Carboplatin and etoposide pharmacokinetics in patients with testicular teratoma

Inability of Current Dosing to Achieve Carboplatin Therapeutic Targets in People with Advanced Non-Small Cell Lung Cancer: Impact of Systemic Inflammation on Carboplatin Exposure and Clinical Outcomes

BACKGROUND

The presence of elevated systemic inflammation in people with advanced non-small cell lung cancer (NSCLC) is associated with significantly shorter survival following carboplatin-based chemotherapy.

OBJECTIVE

This study investigated whether novel factors, such as systemic inflammation [platelet-lymphocyte ratio (PLR) and neutrophil-lymphocyte ratio (NLR)], impact carboplatin pharmacokinetics and drug utilisation. The study also examined the ability of current and alternate dosing regimens to meet therapeutic targets.

METHODS

Seventy-two people with advanced NSCLC treated with carboplatin-based (460-1050 mg) doublet chemotherapy were recruited and pharmacokinetic data (n = 61) were analysed using non-linear mixed modelling. Covariate analysis was performed to investigate the impact of standard and novel patient characteristics of carboplatin pharmacokinetics. A Monte Carlo simulation of 100,000 representative NSCLC patients evaluated the ability of the Calvert formula and novel dosing strategies to achieve the targeted therapeutic range. The associations between systemic inflammation and chemotherapy drug utilisation (cycles received, relative dose intensity (RDI) and second-line uptake) and clinical endpoints were also investigated in the pharmacokinetic cohort, and two independent cohorts of people with advanced NSCLC from the Chemotherapy Dosing in Cancer-Related Inflammation (CDCRI) database that were administered carboplatin-paclitaxel (n = 37) or carboplatin-gemcitabine (n = 358).

RESULTS

In all cohorts, 25-53% of people had elevated systemic inflammation (NLR > 5 or PLR > 300). In the pharmacokinetic cohort, no patients achieved the desired therapeutic target of carboplatin. Carboplatin exposure was related to renal function, as estimated using the Cockcroft-Gault formula, albumin and inflammation (NLR). In the pharmacokinetic cohort, increasing carboplatin area under the curve (AUC) correlated with greater reductions in red blood cells and haemoglobin. In this cohort, the average measured AUC of partial responders was 2.4 mg·min/mL. Also in the pharmacokinetic cohort, only 12% of people with an NLR > 5 received four or more cycles of chemotherapy, compared with 62% of patients with an NLR ≤ 5 (p < 0.001). For people in the CDCRI cohort receiving carboplatin-gemcitabine, those with an NLR > 5 also received less cycles (four or more cycles, 41% vs. 60%; p < 0.01) as well as less second-line chemotherapy (46% vs. 60%; p = 0.02) compared with patients without inflammation. People in the pharmacokinetic cohort with an NLR > 5 had 12 months less median survival compared with people with an NLR ≤ 5 (6.5 vs. 18 months; p = 0.08). Similarly, overall survival was significantly shortened in people in the CDCRI cohort receiving carboplatin-gemcitabine with an NLR > 5 compared with those with an NLR ≤ 5 (7 vs. 12 months; p < 0.001), and Cox regression analysis showed a 1.5-fold (1.3-2.1; p < 0.001) increased hazard of death associated with the increased systemic inflammation. Simulations of the newly developed model-based and Calvert dosing assessed the ability to reach this study's proposed actual target AUC of 2.2-2.6 mg·min/mL. These showed current Calvert dosing was predicted to result in substantial overexposure in patients with high systemic inflammation. The newly developed model showed equivalent levels of carboplatin therapeutic target achievement across the spectrum of inflammation observed in the lung cancer population.

CONCLUSION

An alternate model-based dosing strategy for carboplatin was developed and is predicted to result in consistent drug exposure across the population and improve attainment of therapeutic targets. Further studies of this new model are warranted in people with advanced NSCLC.

Population pharmacokinetics of carboplatin, etoposide and melphalan in children: a re-evaluation of paediatric dosing formulas for carboplatin in patients with normal or mild impairment of renal function

AIMS

Carboplatin dosage is calculated by using the estimated glomerular filtration rate (GFR) to achieve a target plasma area under the plasma concentration-time curve (AUC). The aims of the present study were to investigate factors that influence the pharmacokinetics of carboplatin in children with high-risk neuroblastoma, and whether target exposures for carboplatin were achieved using current treatment protocols.

METHODS

Data on children receiving high-dose carboplatin, etoposide and melphalan for neuroblastoma were obtained from two study sites [European International Society for Paediatric Oncology (SIOP) Neuroblastoma study, Children's Hospital at Westmead; n = 51]. A population pharmacokinetic model was built for carboplatin to evaluate various dosing formulas. The pharmacokinetics of etoposide and melphalan was also investigated. The final model was used to simulate whether target carboplatin AUC (16.4 mg ml^-1 ·min) would be achieved using the paediatric Newell formula, modified Calvert formula and weight-based dosing.

