Docetaxel and carboplatin is an active regimen in advanced non-small-cell lung cancer: a phase II study in Caucasian and Asian patients.

BACKGROUND: The purpose of this study was to report response rates, survival and toxicity in advanced non-small-cell lung cancer (NSCLC) following docetaxel and carboplatin, and to explore potential differences in these end points between Caucasian and Asian patients. PATIENTS AND METHODS: Sixty-eight patients of good performance status with Stage IIIB or IV NSCLC were entered on a phase II study at three sites in Australia and Singapore. Docetaxel 75 mg/m2 and carboplatin AUC 6 were given every 3 weeks. Response to treatment and toxicity were graded by standard criteria. The Kaplan-Meier method was used to estimate survival rates, and subgroups compared by the log-rank test. Cox's proportional hazards regression was used to determine which potentially explanatory variables independently affected the outcome. RESULTS: The response rate was 39% (95% confidence interval 27% to 52%), and 42% in evaluable patients. Response occurred in 65% of Asian and 31% of Caucasian patients (P = 0.01). Ethnicity was the only significant predictor of response in multivariate analysis. The 1-year survival rate was 53%. Performance status (P = 0.021), ethnicity (P = 0.035) and presence of bone or liver metastases (P = 0.011) were independent predictors of overall survival. Neutropenia (grade IV in 73% of patients), febrile neutropenia (26% patients) and diarrhea (grade III/IV in 11% of patients) were the major treatment related toxicities. A high rate (three of six) of febrile neutropenia in Singapore, including one treatment-related death in the initial patients treated, resulted in a reduction in the carboplatin dose to AUC 4.5 at that site. CONCLUSIONS: This regimen is active in advanced NSCLC. The potential impact of ethnicity on efficacy and toxicity of treatment requires further investigation.

Patterns of failure with increasing intensification of induction chemotherapy for acute myeloid leukaemia.

Patterns of failure were studied in two consecutive randomized trials of intensified induction therapy carried out by the Australian Leukaemia Study Group (ALSG) between 1984 and 1991 to determine the impact of dose intensification. Patients received standard dose cytarabine and daunorubicin (7-3), 7-3 plus etoposide (7-3-7) or 7-3 plus high-dose cytarabine (HIDAC-3-7) chemotherapy. Patients with FAB M3 morphology were excluded. Time to failure (TTF) was defined as the time from randomization to induction death or removal from study for non-responders, or to relapse or death in complete response (CR) for complete responders. An estimated 86% of 470 de novo patients with acute myeloid leukaemia failed within 10 years of randomization, as a result of death in induction in 17% of the randomized patients, failure to achieve CR in a further 17%, relapse in 44% and death in CR in 8% of patients. An estimated 66% of patients failed as a result of refractory disease or relapse within that period (disease-related failures). Multifactor analysis identified age and peripheral blast count as the most significant pretreatment factors associated with overall TTF. These factors, together with cytogenetics, were significantly associated with disease-related failures. High-dose cytarabine in induction significantly decreased the disease-related failure rate as did allogeneic transplantation in first CR. The impact of high-dose cytarabine did not depend on the cytogenetic risk group.

BDNF synthesis in spiral ganglion neurons is constitutive and CREB-dependent.

Brain-derived neurotrophic factor (BDNF), which supports spiral ganglion neuron (SGN) survival in vivo and in vitro, is synthesized by SGNs. The BDNF gene generates multiple different transcripts, each from its own promoter region. Using reverse transcriptase-polymerase chain reaction (RT-PCR), we find that SGNs express only the downstream transcripts III and IV in vivo and in vitro. Using RT-PCR assays of BDNF transcripts and transfection of BDNF promoter-reporter constructs, we tested the hypothesis, originally derived from studies of cortical neurons, that depolarization induces BDNF expression via a signaling pathway that includes Ca2+/calmodulin-dependent kinases (CaMKs) and the transcription factor, Ca2+/cyclic AMP response element binding protein (CREB). In contrast, we found that in SGNs in vivo BDNF expression is constitutive and is not increased by electrical activation. Similarly, BDNF expression in vitro is not increased by stimuli that activate CREB, including depolarization, cAMP, or transfection of activated CaMK mutants. However, transfection of dominant-negative CREB mutants did abrogate gene expression driven by BDNF promoters III and IV, indicating that CREB is necessary for constitutive BDNF expression. Thus, BDNF synthesis within SGNs makes possible an autocrine or paracrine mechanism that can contribute to support SGN survival but SGNs are distinctive in that this mechanism is constitutive and not activity-regulated.

