Comparison of the approaches to non-febrile neutropenia developing in children with acute lymphoblastic leukemia

The objectives of this study was to investigate of the influences of high-dose (20 mg/kg/day) methyl prednisolone (HDMP) and granulocyte colony stimulating factor (G-CSF) in shortening the duration of chemotherapy-induced neutropenia encountered in children with ALL receiving maintenance therapy. Sixty-four non-febrile neutropenic attacks developed in 29 patients with ALL receiving St Jude XIII maintenance protocol were evaluated retrospectively. The patients were clinically followed up without drugs for shortening the duration of neutropenia in 21 (32.8%) attacs, while HDMP and G-CSF were administered in 26 (40.6%) and 17 (26.6%) attacks, respectively. After the detection of neutropenia, restoration of neutrophil counts at 2nd or 4th days to the levels that allow resuming the chemotherapy were considered as success. While second day and overall success rates in patients administered HDMP and G-CSF were significantly higher than the patients who were observed clinically. Both second day and overall neutrophil counts were significantly higher in patients administered G-CSF than the other groups. Methyl prednisolone and G-CSF treatments were well-tolerated by the patients. The cost-per neutropenic attack was significantly higher in G-CSF group than of the HDMP group. Especially in patients experiencing frequent neutropenic attacks and hence interruptions of the therapy, one of the myelopoiesis induction therapies can be used to shorten the duration of neutropenia. For this indication short-course HDMP therapy can be considered as an alternative to G-CSF in this patients due to its relatively low cost, amenability to outpatient administration, and well-tolerability by children.     

Levels of recombinant human granulocyte colony-stimulating factor in serum are inversely correlated with circulating neutrophil counts.

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) is effective in countering chemotherapy-induced neutropenia. However, serum rhG-CSF levels cannot be maintained throughout the course of rhG-CSF therapy. The drop in serum rhG-CSF levels may vary with the duration of rhG-CSF administration or with the circulating neutrophil counts. We investigated the relationship between serum G-CSF levels and circulating neutrophil counts and the pharmacokinetics of rhG-CSF for patients with lung cancer who had been treated with myelosuppressive chemotherapy and then with subcutaneous rhG-CSF (lenograstim, 2 micrograms per kg of body weight per day). Twelve patients were randomly assigned to four groups with different rhG-CSF therapy schedules. Serum G-CSF levels were measured by an enzyme immunoassay method. Serum G-CSF levels during the rhG-CSF therapy greatly exceeded endogenous G-CSF levels and were mainly due to the presence of exogenous rhG-CSF rather than increased levels of endogenous G-CSF. Despite the duration of rhG-CSF administration, serum G-CSF levels during rhG-CSF therapy were inversely correlated with circulating neutrophil counts (r2 = 0.73, P < 0.0001). The value for the area under the concentration-time curve of rhG-CSF on the day of neutrophilia was lower than that on the day of neutropenia (P < 0.05). Our results suggest that the fall in serum G-CSF levels during rhG-CSF therapy may result from increased clearance and/or decreased absorption of rhG-CSF, two processes related to circulating neutrophil counts.     

Chronic neutropenia. A new canine model induced by human granulocyte colony-stimulating factor.

Normal dogs were treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) at 10 micrograms/kg/day for 30 d, which caused an initial neutrophilia, followed by a prolonged period of chronic neutropenia. A control dog treated with recombinant canine G-CSF (rcG-CSF) showed persistent neutrophilia over 3 mo. Serum from dogs during neutropenia contained an antibody to rhG-CSF, which neutralized the stimulatory effects of both rhG-CSF and rcG-CSF on dog marrow neutrophilic progenitor cell growth and on NFS-60 cell proliferation. 4 mo after discontinuation of rhG-CSF, the dogs' neutrophil counts returned to the normal range. Rechallenge with the rhG-CSF re-induced severe neutropenia in 1 wk. Neutropenia was transferred by plasma infusion from a neutropenic dog to a previously normal dog. These data suggest that human rhG-CSF immunizes normal dogs and thereby induces neutralization of endogenous canine G-CSF and neutropenia. This model system should allow more precise definition of the in vivo role of G-CSF.     