RESULTS

Allometric weight was the only significant, independent covariate for the pharmacokinetic parameters of carboplatin, etoposide and melphalan. The paediatric Newell formula and modified Calvert formula were suitable for achieving the target AUC of carboplatin for children with a GFR <100 ml min^-1 1.73 m^-2 but not for those with a GFR ≥100 ml min^-1 1.73 m^-2 . A weight-based dosing regimen of 50 mg kg^-1 achieved the target AUC more consistently than the other formulas, regardless of renal function.

CONCLUSIONS

GFR did not appear to influence the pharmacokinetics of carboplatin after adjusting pharmacokinetic parameters for weight. This model-based approach validates the use of weight-based dosing as an appropriate alternative for carboplatin in children with either mild renal impairment or normal renal function.

Classical and Targeted Anticancer Drugs: An Appraisal of Mechanisms of Multidrug Resistance

The mechanisms by which tumor cells resist the action of multiple anticancer drugs, often with widely different chemical structures, have been pursued for more than 30 years. The identification of P-glycoprotein (P-gp), a drug efflux transporter protein with affinity for multiple therapeutic drugs, provided an important potential mechanism and further work, which identified other members of ATP-binding cassette (ABC) family that act as drug transporters. Several observations, including results of clinical trials with pharmacological inhibitors of P-gp, have suggested that mechanisms other than efflux transporters should be considered as contributors to resistance, and in this review mechanisms of anticancer drug resistance are considered more broadly. Cells in human tumors exist is a state of continuous turnover, allowing ongoing selection and "survival of the fittest." Tumor cells die not only as a consequence of drug therapy but also by apoptosis induced by their microenvironment. Cell death can be mediated by host immune mechanisms and by nonimmune cells acting on so-called death receptors. The tumor cell proliferation rate is also important because it controls tumor regeneration. Resistance to therapy might therefore be considered to arise from a reduction of several distinct cell death mechanisms, as well as from an increased ability to regenerate. This review provides a perspective on these mechanisms, together with brief descriptions of some of the methods that can be used to investigate them in a clinical situation.

Extension of the Calvert formula to patients with severe renal insufficiency

PURPOSE

The Calvert formula was derived from the study among patients with glomerular filtration rates (GFRs) of 33-135 ml/min, and it remains unclear whether the formula can be used to calculate optimal and safe dosages of carboplatin in patients with severe renal insufficiency. We evaluated the utility of this formula in patients with severe renal insufficiency.

METHODS

For pharmacokinetic analysis, we studied nine adult Japanese patients with advanced cancer who had an estimated GFR of lower than 30 ml/min/1.73 m(2), as calculated by the Japanese equation for estimating GFR, or who were receiving hemodialysis. The dose of carboplatin was calculated with the Calvert formula, in which GFR was measured by inulin clearance or was assumed to be 0 in patients requiring hemodialysis. Hemodialysis was started 23 h after the end of carboplatin infusion.

RESULTS

Although there was a significant correlation between the estimated and measured carboplatin clearance, the estimated clearance was consistently higher than the measured clearance [mean prediction error ± standard deviation = 41.0 ± 26.3 %] in all seven patients with renal insufficiency (GFR, median 21.4, range 7.8-31.4 ml/min) and in the two hemodialysis patients. Actual areas under the concentration-time curve (AUC) (mg/ml min) were 5.4, 5.7, 6.2, and 9.0 for the four patients with a target AUC (mg/ml min) of 5; 5.7, 6.2, and 7.1 for the three patients with a target AUC (mg/ml min) of 4; and 5.1 and 8.7 for the two hemodialysis patients with a target AUC (mg/ml min) of 5. The measured clearance of carboplatin ranged from 23.0 to 51.3 ml/min in the seven patients not receiving hemodialysis. The pre-hemodialysis carboplatin clearance in the hemodialysis patients was 20.5 and 11.1 ml/min, respectively.

CONCLUSION

For adult patients with severe renal insufficiency, the Calvert formula causes carboplatin overdosing by overestimating the carboplatin clearance.