Highly sensitive analysis of the antifolate pemetrexed sodium, a new cancer agent, in human plasma and urine by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatography method was developed and validated for the quantitation of pemetrexed (LY231514, ALIMTA) in human urine and plasma. Plasma samples were spiked with the internal standard lometrexol and extracted using Certify II columns. Pemetrexed was assayed in diluted urine by an external calibration method. A C8 column was used for the separation of analytes with a mobile phase composed of sodium formate buffer and acetonitrile. Between- and within-day precision and accuracy were acceptable down to the limit of quantitation of 5 ng/ml in plasma. This method was used successfully for an investigation of the disposition of pemetrexed in patients receiving 500 mg/m2 as a 10-min infusion.

Frequency of cytochrome P450 3A4 variant genotype in transplant population and lack of association with cyclosporin clearance.

OBJECTIVE: Cytochrome P450 3A4 (CYP3A4) plays a vital role in the oxidative metabolism of many xenobiotics. Some recent reports have provided circumstantial evidence in support of an association between a genetic polymorphism (A-->G) in the 5'-flanking region (-290) of CYP3A4 and altered enzyme activity. We sought to determine whether genotyping patients for CYP3A4-G could assist with the dose optimisation of drugs metabolised by this system. METHODS: Normal subjects and renal-transplant patients receiving cyclosporin for immune modulation were genotyped for the CYP3A4-G variant. A surrogate for cyclosporin clearance was estimated from the ratio of the cyclosporin dose, normalised for body weight and the corresponding trough concentration. The association between genotype and clearance was examined in patients who received twice-daily doses of cyclosporin and who were not on concurrent medication known to modify CYP3A4 function. RESULTS: The allelic frequencies of the CYP3A4-G variant were estimated to be 2.6% and 3% in transplant patients and normal subjects, respectively. The median cyclosporin pseudo-clearance of transplant patients with wild-type CYP3A4 was 0.90 l/h/kg (range: 0.35-3.8 l/h/kg; n = 86), whereas the corresponding value for the five patients heterozygotic for the CYP3A4-G variant was 0.71 l/h/kg (range 0.35-0.91 l/h/kg). The distribution of the pseudo-clearance according to genotype was not found to be significant according to a Fisher's exact test (P = 0.15). CONCLUSION: Genotyping for the CYP3A4-G polymorphism is unlikely to assist cyclosporin dose selection in transplant patients.

Optimizing the erythromycin breath test for use in cancer patients.

The erythromycin breath test (EBT) is a putative in vivo probe for drug metabolism by cytochrome P450 3A4 (CYP3A4). Because many anticancer drugs are metabolized by this system, we sought to further develop the EBT as a tool for predicting the clearance, in cancer patients, of drugs metabolized by CYP3A4. Sixteen adult patients with incurable cancer were studied. The EBT was performed on day 1 and breath sampled after the i.v. injection of 4 microCi of 14C-erythromycin. The breath 14CO2 flux (CERt) was estimated at 11 time points over 2 h. On day 2, the EBT was repeated midway through a 10-min infusion of 100 mg of erythromycin lactobionate, and the plasma pharmacokinetics of erythromycin were determined. The infusion of 100 mg of erythromycin did not modify the EBT results significantly. The values of the conventional EBT parameter CER20 min obtained on day 1 were comparable for most subjects (0.03-0.06% dose/min), with the exception of an individual receiving the known CYP3A4 inducers dexamethasone and phenytoin who returned a value of 0.14% dose/min. There was no significant correlation between any of the conventional EBT parameters and erythromycin clearance. However, two parameters reflecting early emergence of breath radioactivity (1/TMAX and CER3 min/CERMAX) correlated significantly with erythromycin clearance (P = 0.005 and 0.006, respectively). Novel parameters derived from the EBT are significantly correlated with the clearance of erythromycin even in the presence of confounding factors, such as metastatic liver disease, altered protein binding, and comedication. These parameters may enable dose optimization of cytotoxics metabolized by CYP3A4.

