6 collections in 4 patients), (b) standard lymphocyte collection protocol 3 with GRANULO separation (G) and A-35 collection chambers (group B: 9 collections in 5 patients), and (c) modified collection procedure 1-120 with G and SVCC (group C: 7 collections in 3 patients). Although the retrospective nature of this study and the differences in the cohorts tested prevent a reliable analysis, the percent decrease in the peripheral platelet count after collection tended to be minimum in group A (11% +/- 5% versus 23% +/- 4% [B] or 17% +/- 4% [C]). Moreover, the largest number of CD34+ cells was collected in group A (8.7 +/- 9.4 x 10(5)/100 ml processed blood) compared with groups B (5.5 +/- 7.5 x 10(5)/100 ml processed blood) and C (4.0 +/- 2.8 x 10(5)/100 ml processed blood). These data suggest that a procedure incorporating SVSCH can be safely and effectively applied to small children and enables the selective collection of PBSC with less contamination by platelets, which is useful for subsequent cell processing.

Endogenous interleukin-8 (IL-8) surge in granulocyte colony-stimulating factor-induced peripheral blood stem cell mobilization.

The relationship between stem cell mobilization with granulocyte colony-stimulating factor (G-CSF) and the endogenous production of interleukin-8 (IL-8), macrophage inflammatory protein-1alpha (MIP-1alpha), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) was studied in normal donors for allogeneic peripheral blood stem cell (PBSC) transplantation. G-CSF was administered to 20 normal donors at a dose of 10 microg/kg/d for 5 days with aphereses on days 5 and 6 of G-CSF treatment. Cytokine serum levels were measured using an enzyme-linked immunosorbent assay (ELISA) before and during G-CSF treatment. Before treatment, the average level of IL-8 was 7.1 pg/mL, increasing to 207.0 pg/mL on day 5 and 189.1 pg/mL on day 6. Serum IL-8 levels correlated CD34(+) cell numbers (P =.0151 and P =.0005 on days 5 and 6, respectively) and colony-forming unit-granulocyte-macrophage (CFU-GM) numbers (P =.0019 and P =.0010 on days 5 and 6, respectively). Furthermore, preapheresis serum IL-8 levels correlated with the yield of CD34(+) cells (P =.0027). In contrast, before treatment, the average levels of MIP-1alpha, TNF-alpha, and IFN-gamma were 70.1, 4.03, and 3.84 pg/mL, respectively, and no significant changes in the levels of these cytokines were observed during G-CSF treatment. These studies suggest that IL-8 production may be critical to G-CSF-induced stem cell mobilization, although the underlying mechanism could not be clarified.

Clinically applicable bulk isolation of blood CD34+ cells for autografting in children.

CD34+ cells were purified in bulk from apheresis-collected cells of children with cancer using monoclonal antibody (MoAb) and magnetic beads (Baxter ISOLEX system). To improve the purity of the final product for possibly better tumor cell purging and to make the manufacturer's original procedure more cost-effective, we incubated the cells for 30 min with l-phenylalanine methylester hydrochloride (PME) to reduce the cell number by removing contaminating granulocytes and monocytes in the initial step before incubation with MoAb. Our modification prevented nonspecific interactions between MoAb and magnetic beads, and thereby saved expensive materials for purification. A total of 40 purifications were performed with samples containing a mean of 3.1 x 10(9) blood cells mobilized from 15 children by chemotherapy plus granulocyte colony-stimulating factor (G-CSF). The entire purification procedure, from the end of apheresis to storage, was completed within 5h. After incubation with PME and double-layered (40/60%) Percoll separation, the number of CD34+ cells was reduced to 48+/-29%, which suggests the possibility that half of the CD34+ cells in the inoculum were nonclonogenic in the hematopoietic progenitor assay. PME/Percoll-treated cells were then subjected to a final isolation procedure with MoAb according to the manufacturer's suggestions, and 52+/-42% and 32+/-22%, respectively, of the CFU-GM and CD34+ cells present in the initial bag inoculums were recovered. The recovery rates were, respectively, 54% and 67%, when the calculation was limited to the isolation procedure with MNoAb. The purity of isolated CD34+ cells and the plating efficiency in methylcellulose culture were, respectively, 77+/-24% and 33+/-13%. Fourteen children were subsequently autografted with purified CD34+ cells after marrow ablative chemotherapy. The median number of days to achieve an ANC of 0.5 x 10(9)/l was 12 and that to achieve a platelet count of 50 x 10(9)/l was 22.5, which were comparable to those in our historical group of 55 patients who underwent transplant with unmanipulated blood cells (13 and 16 days). These results suggest that our modified purification procedure with PME is useful for the initial reduction of cell numbers to save costly materials, and that cells isolated by this procedure can be directly used in clinical transplantation procedures.