Pharmacokinetic Optimisation of Treatment with Oral Etoposide

Etoposide is a derivative of podophyllotoxin widely used in the treatment of several neoplasms, including small cell lung cancer, germ cell tumours and non-Hodgkin's lymphomas. Prolonged administration of etoposide aims for continuous inhibition of topoisomerase II, the intracellular target of etoposide, thus preventing tumour cells from repairing DNA breaks. However, the clinical advantages of extended schedules as compared with conventional short-term infusions remain unclear. Oral administration of etoposide represents the most feasible and economic strategy to maintain effective concentrations of drug for extended times. Nevertheless, the efficacy of oral etoposide therapy is contingent on circumventing pharmacokinetic limitations, mainly low and variable bioavailability. Inhibition of small bowel and hepatic metabolism of etoposide with specific cytochrome P450 inhibitors or inhibition of the intestinal P-glycoprotein efflux pump have been attempted to increase the bioavailability of oral etoposide, but the best results were obtained with daily oral administration of low etoposide doses (50-100 mg/day for 14-21 days). Saturable absorption of etoposide was reported for doses greater than 200 mg/day, whereas lower doses were associated with increased bioavailability, although they were characterised by high inter- and intrapatient variability. Pharmacokinetic parameters such as plasma trough concentration between two oral administrations (C(24,trough)), drug exposure time above a threshold value and area under the plasma concentration-time curve have been correlated with the pharmacodynamic effect of oral etoposide. Pharmacokinetic-pharmacodynamic relationships indicate that severe toxicity is avoided when peak plasma concentrations do not exceed 3-5 mg/L and C(24,trough) is under the threshold limit of 0.3 mg/L. To maintain effective etoposide plasma concentrations during prolonged oral administration, pharmacokinetic variability must be monitored in each patient, taking account of factors from many pharmacokinetic studies of etoposide, including absorption, distribution, protein binding, metabolism and elimination. Dosage reduction is generally useful to avoid haematological toxicity in patients with renal dysfunction (creatinine clearance <50 mL/min). The need for dosage adjustment based on liver function in patients with liver dysfunction is not completely defined, but generally is not indicated in patients with minor liver dysfunction. Adaptive dosage adjustment based on individual pharmacokinetic parameters, estimated using limited sampling strategies and population pharmacokinetic models, is more appropriate. This approach has been used with success in different clinical trials to increase the etoposide dosage, without significantly increasing toxicity. Various pharmacodynamic models have been proposed to guide etoposide oral dosage. However, they lack precision and accuracy and need to be refined by considering other predictor variables in order to extend their application in current clinical practice.

Randomized cross-over clinical trial to study potential pharmacokinetic interactions between cisplatin or carboplatin and etoposide

AIMS

Cisplatin and carboplatin are often used in combination with etoposide. In a randomized cross-over study, the potential interaction between the two platinum drugs and the metabolism of etoposide was explored. In vitro investigations using human liver microsomes were also performed.

METHODS

Etoposide was administered to 15 patients over 3 days, with the platinum drug administered on day 2. The alternate platinum drug was administered on the second course. The pharmacokinetics of etoposide were determined on all 3 days of each cycle. The effect of platinum drugs on etoposide metabolism by human liver enzymes was explored in vitro.

RESULTS

Neither cisplatin nor carboplatin coadministration affected the pharmacokinetics of etoposide during cycle 1. When carboplatin was administered on course 2, etoposide AUC was 8% higher on day 2 compared with day 1 or day 3 (for day 2 vs day 3, 95% CI: -0.72, -0.08 mg ml(-1) min). In contrast, cisplatin on course 2 increased the AUC of etoposide (28%) on day 3 (day 3 vs day 1, 95% CI: 0.67, 2.09 mg ml(-1) min), with no effect on day 2. In vitro carboplatin and cisplatin (10-100 microm) inhibited the metabolism of etoposide, if rat liver microsomes were preincubated (30 min) with NADPH and the platinum complexes. With human liver microsomes a small effect on etoposide metabolism, but not on catechol formation, was observed.

CONCLUSIONS

The interaction between etoposide and platinum drugs is small and, given the pharmacokinetic variability seen with etoposide, the clinical impact is unlikely to be significant.

A phase I clinical and pharmacologic study of a carboplatin and irinotecan regimen combined with recombinant human granulocyte-colony stimulating factor in the treatment of patients with advanced nonsmall cell lung carcinoma

BACKGROUND

This Phase I study was designed to determine the toxicity and efficacy of a carboplatin and irinotecan (CPT-11) regimen with recombinant human granulocyte colony-stimulating factor (rhG-CSF) support for patients with advanced nonsmall cell lung carcinoma.

METHODS

Treatment consisted of carboplatin administered intravenously (i.v.) on Day 1 plus CPT-11 i.v. on Days 1, 8, and 15. The carboplatin dose was calculated using Calvert's formula, where the target area under the plasma concentration versus the time curve (AUC) was 5 or 6 mg x min/mL. rhG-CSF (2 microg/kg) was administered daily, except on Days 1, 8, and 15, until the leukocyte count exceeded 20,000/mm3 (10,000/mm3 after Day 16). Cycles were repeated every 4 weeks. Groups entered the trial at escalating CPT-11 and carboplatin dose levels of 60 mg/m2 and 5 mg x min/mL, 70/5 and 60/6.

RESULTS

Twenty-one patients were enrolled in this study, of whom 20 were assessable for toxicity and therapeutic efficacy. Two of 6 patients experienced Grade 4 diarrhea at the 70/5 dose level, suggesting that this was the maximum tolerated dose (MTD). However, the 60/6 dose level was included because toxicities were very mild at the 60/5 dose level. At the 60/6 dose level, 1 of 6 patients experienced severe, life-threatening toxicity. Therefore, subsequent dose escalation was stopped and the study terminated. There were 7 responses (35%) among the 20 patients. At the 60/6 dose level (n=5), the observed carboplatin AUC after aiming for a target AUC of 6 was 5.9+/-0.9 mg x min/mL, as expected, although the AUCs of both CPT-11 and its active metabolite, SN-38, were lower than expected.