Systemic production of human granulocyte colony-stimulating factor in nonhuman primates by transplantation of genetically modified myoblasts

Clinical use of human granulocyte-colony stimulating factor (hG-CSF) to treat various diseases involving neutropenia has been previously shown to (1) successfully increase circulating neutrophils, (2) reduce condition-related infections, and (3) cause few side effects in patients. To alleviate the symptoms of neutropenia, the patient must receive frequent injections of recombinant hG-CSF. Permanent ways to deliver stable levels of the molecule to the patient are being investigated. Among them, the transplantation of hG-CSF-secreting cells has been proposed and performed successfully in rodents, using fibroblast cell lines and primary muscle cells. We thus investigated whether similar results could be obtained by intramuscular myoblast transplantation in a large animal model. When 1-3 x 10(8) myoblasts were injected into three Macaca mulatta, hG-CSF was detected at high levels (300-900 pg/ml), which in turn led to a four- to fivefold increase in circulating neutrophils. However, both the concentrations of hG-CSF and neutrophil levels were found to decrease over time. Nonetheless, neutrophils were found at higher levels from the fourth week until the end the experiment (up to 29 weeks) in G-CSF monkeys compared with control animals. These results show that transplantation of hG-CSF-secreting myoblasts may indeed be a therapeutic option for the treatment of neutropenic patients.     

Persistent, therapeutically relevant levels of human granulocyte colony-stimulating factor in mice after systemic delivery of adeno-associated virus vectors.

Adeno-associated virus (AAV) vectors have been shown to preferentially transduce hepatocytes after systemic administration in adult mice and to provide long-term expression of introduced genes. One application of this technology would be for the production of granulocyte colony-stimulating factor (G-CSF), which increases mature neutrophil numbers in humans and in animals, and has therapeutic effects in disorders featuring chronic neutropenia, including cyclic, severe congenital, and idiopathic neutropenia, and glycogen storage disease type Ib. We have treated mice by tail vein injection of AAV vectors encoding human G-CSF, and have detected high G-CSF levels and marked elevation of neutrophil counts for at least 5 months. A therapeutically relevant amount of G-CSF production was obtained when the liver-specific mouse albumin promoter-enhancer was used to drive G-CSF expression. In mice receiving higher amounts of vector, plasma levels of human G-CSF gradually increased over 3 weeks to high concentrations, whereas for lower amounts human G-CSF remained at initial, low levels. The previously observed effect of gamma irradiation, to increase AAV transduction rates, was diminished when large amounts of vector were used. Absolute neutrophil counts increased 10- to 50-fold for the period of observation to levels that would be therapeutic in the treatment of cyclic neutropenia. In conclusion, gene therapy with AAV vectors synthesizing G-CSF shows promise for the treatment of disorders featuring neutropenia.     

Probable vancomycin-induced neutropenia

OBJECTIVE: To report a case of vancomycin-induced neutropenia and provide a review of the literature. CASE SUMMARY: A 64-year-old white man was treated with intravenous vancomycin 1.5 g/day for finger osteomyelitis. He developed neutropenia after 21 days of vancomycin therapy. The absolute neutrophil count reached a nadir of 418 cells/mm(3) during vancomycin use and returned to normal 7 days after its discontinuation. The eosinophil count was also elevated during the neutropenic episode and probably related to vancomycin. Based on the Naranjo probability scale, the reaction was probably related to vancomycin use. DISCUSSION: Articles describing cases of vancomycin-induced neutropenia were identified. All patients developed neutropenia as a result of vancomycin therapy >/=12 days. Neutrophil counts generally increased following discontinuation of vancomycin. One article reported successful resolution of neutropenia and infection by switching the patient's therapy to the structurally related antibiotic agent teicoplanin. Other patients were continued on vancomycin therapy, and neutropenia was treated with moderate to good success with filgrastim. Rechallenge was not generally attempted. The mechanism of neutropenia caused by vancomycin is unclear, but appears to be immune-mediated. CONCLUSIONS: Vancomycin therapy should not be prolonged unless absolutely necessary, and therapy should be reserved for patients with clear indications for the drug, such as infections due to gram-positive organisms resistant to other therapies. Patients should have periodic assessment of white blood cell and neutrophil counts with consideration to discontinue vancomycin if neutropenia develops.     

Abnormal responses of myeloid progenitor cells to granulocyte-macrophage colony-stimulating factor in human cyclic neutropenia.