Enhanced vulnerability to oxidative stress by alpha-synuclein mutations and C-terminal truncation.

alpha-Synuclein is a key component of Lewy bodies found in the brains of patients with Parkinson's disease and two point mutations in this protein, Ala53Thr and Ala30Pro, are associated with rare familial forms of the disease. Several lines of evidence suggest the involvement of oxidative stress in the pathogenesis of nigral neuronal death in Parkinson's disease. In the present work we studied the effects of changes in the alpha-synuclein sequence on the susceptibility of cells to reactive oxygen species. Human dopaminergic neuroblastoma SH-SY5Y cells were stably transduced with various isoforms of alpha-synuclein and their survival following exposure to hydrogen peroxide or to the dopaminergic neurotoxin MPP(+) was assessed. Cells expressing the two point mutant isoforms of alpha-synuclein were significantly more vulnerable to oxidative stress, with the Ala53Thr engineered cells faring the worst. In addition, cells expressing C-terminally truncated alpha-synuclein, particularly the 1-120 residue protein, were more susceptible than control beta-galactosidase engineered cells. The present experiments indicate that point mutations and C-terminal truncation of alpha-synuclein exaggerate the susceptibility of dopaminergic cells to oxidative damage. Thus, these observations provide a pathogenetic link between alpha-synuclein aberrations and a putative cell death mechanism in Parkinson's disease.

Clinical pharmacokinetics of the irinotecan metabolite 4-piperidinopiperidine and its possible clinical importance.

PURPOSE: To investigate the clinical relevance of 4-piperidinopiperidine (4PP) in the activity of irinotecan (CPT-11), a high-performance liquid chromatography-turboionspray-tandem mass spectrometry assay for plasma 4PP was developed. METHODS: Plasma samples were prepared for analysis following C18 solid-phase extraction. Chromatography was performed on a Waters Nova-Pak Phenyl column. Selected reaction monitoring with the mass transitions m/z 169.2 --> 84.2 and 139.2 --> 98.1 was used for the detection of 4PP and the internal standard (IS), 1-piperidineproprionitrile, respectively. RESULTS: The assay was linear from 14.8 to 591.0 nM with absolute recoveries of 4PP (59.1 nM) and IS (143.7 nM) of 85.7% (n = 10) and 86.7% (n = 10), respectively. The accuracy and imprecision of the method (total) was > or = 96.8% and < or = 8.5% over the concentration range studied, respectively. 4PP was detectable in plasma following the administration of 125, 350, 500 mg/m2 and 600 mg/m2 CPT-11 to patients, with AUC(4PP) correlated with the dose (r2 = 0.66). Plasma concentrations of 4PP declined slowly with a long terminal half-life (33.4 +/- 17.1 h). CONCLUSIONS: Overall, the concentrations of 4PP in plasma were in the sub-micromolar range (< 206.9 nM) and substantially lower than those capable of inducing apoptosis of cancer cells.

A pharmacokinetic and phase II study of gallium nitrate in patients with non-small cell lung cancer.

This study investigated the pharmacokinetics and activity of gallium nitrate in non-small cell lung cancer when 700 mg/m2 was given as a 30-min infusion with prehydration every 2 weeks. Gallium was measured in plasma and urine using flameless atomic absorption spectrophotometry, and pharmacokinetics of total and ultrafilterable gallium were calculated. Twenty-five patients with non-small cell lung cancer received 1-12 (median 2) courses of gallium nitrate every 2 weeks. Of 21 patients evaluable for response, 1 partial response was recorded, 4 patients had stable disease. and 16 had progressed. The most serious toxicities were renal impairment and optic neuritis. Hypocalcaemia was recorded in 3 patients. The mean C(max) was 15.2 +/- 3.1 microg/ ml (range 9.5-21.2). Most gallium remained ultrafilterable for the first 10 h, after which plasma protein binding increased, and at 48 h only 11% was present as ultrafilterable gallium. The elimination profiles of both total and ultrafilterable gallium were biphasic, and the distribution phase consisted of ultrafilterable gallium, with a distribution half-life of 1.4 h. Total gallium plateaued at 1.9 microg/ml at between 8 and 12 h, and the estimated elimination half-life was 63 h. The elimination half-life of ultrafilterable gallium was 16.5 h. Inter- and intra-patient variability in pharmacokinetics was minimal. A mean of 50 +/- 14% of the gallium dose was excreted in the urine within 48 h. A short infusion of gallium nitrate achieving high peak plasma concentrations results in little efficacy in non-small cell lung cancer.

Degradation of alpha-synuclein by proteasome.