CONCLUSIONS

The recommended doses for Phase II studies are 60 mg/m2 of CPT-11 and a target AUC of 5 mg x min/mL for carboplatin, plus rhG-CSF. The combination of AUC-based carboplatin and CPT-11 with rhG-CSF support appears to be an active regimen in the treatment of patients with NSCLC.

Evaluation of synergism by a novel three-dimensional model for the combined action of cisplatin and etoposide on the growth of a human small-cell lung-cancer cell line, SBC-3

Although the combination of cisplatin and etoposide has been used as standard therapy for small-cell lung cancer, it is difficult to demonstrate combination effects between cisplatin and etoposide in vitro. We therefore adopted a 3-dimensional (3-D) model to analyze the combination effects of anticancer drugs, and compared the results of analysis by the new 3-D model with those obtained from traditional 2-D models for the cisplatin-etoposide combination. In this study, using a human small-cell lung-cancer cell line (SBC-3), 3-D model analysis clearly identified a relationship depending on the concentrations of both drugs, and demonstrated that peak synergy occurred at the higher concentrations of cisplatin and etoposide. Antagonistic interactions were noted with a nadir at low concentrations of etoposide and cisplatin. In contrast, 2-D models such as combination index and isobologam analysis fail to characterize the complex interactions between cisplatin and etoposide, since their joint effects are concentration-dependent. Combination index (CI) plots show that synergy is evident only for molar ratios of cisplatin: etoposide of 2:1 to 1:5. On isobologram analysis, synergy could be detected when great inhibitory effects on cell growth were present (high endpoint), but not with small inhibitory effects (lower endpoints). Thus, either synergy or antagonism may occur, but depend on the selection of variables, such as the molar ratios or the endpoints chosen for the experiments. This could explain the inconsistency in the in vitro combination effects reported to date. The 3-D model, which compensates for the above deficiencies of 2-D models, can facilitate rigorous analysis of drug interactions over the entire clinical dose range, using microcomputers and sophisticated graphics programs. This direct and pragmatic method offers investigators a practical new tool with which to analyze drug combinations for cancer chemotherapy.

Carboplatin and cisplatin pharmacokinetics after intrapleural combination treatment in patients with malignant pleural effusion

BACKGROUND

Cisplatin (DDP) and carboplatin (CBDCA) are two of the most effective drugs in a locoregional approach. Since simultaneous combined treatment with intrapleural DDP and CBDCA has not been reported in humans, we investigated its use in patients with malignant effusions, focusing on pharmacokinetics.

PATIENTS AND METHODS

The pharmacokinetics of DDP and CBDCA were studied in 10 patients with malignant pleural effusion treated intrapleurally with a combination of DDP (60 mg/m2) and CBDCA (270 mg/m2) and in additional patients who received the same doses of drugs administered intravenously as single agents or in combination. Platinum (Pt) species originating from DDP (metabolites plus unchanged DDP) and intact CBDCA in plasma and pleural fluid ultrafiltrates were measured by means of high performance liquid chromatography and atomic absorption spectrometry.

RESULTS

Both in the plasma and pleural fluid, the total levels of free Pt represented the additive result of the individual concentrations of CBDCA and Pt-species derived from DDP. After intrapleural combination, high pleural-plasma ratios of the peak concentrations and AUCs were observed both for CBDCA and DDP-derived Pt species, highlighting a distinct local pharmacological advantage. However, the Pt species originating from DDP were absorbed more rapidly from the pleural cavity than CBDCA (Ka = 86 x 10(-3) vs. 37 x 10(-3) min-1, P < 0.05). Intrapleural combination of CBDCA and DDP produced therapeutic plasma levels of reactive (free) DDP species and increased the extent of their residence time (MRT) compared with single intravenous DDP treatment [peak concentration: 1.1 +/- 0.1 (SD) vs. 1.6 +/- 0.2 microgram/ml; MRT: 5.2 +/- 1.9 vs. 0.5 +/- 0.06 h]. Furthermore, the plasma AUC of free CBDCA after intrapleural combined treatment (2.1 +/- 0.5 mg/ ml x min) was similar to that after intravenous administration of CBDCA alone (2.1 +/- 0.2 mg/ml x min). The intrapleural treatment was well tolerated by all patients. Toxicity consisted of mild nausea and vomiting (grade 1-2 according to the WHO scale) in four patients. Myelosuppression (grade 1-2) was remarkable only in two heavily pretreated patients. No evidence of recurrence of the pleural effusion was observed in six patients (complete response), while an asymptomatic minimal fluid reaccumulation not requiring drainage (partial response) was observed in four patients.