Granulocyte-macrophage progenitors (CFU-GM) from four patients with childhood onset cyclic neutropenia demonstrated abnormal in vitro proliferative responses to purified, recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) when examined in detailed dose-response studies. Marrow aspirate specimens were obtained for these studies from cyclic neutropenia patients (both during neutropenic nadirs and during recovery phases of cycles), from leukemia patients in remission who had received myelosuppressive chemotherapy, and from healthy normal volunteers. Nucleated marrow cells were then isolated by density-gradient centrifugation and cryopreserved to permit studies of CFU-GM from patients and controls to be carried out at the same time and in replicate. Maximum clonal growth of CFU-GM from normal subjects and from individuals recovering from drug-induced myelosuppression was elicited by 20-100 pmol/liter rhGM-CSF, and the CSF concentrations that induced half-maximal responses (ED50) were between 1.0 and 3.0 pmol/liter. In contrast, maximum growth of CFU-GM from the cyclic neutropenia patients required greater than or equal to 1.0 nmol/liter rhGM-CSF and ED50's were greater than 30.0 pmol/liter. These abnormalities in the GM-CSF responsive growth of myeloid progenitors were independent of cycle time and were most apparent with the predominantly neutrophilic 7-d CFU-GM. Moreover, differences in the growth of 14-d CFU-GM could be attributed mostly if not entirely to differences in the generation of neutrophilic colonies. These findings indicate that childhood onset cyclic neutropenia is associated with an underlying disturbance in the GM-CSF responsive growth of myeloid progenitors committed to neutrophilic differentiation.     

Colony-forming cells in culture and colony-stimulating activity of the urine and the serum in a case of cyclic neutropenia.

A 22-year-old female with cyclic neutropenia was studied. Her bone marrow cells showed high colony-forming activity in soft agar through the cycle, though there were slight fluctuations in the number and the shape of colonies. On the other hand, the peak of urinary colong-stimulating activity (CSA) occurred at the neutropenic stage. The dialyzed serum showed two peaks of CSA, i.e., at the peak and the valley of the neutrophil count, although the undialyzed serum showed only one peak at the neutroenic stage. It is suggested on the basis of these data that humoral factors may play a role in maintaining the neutrophil cycle.     

Treatment of carbimazole-induced agranulocytosis and sepsis with granulocyte colony stimulating factor

We present the management of agranulocytosis and neutropenic sepsis secondary to carbimazole with recombinant human granulocyte colony stimulating factor (G-CSF). A 72-year-old woman with a history of thyrotoxicosis presented with sore throat and fever two weeks after starting carbimazole. Investigations confirmed a leucopenia and neutropenia. G-CSF was used as an adjunctive therapy with discontinuation of carbimazole, barrier nursing and a broad-spectrum antibiotic regimen to treat her neutropenic sepsis. Total white cell count and neutrophil count returned to normal and she made an uneventful recovery. She was subsequently rendered euthyroid with radioiodine treatment.     

An adult dog with cyclic neutropenia treated by lentivirus- mediated delivery of granulocyte colony-stimulating factor

Cyclic neutropenia occurs in humans and gray collie dogs, is characterized by recurrent neutropenia, and is treated by daily injections of recombinant granulocyte colony-stimulating factor (G-CSF). After showing that canine recombinant G-CSF increased neutrophil counts in an affected dog, we administered intramuscularly 2 x 10(9) infectious units (IU) of a lentiviral vector encoding canine G-CSF cDNA. Elevated, therapeutic neutrophil production was obtained for nearly 18 months. Lentiviral vector treatment provided a mean neutrophil count of 29,230 +/- 12,930 cells/microl, which was significantly increased over both the pretreatment value (5,240 +/- 4,800 cells/microl; p < 0.0001) and the neutrophil count during G-CSF administration (17,820 +/- 11,100 cells/microl; p < 0.0001). By systemic infusion of recombinant G-CSF to normal dogs we estimated that 2 x 10(9) IU of lentivirus delivered 3.5 microg of G-CSF per kilogram per day. After lentiviral vector treatment the gray collie gained weight, showed no clinical signs of infection and fever, and no longer needed housing in a pathogen-free environment. Genomic DNA harvested from muscle at the injection sites was positive for provirus, whereas gonad, lung, spleen, heart, liver, kidney, and noninjected muscle samples were negative. These studies show that an adult animal is responsive long-term to lentivirus-mediated G-CSF delivery, suggesting this approach may be applied for treatment of adult patients with cyclic and other neutropenias.     