Mutations in alpha-synuclein are known to be associated with Parkinson's disease (PD). The coexistence of this neuronal protein with ubiquitin and proteasome subunits in Lewy bodies in sporadic disease suggests that alterations of alpha-synuclein catabolism may contribute to the pathogenesis of PD. The degradation pathway of alpha-synuclein has not been identified nor has the kinetics of this process been described. We investigated the degradation kinetics of both wild-type and A53T mutant 6XHis-tagged alpha-synuclein in transiently transfected SH-SY5Y cells. Degradation of both isoforms followed first-order kinetics over 24 h as monitored by the pulse-chase method. However, the t((1)/(2)) of mutant alpha-synuclein was 50% longer than that of the wild-type protein (p < 0.01). The degradation of both recombinant proteins and endogenous alpha-synuclein in these cells was blocked by the selective proteasome inhibitor beta-lactone (40 microM), indicating that both wild-type and A53T mutant alpha-synuclein are degraded by the ubiquitin-proteasome pathway. The slower degradation of mutant alpha-synuclein provides a kinetic basis for its intracellular accumulation, thus favoring its aggregation.

A phase I and pharmacokinetic study of paclitaxel and epirubicin in advanced cancer.

The objectives of this phase I trial were to determine the maximally tolerated doses of the combination of epirubicin and paclitaxel with and without G-CSF (granulocyte colony stimulating factor) support and to investigate whether epirubicin pharmacokinetics are altered by paclitaxel. Patients with advanced cancer, performance status 0-2, and a normal left ventricular ejection fraction who had received up to 1 prior chemotherapy regimen were treated with epirubicin followed by a 3-hour infusion of paclitaxel repeated every 3 weeks. Dose levels studied were (paclitaxel/epirubicin) 155/75, 175/75, 175/90, 200/90 mg/m2 without G-CSF and 175/90 mg/m2 with G-CSF. Thirty-five patients were entered and all were assessable for toxicity. The dose-limiting dose level was 175 mg/m2 paclitaxel and 90 mg/m2 epirubicin with limiting toxicities of febrile neutropenia, diarrhea and esophagitis. The addition of G-CSF did not allow escalation of epirubicin. No significant cardiac toxicity was observed. Epirubicin pharmacokinetics were studied during the first 2 cycles in 6 patients, who were randomized to receive 1 cycle with no interval between the completion of the epirubicin and the commencement of the paclitaxel infusion and the other cycle with a 72-hour interval between the drugs. There was no substantial effect of paclitaxel on epirubicin or epirubicinol pharmacokinetics, although there was a marginal increase in glucoronidation. In conclusion, paclitaxel 175 mg/m2 and epirubicin 75 mg/m2 is recommended for phase II and III studies.

Initial paclitaxel improves outcome compared with CMFP combination chemotherapy as front-line therapy in untreated metastatic breast cancer.

PURPOSE: To determine the place of single-agent paclitaxel compared with nonanthracycline combination chemotherapy as front-line therapy in metastatic breast cancer. PATIENTS AND METHODS: Patients with previously untreated metastatic breast cancer were randomized to receive either paclitaxel 200 mg/m(2) intravenously (IV) over 3 hours for eight cycles (24 weeks) or standard cyclophosphamide 100 mg/m(2)/d orally on days 1 to 14, methotrexate 40 mg/m(2) IV on days 1 and 8, fluorouracil 600 mg/m(2) IV on days 1 and 8, and prednisone 40 mg/m(2)/d orally on days 1 to 14 (CMFP) for six cycles (24 weeks) with epirubicin recommended as second-line therapy. RESULTS: A total of 209 eligible patients were randomized with a median survival duration of 17.3 months for paclitaxel and 13.9 months for CMFP. Multivariate analysis showed that patients who received paclitaxel survived significantly longer than those who received CMFP (P =.025). Paclitaxel produced significantly less severe leukopenia, thrombocytopenia, mucositis, documented infections (all P <.001), nausea or vomiting (P =.003), and fever without documented infection (P =.007), and less hospitalization for febrile neutropenia than did CMFP (P =.001). Alopecia, peripheral neuropathy, and myalgia or arthralgia were more severe with paclitaxel (all P <.0001). Overall, quality of life was similar for both treatments (P > = .07). CONCLUSION: Initial paclitaxel was associated with significantly less myelosuppression and fewer infections, with longer survival and similar quality of life and control of metastatic breast cancer compared with CMFP.

A phase I/II study of intensive dose escalation of cytarabine in combination with idarubicin and etoposide in induction and consolidation treatment of adult acute myeloid leukemia. Australian Leukaemia Study Group (ALSG).