Intra-apheresis recruitment of blood progenitor cells in children.

BACKGROUND: Determination of the optimal duration of apheresis requires a careful examination of blood progenitor cell (BPC) kinetics during apheresis. Intra-apheresis recruitment of BPCs should be evaluated. STUDY DESIGN AND METHODS: Twenty-six apheresis procedures were performed in 13 children with various malignant disorders (ages, 10 months to 17 years; median, 7 years) to collect BPCs for autologous transplant, using a blood cell separator with 2 to 5.2 blood volumes processed. The subjects were divided into three groups according to age: below 1 year (n = 4), 2 to 10 years (n = 5), and 11 to 20 years (n = 4). BPCs were mobilized by a combination of chemotherapy and granulocyte-colony-stimulating factor (G-CSF; 2-7.5 micrograms/kg/day intravenous drip). The levels of circulating CD34+ cells and colony-forming units-granulocyte-macrophage (CFU-GM) were monitored to examine intra-apheresis recruitment. For every 50 mL per kg or 2 L of processed blood, 5-mL blood samples were collected via a central line. RESULTS: In the first apheresis procedure, more CD34+ cells were mobilized by the procedure itself in the infant group than in the older groups, and the number of cells decreased with the subject's age. When the same analysis was made during the second apheresis procedure, performed 1 day later, the levels of both CD34+ cells and CFU-GM had decreased to below the preapheresis values in all of the populations. Cell yields in the second apheresis procedure were significantly lower than those in the first. CONCLUSION: Although several factors prevent a reliable analysis, the data suggest that the intra-apheresis recruitment of BPCs may be age-specific; the continuous and prolonged supply of cells from the bone marrow to peripheral blood that occurs during apheresis is more predominant in infants, which leads to the collection of proportionately more BPCs in younger children than in their older counterparts.

New consecutive high-dose chemotherapy modality with fractionated blood stem cell support in the treatment of high-risk pediatric solid tumors: a feasibility study.

For the treatment of childhood solid tumors, we performed a pilot feasibility study of consecutive high-dose therapies, in which each course was followed by transplantation with granulocyte colony-stimulating factor-mobilized peripheral blood cells which had been separated into CD34-positive and -negative fractions by an Isolex system (Baxter). Positive selection of CD34+ cells has been associated with inevitable cell loss. To overcome this loss, CD34+ cells that had migrated into the negative fraction were saved and used for the first transplant, which was followed by a second transplant after a 3- to 5-month interval. In this phase I feasibility study, the results in six children were evaluated for safety and engraftment. Multi-drug cytoreductive regimens using ranimustine (MCNU), melphalan, thiotepa, carboplatin, cyclophosphamide or VP-16 were comparable between the two transplant procedures in terms of their intensity. The number of CD34+ cells in the 'CD34(+) fraction' was 3.31 x 10(6)/kg (0.63-4.3 x 10(6)/kg), while this number in the 'CD34(-) fraction' could not be evaluated correctly due their scarcity (<0.1%). The median numbers of infused MNC and CFU-GM were, respectively, 4.2 x 10(6)/kg and 1.75 x 10(5)/kg in the CD34(+) fraction, and 4.8 x 10(8)/kg and 3.35 x 10(5)/kg in the CD34(-) fraction. The number of days required to achieve an ANC >0.5 x 10(9)/l and a platelet count >20 x 10(9)/l and >50 x 10(9)/l were, respectively, 14.5, 15.0 and 19.5 in the first transplant with CD34- cells, and 13.5, 18.0 and 25.0 in the second transplant with CD34+ cells, with no essential difference between the two treatments. Although the small number of patients, the variation in clinical status and treatment, and the short follow-up invalidate any evaluation of the therapeutic benefit of this strategy, the encouraging results support the feasibility of this strategy, which enables an escalation of dose intensity with an improved cost/benefit ratio.