G-CSF在恶性淋巴瘤患者体内诱导ENA-78和IL-8的作用研究

粒细胞集落刺激因子（G-CSF）可以刺激化疗诱导的中性粒细胞减少症患者恢复中性粒细胞计数,并在体外刺激其产生上皮来源的嗜中性粒细胞趋化蛋白-78（ENA-78）和白细胞介素8（IL-8）等趋化因子。本研究旨在探讨G-CSF在体内是否也有类似作用。研究对象为10例接受化疗及G-CSF治疗的淋巴瘤患者,分别在以下时间段采集外周血：化疗前,标记为TimePoint（TPl）;接受G-CSF治疗前的中性粒细胞减少阶段,标记为TP2;接受G-CSF治疗后的中性粒细胞恢复阶段,标记为TP3。采用实时定量PCR检测中性粒细胞内ENA-78和IL-8的mRNA含量,流式细胞术检测其吞噬功能及产生的活性氧（ROS）。结果表明,在TP2阶段,ENA-78mRNA表达升高者5例,儿-8mRNA表达升高者8例;在TP5阶段,ENA-78mRNA表达升高者3例,降低者6例,IL-8mRNA表达降低者7例。结论：中性粒细胞内ENA-78和IL-8的表达升高在化疗后中性粒细胞减少的患者体内较常见,而G-CSF干预对其升高无明显作用。     

A prospective study of neutropenia induced by high doses of beta-lactam antibiotics

A prospective study on the effect of beta-lactam antibiotics on granulopoiesis was carried out in 29 consecutive patients with bacterial endocarditis. Fourteen patients received a high dose of benzylpenicillin, up to 18 g/day, but in only three of them could the treatment be fulfilled as planned, for a mean time of 25 days. In 11 benzylpenicillin treated patients treatment had to be discontinued because of fever, rash or neutropenia. Neutropenia appeared in seven patients after 14-24 (mean 22) days. No superinfection occurred during the neutropenic phase which lasted 2-12 days. Patients with neutropenia differed significantly from others in having a lowered pretreatment neutrophil count (3.2 vs 10.4). In 15 patients treated with other beta-lactams, three cases of fever and rash and one case of neutropenia were seen in patients treated with cloxacillin 12 g daily. It was concluded that a daily dose of 18 g of benzylpenicillin is too high for longer treatment periods and that patients with initial low counts of neutrophils have an increased risk of developing neutropenia.     

Valproic acid-induced neutropenia

OBJECTIVE: To report a case of severe neutropenia caused by valproic acid (VPA). CASE SUMMARY: A 56-year-old white woman with an infectious brain abscess causing tonic-clonic seizure activity was treated with VPA. She developed severe neutropenia after 2 days of VPA therapy. The absolute neutrophil count reached a nadir of 47 cells/mm(3) during VPA use and returned to normal upon its discontinuation. DISCUSSION: VPA is considered to be a well-tolerated antiepileptic drug. While neutropenia has been reported, it has been mild and transient. This patient developed severe neutropenia during effective treatment with VPA, making her significantly susceptible to infection. The Naranjo probability scale indicates VPA as the probable cause of neutropenia in this case. CONCLUSIONS: This report of severe neutropenia caused by VPA emphasizes the importance of monitoring complete blood cell counts during therapy with this agent.     

Filgrastim therapy in acute nonlymphoblastic leukemia

AIM: To specify effects of the granulocytic colony-stimulating factor (G-CSF) in the treatment of acute nonlymphoblastic leukemia. MATERIAL AND METHODS: Thirteen patients with acute myeloid leukemia (AML) were treated in the Hematological Clinic of the Higher Medical Institute in Plovdiv in 1996-1998. All of them received a standard induction therapy with cytosin arabinoside + daunorubicin (7 + 3 days). During the first neutropenic phase (neutrophils < 0.5 x 10(9)/l) G-CSF filgrastim was applied (5 microg/kg/day, s.c.) until a recovery of the neutrophil count reached > 1.0 x 10(9)/l and was maintained for 3 successive days. The control group consisting of patients matched by age, gender, an AML cytomorphologic variant was given the same therapy but filgrastim. RESULTS: The study group showed quicker recovery of the neutrophil count (12.6 vs 16.8 days), reduced febrile period (9.8 vs 12.4 days) and shorter duration of parenteral antibiotic treatment (9.8 vs 12.4 days) compared to controls. No statistically significant difference between both groups was found in the duration of the antimycotic treatment (p > 0.05). No cytological signs of aggravation of basic disease were absent in patients who received filgrastim. CONCLUSION: Administration of G-CSF in AML is useful as it promotes rapid overcoming of neutropenia and its complications.     