To determine the safety and efficacy of the combination of idarubicin, cytarabine and etoposide ("ICE") for induction and consolidation treatment of acute myeloid leukemia (AML), and of dose-intensification of cytarabine in this setting, 54 previously untreated patients in three cohorts were studied by sequential dose escalation of cytarabine, in combination with standard doses of idarubicin and etoposide. Cytarabine was given to Cohort 1 at the conventional dosage of 100 mg/m2 per day by continuous infusion for 7 days in induction and 5 days in consolidation; to Cohort 2 at high-dose (HiDAC) (3 g/m2 intravenously twice daily on days 1, 3, 5 and 7) during induction with conventional dosage during consolidation; to Cohort 3 HiDAC was given for both induction and consolidation. In addition, Cohort 3 patients received lenograstim (Granocyte; rHuG-CSF) after both induction and consolidation courses. We found that there was no significant difference between the three cohorts in hematological toxicity in induction, but that HiDAC was associated with a greater incidence of gastro-intestinal toxicities. There was no difference in induction mortality between the three cohorts, which was 11% overall. Consolidation with HiDAC led to a significant increase in hematological toxicity. Overall, the complete remission (CR) rate was 80% with no significant difference between the three regimens. The estimated disease free survival at 3 years was 28%, 67% and 54% respectively for Cohorts 1, 2 and 3 with an estimated overall survival of 38%, 63% and 47%. We conclude that cytarabine dosage can be escalated safely in combination with idarubicin and etoposide in both induction and consolidation. The combination is effective for induction treatment of AML and its side-effects appear similar to those of standard regimens. Whether its use offers long-term benefits compared with standard regimens is the subject of ongoing controlled randomized studies.

Adult acute myeloid leukaemia: update on treatment.

Adult acute myeloid leukaemia (AML) is uncommon, with an age-standardised incidence of approximately 3 per 100,000. Patients present (median age, > 60 years) with evidence of bone marrow failure, anaemia, leukopenia or thrombocytopenia and their sequelae, or AML is detected incidentally by a full blood count. Treatment for AML aims to eliminate leukaemia from bone marrow with intensive chemotherapy: age (over or under 60 years) and performance status determines whether standard or high-dose chemotherapy can be used, but fewer than half the patients with AML are under 60 years. Supportive therapy during initial induction chemotherapy is needed to control neutropenic sepsis and thrombocytopenic bleeding, and to ameliorate the side effects of chemotherapy. Standard induction chemotherapy produces complete remission in 56%-74% of patients; 20% are long term survivors; 10%-15% of patients die in the induction period. Allogeneic haemopoietic stem cell transplantation is recommended in patients under 50 years with an HLA- compatible sibling, with the best outcomes achieved in patients transplanted in first complete remission. It can also provide long term survival in patients who fail to achieve remission after induction therapy. The outcome of AML has improved, particularly for younger patients, but treatment outcomes for older patients and those with secondary leukaemia are still unsatisfactory. The mean overall survival of patients in randomised studies treated with standard therapy is still only 9-15 months.

Low-dose versus standard-dose lenograstim prophylaxis after chemotherapy: a randomized, crossover comparison.

PURPOSE: Granulocyte colony-stimulating factor (G-CSF) administered prophylactically after chemotherapy reduces the duration and severity of neutropenia. This randomized crossover study was designed to assess whether a lower dose of G-CSF is as effective as a standard dose of 5 microg/kg daily. PATIENTS AND METHODS: Patients who received standard-dose chemotherapy regimens expected to cause neutropenia received G-CSF (lenograstim) that started the day after chemotherapy for 14 days or until the absolute neutrophil count (ANC) recovered to greater than 10 x 10(9)/L. The lenograstim dose was randomly allocated to be 2 or 5 microg/kg daily in the first cycle of chemotherapy and crossed over to the alternate dose for the second cycle. The study was designed to accrue 40 assessable patients to provide a power of 80% to detect a difference in duration of neutropenia of 1 day. Fifty-two patients were randomized to treatment and 43 patients completed two cycles of identical chemotherapy. RESULTS: There was little neutropenia irrespective of the dose used. Twenty-three patients (53%) had no grade III or IV neutropenia and 30 patients (70%) had no grade IV neutropenia. Crossover trial methodology was used to assess the difference in outcome caused by the lower dose compared with the standard dose (estimated treatment effect). There was no significant difference in the measures of neutropenia, hospitalization, or other clinical outcomes. The 95% confidence interval (one-sided) for the additional duration of neutropenia caused by the lower dose of lenograstim was 0.43 days or less for grade III or IV neutropenia and 0.34 days or less for grade IV neutropenia. CONCLUSION: Lenograstim 2 microg/kg provides similar protection to 5 microg/kg against neutropenia that complicates standard-dose chemotherapy. The use of a lower dose has important implications for the cost-effectiveness of prophylactic G-CSF therapy.