CONCLUSIONS

The pharmacologic results seem to exclude a pharmacokinetic interaction between CBDCA and DDP and suggest that a dose of CBDCA 2-fold higher than that used in this study associated intrapleurally with 60 mg/m2 DDP could induce an acceptable and predictable myelosuppression.

Concurrent daily carboplatin and accelerated hyperfractionated thoracic radiotherapy in locally advanced nonsmall cell lung cancer

PURPOSE

This study was designed to evaluate the feasibility and efficacy of accelerated hyperfractionated thoracic radiotherapy concurrently combined with daily carboplatin in patients with locally advanced, unresectable nonsmall cell lung cancer.

METHODS AND MATERIALS

Thirty-one patients with locally advanced nonsmall cell lung cancer were treated with continuous course, twice daily thoracic radiotherapy (1.5 Gy each) to a total of 60 Gy over 4 weeks. Carboplatin (25 mg/m2) i.v. was given immediately before each morning thoracic radiotherapy. Blood samples were taken to measure the blood free platinum pharmacokinetics on day 1.

RESULTS

All 31 patients completed the protocol treatment without delay. The median age was 73 years, and the majority had Stage IIIA (32%) or IIIB (48%) disease. Major acute toxicity (> or = Grade 3) included 17 patients (55%) with leukopenia, 5 patients (16%) with thrombocytopenia, and 7 patients (23%) with esophagitis. One possible treatment-related death due to diffuse pneumonitis was observed. There were three complete responses (CRs) and 23 partial responses (PRs) in the radiation field, for a response rate of 84%. The relapse pattern was predominantly loco-regional, and the median survival time was 9.8 months. The area under the plasma level-time curve (AUC) of free platinum correlated significantly (r = -0.41, p = 0.04) with the surviving fraction of leukocytes, but not with the severity of the esophagitis. Responders had significantly (p = 0.04 by Welch's t-test) higher AUCs than nonresponders.

CONCLUSIONS

This combination therapy was feasible and efficacious against locally advanced nonsmall cell lung cancer. Although long-term local control still remains unsatisfactory, pharmacokinetic data are suggestive of a role for platinum in enhancing the radiation effect.

A single-sample assay for the estimation of the area under the free carboplatin plasma concentration versus time curve

The aim of this study was to develop and validate a simple and rapid method for the estimation of the area under the free carboplatin plasma concentration versus time curve (AUC). The relationship between the carboplatin AUC and the total plasma platinum (Pt) concentration 24 h after treatment was studied using data from 49 patients treated with 20-1600 mg/m2 carboplatin as a 60-100 min infusion (median 60 min). The relationship was confirmed by the in vitro incubation of carboplatin in human plasma and prospectively validated in 13 ovarian cancer patients. Free carboplatin was separated by ultrafiltration (MW cut off 30,000), and free and total Pt measured by atomic absorption spectrophotometry. There was a linear relationship in vivo between the 24 h (median 24.4; range 16.3-27.3 h) total plasma Pt concentration (microM) and free carboplatin AUC (mg/ml.min): AUC=(24 h Pt+0.3)/0.82 (r2=0.93, AUC median 5.8 (0.13-28)mg/ml.min, 24h Pt median 4.4 (0.1-23) microM). A similar relationship was observed in vitro [AUC =(24h Pt +0.1)/0.93 (r2=0.98, AUC median 7.9 (2.0-17) mg/ml.min, 24 h Pt median 7.1 (1.8-15) microM)]. The relationship derived from the in vivo data gave an unbiased and reasonably accurate estimate of the measured carboplatin AUC in 13 patients (AUC =5.1-8.7 mg/ml.min, GFR=59-129 ml/min, infusion time 30-45 min, 24 h sampling time 22.9-24.5 h), giving a percentage mean error of -4.2% and root mean squared percentage error of 11.5%. These results show that the analysis of a single blood sample taken 24 h after carboplatin administration can be used to produce an unbiased and reasonably accurate measure of the free carboplatin AUC. Unlike published limited sampling strategies, this method is not complicated by the need to accurately control the duration of the carboplatin infusion or the time at which the sample is taken.

Pharmacokinetically guided dosing of carboplatin and etoposide during peritoneal dialysis and haemodialysis

Two patients with relapsed Wilms' tumour and renal failure requiring dialysis were given carboplatin and etoposide by pharmacokinetically guided dosing. The target area under the drug plasma concentration vs time curve (AUC) was 6 mg ml-1 min for carboplatin and 18 and 21 mg ml-1 min for etoposide. On course 1 measured AUCs of carboplatin and etoposide were 6 and 20 mg ml-1 min for patient 1 and 6 and 21 mg ml-1 min for patient 2 respectively. Peritoneal dialysis did not remove carboplatin or etoposide from the plasma, however carboplatin but not etoposide was cleared by haemodialysis. Therapy with carboplatin and etoposide is possible in children and adults with renal failure who require dialysis, but in this situation pharmacokinetic monitoring is essential.