Collection efficiency on the fenwal CS3000 when using filgrastim (recombinant methionyl human granulocyte colony-stimulating factor) as a peripheral blood stem cell mobilization agent

The collection efficiency (CE) of the Fenwal CS3000 in collecting peripheral blood stem cells during post-chemotherapy recovery phase ranges from 58% to 73%. Recently filgrastim (recombinant methionyl human granulocyte colony-stimulating factor [G-CSF]) has also been shown to be effective as a mobilization agent although mobilization occurs during elevated and not low normal leukocyte counts. We compared the mononuclear cell (MNC) CE and the myeloid progenitor cell (CFU-GM) CE among 11 patients with G-CSF mobilization (33 procedures) and 19 patients during recovery following myelosuppression chemotherapy (93 procedures). Pre-apheresis leukocyte, neutrophil, MNC, and PB CFU-GM counts were significantly higher in the G-CSF group, while the granulocyte percentage in the apheresis products was similar in both groups. Both MNC CE (81.8 ± 4.5% vs. 64 ± 2.4%) and CFU-GM CE (79.5 ± 10.5% vs. 55.8 ± 3.5%) were higher in the G-CSF group. Only the pre-apheresis MNC count showed an independently significant correlation for both CE (P <.001). The higher CE in the G-CSF group can only be partly explained by a rise in MNC count during apheresis. These data suggest that the blood cell separator works better with leukocytosis, and especially with a higher MNC count. The improvement in CE is another benefit of G-CSF mobilization over chemotherapy mobilization. © 1994 Wiley-Liss, Inc.     

Prolonged neutropenia resulting from antibodies to neutrophil-specific antigen NB1 following marrow transplantation

Marrow graft failure is a significant cause of morbidity following bone marrow transplantation. A case is reported of marrow graft failure due to neutrophil antibodies. A 13-year-old girl with a large granular lymphocytosis and chronic neutropenia was treated with granulocyte transfusions prior to undergoing a transplant with bone marrow from a partially matched, unrelated donor. Following the transplant, a bone marrow biopsy showed engraftment of donor myeloid cells, but the recipient remained neutropenic. Testing of the serum for neutrophil antibodies found that the recipient's serum had a high-titer neutrophil antibody. Immunoprecipitation studies using the marrow recipient's serum and 125I surface-labeled neutrophils showed that the antibody reacted to the neutrophil-specific antigen NB1. Phenotyping of neutrophils from the marrow donor found that they expressed NB1 antigen, and, in a crossmatch assay, the recipient's serum reacted with donor neutrophils. Despite treatment with granulocyte-macrophage– colony-stimulating factor, the marrow transplant recipient remained neutropenic and died of polymicrobial sepsis and aspergillosis 38 days after the transplant. The presence of high-titer antibodies to neutrophil-specific antigen NB1 in this patient following transplant likely prevented the recovery of her peripheral blood neutrophils and contributed to her death.     

Interleukin 1 administration in mice produces hypoferremia despite neutropenia.

To determine whether the hypoferremic response to inflammation requires neutrophils, we administered human recombinant IL-1 to mice made neutropenic with cyclophosphamide. With single intraperitoneal injections of IL-1 the plasma iron concentrations decreased significantly in mice with either normal neutrophil counts or neutropenia. After single injections transferrin concentrations were not significantly changed, but the decrease in serum iron lowered mean transferrin saturations from a baseline of 45 to 24-30% in nonneutropenic mice, and from 99 to 70-77% in neutropenic mice. Similar changes were observed after intraperitoneal injections of Escherichia coli. 4-d continuous infusions of IL-1 also led to reductions in serum iron concentrations, but transferrin concentrations doubled. The combination of a decrease in serum iron and an increase in transferrin concentration after chronic infusion in neutropenic mice led to a greater decline in mean transferrin saturations, from a baseline of 110 to 25%. In mice not given cyclophosphamide, chronic IL-1 infusion was associated with a reduction in mean hemoglobin concentrations from 14.7 to 13.5 g/dl, consistent with restricted availability of iron for erythropoiesis associated with low saturation of transferrin. We conclude that IL-1 can decrease the serum iron despite profound peripheral neutropenia and that transferrin in a positive acute phase reactant in the mouse.     