Phase I trial of cremophor EL with bolus doxorubicin.

Cremophor EL (cremophor), a component of the paclitaxel formulation, can potentially reverse P-glycoprotein-associated multidrug resistance. A Phase I trial of cremophor as a 6-h infusion every 3 weeks was performed with bolus doxorubicin (50 mg/m2). The cremophor dose was escalated from 1 to 60 ml/m2. A standard paclitaxel premedication was given before cremophor. Using a bioassay, potentially active cremophor levels (> or = 1 microl/ml) were measured in plasma from patients receiving cremophor doses of 30, 45, and 60 ml/m2. A cross-over design was used to assess the influence of cremophor 30 ml/m2 on the pharmacokinetics of doxorubicin and doxorubicinol. The plasma area under the concentration versus time curve (AUC) of doxorubicin increased from 1448 +/- 350 to 1786 +/- 264 ng/ml x h (P = 0.02) in the presence of cremophor, whereas the AUC of doxorubicinol increased from 252 +/- 104 to 486 +/- 107 ng/ml x h (P = 0.02). This pharmacokinetic interaction was associated with significantly increased neutropenia. With reduction of the doxorubicin dose to 35 mg/m2, the cremophor dose was increased to 60 ml/m2. Dose-limiting toxicities occurred in two of six patients after 45 ml/m2 and two of four patients after 60 ml/m2, which included febrile neutropenia and grade III cremophor-related toxicities of rash, pruritus, headache, and hypotension. All patients who received 45 ml/m2 cremophor reached plasma levels > or = 1.5 microl/ml, but at 60 ml/m2, only two of four reached this level, and the calculated plasma clearance of cremophor was significantly faster at this dose. One patient with hepatoma resistant to epirubicin achieved a near-complete response. Cremophor 45 ml/m2 over 6 h with 35 mg/m2 doxorubicin is recommended for further studies. The pharmacokinetic interaction between cremophor and doxorubicin is quantitatively similar to that described in trials of paclitaxel with doxorubicin and suggests that the cremophor in the paclitaxel formulation is responsible.

Dose escalation study of carboplatin and cyclophosphamide with filgrastim support: a phase I study.

This clinical trial was designed to explore dose escalation of carboplatin and cyclophosphamide when supported with filgrastim. Twenty-seven patients who had advanced solid tumors received up to six cycles of treatment; a total of 92 cycles of chemotherapy were delivered. Two control groups received standard-dose carboplatin (300 mg/m2) and cyclophosphamide (600 mg/m2), with and without filgrastim. Subsequently, the doses of both carboplatin and cyclophosphamide were increased simultaneously by 50% of the standard dose in sequential cohorts. Doses of up to 2.5 times the standard dose were explored. A final dose of carboplatin, 600 mg/m2, and cyclophosphamide, 1,500 mg/m2, was tested in 4 patients. The duration of neutropenia was brief, even at the highest dose levels. The mean duration of grade 3 or 4 neutropenia was 5.8 days at standard dose without filgrastim and 5.4 days at 2.5 times standard dose with filgrastim. More severe neutropenia was more prolonged at higher doses but remained brief in duration. The mean duration of neutropenia of less than 100 x 10(6)/l was 0.4 days at standard dose without filgrastim and 1.3 days at 2.5 times standard dose. There was no evidence of cumulative neutropenia over repeated cycles of treatment. In contrast, thrombocytopenia was both dose limiting and cumulative. The mean duration of grade 3 or 4 thrombocytopenia was 1.6 days at standard dose and 9.6 days at 2.5 times standard dose. An average of 2.3 platelet transfusions per cycle of treatment was required at the highest dose. Thrombocytopenia was worse with repetitive cycles of therapy. The mean duration of grade 3 or 4 thrombocytopenia was 2.2 days after the first cycle of chemotherapy and 7.8 days after cycle four. The maximum tolerated dose, as defined prospectively, was not reached but further dose escalation was not thought to be warranted because of the severity of thrombocytopenia. When supported with filgrastim, carboplatin and cyclophosphamide can be administered safely with substantially increased dose and acceptable toxicity.