Phase I and pharmacokinetic study of a water-soluble etoposide prodrug, etoposide phosphate (BMY-40481)

Etoposide phosphate is a water-soluble prodrug of etoposide. A phase I and pharmacokinetic study has been performed over the dose range 25-110 mg/m2/day for 5 days (etoposide equivalent doses). The maximum tolerated dose (MTD) was 110 mg/m2/day for 5 days every 3 weeks and the dose-limiting toxicity was neutropenia. Other toxicities were mild, with the exception of 2 patients who displayed significant hypersensitivity reactions. The etoposide phosphate:etoposide area under the plasma concentration versus time curve (AUC) ratio was < 1% and the pharmacokinetic parameters for etoposide were within previously reported ranges. Pharmacodynamic analyses demonstrated that etoposide AUC and baseline white blood cell count were significant determinants of leucopenia (model r2 = 0.51).

The use of the Calvert formula to determine the optimal carboplatin dosage

Carboplatin is a chemotherapeutic agent frequently used in the treatment of various malignancies. The myelotoxicity and clinical efficacy of carboplatin correlate with the clearance of the drug, which is correlated to the glomerular filtration rate (GFR). Dosing of this agent based solely upon the patients body surface area is therefore not accurate enough; the GFR, and thus the clearance of carboplatin differ in each patient irrespective of the body area. Consequently, some patients undergo a higher systemic exposure, expressed as the area under the plasma concentration/time curve (AUC), than others when dosages of carboplatin are given on the basis of the body surface area. A high AUC correlates with increased toxicity, thus increasing the risks of the treatment, but in the case of a low AUC the therapeutical efficacy decreases. This indicates that an individual dosing strategy is warranted to obtain the optimal AUC. In this article, the development and application of a simple equation, known as the Calvert formula, are discussed. This formula can be used to calculate the carboplatin dose accurately in order to obtain a target AUC by using only the GFR. The formula is: dose (mg) = AUC (mg ml-1 min) x [GFR (ml/min) + 25 (ml/min)]. This formula has proven to be, in both retrospective and prospective studies, a reliable tool to calculate the optimal dose of carboplatin Future studies should determine the value of the creatinine clearance as a measure for the GFR.

Phase I study and clinical pharmacological evaluation of daily oral etoposide combined with carboplatin in patients with lung cancer

Twenty-eight patients with inoperable or relapsed lung cancer were given a combination of oral etoposide, administered once a day at doses ranging from 40 to 60 mg/m2/day (d) for 21 consecutive days, and carboplatin, administered intravenously over 1 h at doses ranging from 300 to 400 mg/m2 on day 1 to determine the appropriate doses of this combination. In addition, pharmacokinetic and pharmacodynamic analyses were performed. All the patients had a performance status of 0 to 1. Serum etoposide and free platinum (Pt) concentrations were measured using high-performance liquid chromatography and atomic absorption, respectively. Myelosuppression, nausea and vomiting were the dose-limiting toxicities of this schedule. The maximum tolerated dose (MTD) was 50 mg/m2/d oral etoposide for 21 days and 400 mg/m2 i.v. carboplatin on day 1. For heavily pretreated patients, the MTD was 40 mg/m2/d oral etoposide for 21 days and 350 mg/m2 i.v. carboplatin on day 1. No cumulative increase in the area under the concentration-time curve (AUC) for oral etoposide over time was observed. There were significant correlations between the free Pt serum level (6, 8, 12, 24 h post-dose) and etoposide AUC level (days 1, 10 and 21) for graded hematological toxicity, and the percentage decreases and nadir counts of hemoglobin, leukocytes, neutrophils and platelets. Several pharmacodynamic models were developed to predict the hematological toxicity. In order to facilitate pharmacodynamic evaluations in future studies, a limited sampling model for oral etoposide was also developed and validated.

Clinical pharmacokinetics of carboplatin in children

The present study was undertaken to evaluate in children the plasma pharmacokinetics of free carboplatin given at different doses and schedules and to evaluate the inter- and intrapatient variability and the possible influence of schedule on drug exposure. A total of 35 children (age range, 1-17 years) with malignant tumors were studied. All patients had normal renal function (creatinine clearance corrected for surface body area, above 70 ml min-1 m-2; range, 71-151 ml min-1 m-2) and none had renal involvement by malignancy. Carboplatin was given at the following doses and schedules: 175, 400, 500, and 600 mg/m2 given as as a 1-h infusion; 1,200 mg/m2 divided into equal doses and infused over 1 h on 2 consecutive days; and 875 and 1,200 mg/m2 given as a 5-day continuous infusion. A total of 57 courses were studied. Carboplatin levels in plasma ultrafiltrate (UF) samples were measured both by high-performance liquid chromatography and by atomic absorption spectrophotometry. Following a 1-h infusion, carboplatin free plasma levels decayed biphasically; the disappearance half-lives, total body clearance, and apparent volume of distribution were similar for different doses. In children with normal renal function as defined by creatinemia and blood urea nitrogen (BUN) and creatinine clearance, we found at each dose studied a limited interpatient variability of the peak plasma concentration (Cmax) and the area under the concentration-time curve (AUC) and a linear correlation between the dose and both Cmax (r = 0.95) and AUC (r = 0.97). The mean value +/- SD for the dose-normalized AUC was 13 +/- 2 min m2 l-1 (n = 57).2+ The administration schedule does not seem to influence drug exposure, since prolonged i.v. infusion or bolus administration of 1,200 mg/m2 achieved a similar AUC (13.78 +/- 2.90 and 15.05 +/- 1.44 mg ml-1 min, respectively). In the nine children studied during subsequent courses a limited interpatient variability was observed and no correlation (r = 0.035) was found between AUC and subsequent courses by a multivariate analysis of dose, AUC, and course number. The pharmacokinetic parameters were similar to those previously reported in adults; however, a weak correlation (r = 0.52, P = 0.03) between carboplatin total body clearance and creatinine clearance varying within the normal range was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro and in vivo effects of cisplatin and etoposide in combination on small cell lung cancer cell lines