Periodic Hematopoiesis in Human Cyclic Neutropenia

Human cyclic neutropenia is characterized by severe depression of blood neutrophil levels approximately every 21 days. To investigate the mechanism of cyclic neutropenia four patients were studied with daily complete blood counts, serial bone marrow examinations, marrow reserve testing, serum muramidase determinations, DF²²P granulocytokinetic studies, and, in one patient, in vivo [³H]TdR labeling. Periodogram analysis of the serial blood counts in the latter patient and visual inspection of multiple cycles in the others revealed periodic fluctuations in the levels of blood neutrophils, monocytes, lymphocytes, reticulocytes, and platelets. Rhythmic changes in the morphologic and radioisotopic studies as well as the marrow reserve tests and muramidase measurements were consonant with a mechanism of periodic failure of marrow production rather than peripheral destruction. Human cyclic neutropenia is analogous to cyclic neutropenia in the grey collie dog and may be viewed as the consequence of cyclic hematopoiesis.     

伊曲康唑联合重组人粒细胞集落刺激因子治疗中性粒细胞减少的血液病患者侵袭性真菌感染的疗效及安全性评价

目的 评价伊曲康唑联合重组人粒细胞集落刺激因子（rhG-CSF）治疗中性粒细胞减少的血液病患者合并侵袭性真菌感染的临床疗效及安全性.方法 回顾性分析2007年1月至2011年12月收治的103例血液病合并真菌感染的患者,治疗期间72例患者出现粒细胞缺乏,其中44例患者应用伊曲康唑联合rhG-CSF治疗（治疗组）,28例患者单独应用伊曲康唑治疗（对照组）.结果 治疗组患者有效率为72.73％,对照组为46.43％（P＜0.05）;中性粒细胞≤500/mm3且≥100/mm3的患者抗真菌治疗有效率明显高于中性粒细胞≤100/mm3的患者（P＜0.05）;粒缺持续时间≤10 d的抗真菌治疗有效率明显低于粒缺持续时间＜10 d的患者（P ＜0.05）;72例患者中确诊9例、临床诊断33例、拟诊30例;确诊组有效率低于临床诊断与拟诊组（P＜0.05）,抢先性治疗组（87.50％）和经验性治疗组（64.00％）的有效率均明显高于目标性治疗组（34.78％）,差异有统计学意义（P均＜0.05）.结论 伊曲康唑联合rhG-CSF治疗中性粒细胞减少的血液病患者真菌感染是有效安全的;中性粒细胞减少的程度和时间是影响真菌治疗效果的重要因素.     

Mechanism-based models for topotecan-induced neutropenia

OBJECTIVE: A semiphysiologic pharmacokinetic-pharmacodynamic model was applied to describe topotecan-induced neutropenia, to quantify interindividual and intraindividual pharmacodynamic variability, and to study the effect of covariates on the model. METHODS: Data were obtained from patients treated with topotecan given either orally (118 patients) or intravenously (71 patients), according to different schedules (5 to 21 consecutive days), with or without cisplatin. The model mimics the maturation chain of neutrophils. Topotecan concentration-time profiles affected the proliferation of neutrophil precursors (sensitive cells) through an inhibitory linear model (topotecan is assumed to induce cell loss by a function, E drug, proportional to the topotecan concentration in the central compartment: E drug = Slope . Concentration). The topotecan plasma concentration versus time profile was generated for each patient by modeling the data according to a 2-compartment pharmacokinetic model and first-order absorption for oral administration by use of NONMEM. RESULTS: The model described the time course of neutrophil values well. Topotecan neutropenic effect exhibited a large interpatient variability (coefficient of variation of 82% for the slope values). The oral route was associated with a 43% lower value for slope, corresponding to a lower toxicity. The combination with cisplatin increased the neutropenic effect compared with topotecan alone by a factor 3.5. The intrapatient variability between cycle 1 and cycle 2 on slope was lower for the intravenous administration than for the oral administration. By application of the model to a new weekly schedule of topotecan, neutrophil values at the nadir were consistent with those observed during a phase I study of this regimen. CONCLUSION: This model can be used to describe both the duration and intensity of neutropenia; the area between the curve of neutrophil count versus time and a critical neutrophil count (such as 0.500 x 10(3) /mm 3 ) would be a better toxic endpoint than the unique observed value of neutrophil at nadir. The model may be used to predict neutropenia corresponding to regimens of topotecan not yet explored.