The effects of cisplatin (CDDP) and etoposide (ETP) in combination were evaluated in vitro and in vivo using small cell lung cancer cell lines. The combination effects in vitro were investigated using isobologram analysis. Used together, CDDP and ETP showed a synergistic effect against cell growth on only 1 cell line (SBC-3), additive effects on 6 (SBC-2, SBC-5, Lu130, Lu134AH, Lu135T and H69) and an antagonistic effect on 1 (SBC-1). In the in vivo experiment, nude mice were inoculated with SBC-1, SBC-3 and SBC-5 cells. Two or 5 mg/kg CDDP and 10 or 30 mg/kg ETP were administered intraperitoneally alone and simultaneously in combination to nude mice. The in vivo effects of the combination were determined by comparing the observed growth ratio in mice treated with the combination with the expected value of this ratio calculated based on the assumption that the effects of the drugs were simply additive. According to this definition, synergistic effects were observed against all 3 tumors. Thus, the in vivo and in vitro effects differed. The toxicity of the combination therapy, which was analyzed by estimating the body weight change of mice, was no higher than that of CDDP or ETP alone. These results suggest that the excellent clinical effects of CDDP and ETP combination therapy may be attributable not to drug interaction at the cellular level but to the feasibility of combined use of them at full doses without overlapping side effects.

Long-term oral etoposide in metastatic breast cancer: clinical and pharmacokinetic results

To evaluate the activity of long-term, single-agent oral etoposide against advanced breast cancer, this study employed etoposide 50 mg/day and 100 mg/day (given over 14 days) in previously treated and chemotherapy-naive patients with histologically confirmed, recurrent or metastatic breast cancer. Of 38 patients, 24 had had chemotherapy, 34 had prior radiotherapy, and 31 had received hormone therapy. Etoposide courses in both treatment groups were repeated every 4 weeks for at least two courses; delays were instituted when patients' total leukocyte nadir fell to or below 3.0 x 10(9)/l. Dose reductions were made in the 100-mg group (to 50 mg/day) if World Health Organization leukopenia grade 3 or higher was present. Plasma pharmacokinetic profiles were measured in selected patients to assess inter- and intrapatient variability in etoposide's oral bioavailability. No complete responses were achieved among the 36 patients evaluable for response, but eight patients had a partial response. Responses were more frequent at the 100-mg dose and in previously untreated patients (seven of eight partial responders had not had previous chemotherapy). Median duration of response was 16 weeks (range, 7 to 46). Myelosuppression (variable and unpredictable) and alopecia (universal) were the notable toxicities. Pharmacokinetic analyses of oral bioavailability revealed significant interpatient variability, but much less intrapatient variability when successive etoposide courses in individual patients were evaluated. Despite the relatively small number of patients in this study, the responses achieved by previously untreated patients suggest etoposide's value against breast cancer. Further trials should use pharmacokinetic studies to assess bioavailability as well as to help define 'target' etoposide doses, based on plasma etoposide levels, during treatment.

Pharmacokinetics of etoposide: correlation of pharmacokinetic parameters with clinical conditions

The pharmacokinetic parameters of etoposide were established in 35 patients receiving the drug parenterally within the framework of different polychemotherapy protocols. A total of 62 data for 24-h kinetics were analysed. After sample extraction and high-performance liquid chromatography (HPLC) or thin-layer chromatographic (TLC) separation, etoposide was measured by means of [252Cf]-plasma desorption mass spectrometry (PDMS). This highly specific detection system proved to be very practicable and reproducible. The present study comprised two parts that were absolutely comparable in terms of clinical and pharmacokinetic parameters. In part II of the study, sensitivity was improved by modifying the analytical technique. After the exclusion of patients who had previously been given cisplatin or who exhibited renal impairment and of one patient who showed extremely high levels of alkaline phosphatase, gamma-GT and SGPT, the mean values calculated for the pharmacokinetic parameters evaluated were: beta-elimination half-life (t 1/2 beta), 4.9 +/- 1.2 h; mean residence time (MRT), 6.7 +/- 1.4 h; area under the concentration-time curve (AUC), 5.43 +/- 1.74 mg min ml-1; volume of distribution at steady state (Vdss), 6.8 +/- 2.7 l/m2; and clearance (Cl), 18.8 +/- 5.3 ml min-1 m-2. The pharmacokinetic parameters were correlated with 12 different demographic or biochemical conditions. Impaired renal function, previous application of cisplatin and the age of patients were found to influence etoposide disposition to a statistically significant extent. We suggest that the dose of etoposide should be reduced in elderly patients and/or in individuals with impaired renal function, especially in those exhibiting general risk factors such as reduced liver function with regard to the polychemotherapy.

High failure rate of carboplatin-etoposide combination in good risk non-seminomatous germ cell tumours

24 patients with good risk non-seminomatous germ cell tumours (GR-NSGCT) were enrolled in a phase II trial combining carboplatin (C) and etoposide (E). Carboplatin was given at a fixed dose of 450 mg/m2 at d2, and E 120 mg/m2, dl-3, every 4 weeks x 4 cycles (cy). Myelosuppression was the major toxicity with neutropenia grade 4 in 18 cy (19%) and grade 3 in 26 cy (27%). Thrombocytopenia grade 3 and 4 occurred in 7 and 1 cy, respectively. Responses included: 20 complete responses (CR) (83%) with 16 clinical CR and 4 pathological CR; 3 additional patients had complete surgical removal of residual disease (SRRD) with viable tumour (surgical CR); 1 patient progressed during C+E therapy. 5 of the 16 clinical CR relapsed, and all the 3 surgical CR progressed despite post-operative salvage chemotherapy. Adverse events occurred in 9 patients (37.5%; 95% C.I., 19-59%). After a median follow-up of 24 m (range 14 to 38) 4 patients had died [3 progressive disease (PD), 1 suicide while in CR], 3 were alive with PD, and 17 had no evidence of disease. No significant correlation between area under the curve values of carboplatin, overall treatment failure and the platelet nadirs was observed. We conclude that the efficacy of the C+E regimen as given in our protocol is inferior to the standard cisplatin-containing regimens. The low dose-density (D/I) of carboplatin could be responsible for the high failure rate.

The optimisation of carboplatin dose in carboplatin, etoposide and bleomycin combination chemotherapy for good prognosis metastatic nonseminomatous germ cell tumours of the testis

An analysis of carboplatin dose response was performed in 121 patients with good prognosis metastatic nonseminomatous germ cell tumours (NSGCT) of the testis, referred to the Royal Marsden Hospital since 1984, who had been given combination carboplatin, etoposide and bleomycin (CEB) chemotherapy. With a median follow-up of 40 months (range: 7 to 85 months) nine patients (7%) have failed CEB. Carboplatin dose was analysed in all patients using body surface area (BSA) to derive a carboplatin dose per metre squared (mg/m2) and by calculation of a predicted serum concentration chi time (AUC: area under the curve) derived from the glomerular filtration rate (GFR), using the formula; Dose = AUC(GFR + 25). At a carboplatin dose of 400 mg/m2 or greater 2 out of 58 patients (3.4%) failed treatment while 7 out of 63 patients (11%) who received a dose less than this failed (p greater than 0.1). At an AUC of 5.0 mg.min/ml or greater, 2 out of 74 patients (2.7%) failed while 7 out of 47 patients (14.9%) who had an AUC less than this failed (p less than 0.05). There was evidence for a dose/response relationship at relatively low doses and the failure rate rose to 26% for doses less than 4.5 mg.min/ml (p less than 0.001) or 15.6% for doses less than 350 mg/m2 (p greater than 0.1). In view of the more precise determination of toxicity and efficacy it is recommended that carboplatin dose be based on the GFR.

Pharmacokinetics of high-dose etoposide after short-term infusion

The pharmacokinetics of high-dose etoposide (total dose, 2100 mg/m2 divided into three doses given as 30-min infusions on 3 consecutive days) were studied in ten patients receiving high-dose combination chemotherapy followed by autologous bone marrow transplantation. In addition to etoposide, all subjects received 2 x 60 mg/kg cyclophosphamide and either 6 x 1,000 mg/m2 cytosine arabinoside (ara-C), 300 mg/m2 carmustine (BCNU), or 1,200 mg/m2 carboplatin. Plasma etoposide concentrations were determined by 252Cf plasma desorption mass spectrometry. In all, 27 measurements of kinetics in 10 patients were analyzed. According to graphic analysis, the plasma concentration versus time data for all postinfusion plasma etoposide values were fitted to a biexponential equation. The mean values for the calculated pharmacokinetic parameters were: t1/2 beta, 256 +/- 38 min; mean residence time (MRT), 346 +/- 47 min; AUC, 4,972 +/- 629 micrograms min ml-1 (normalized to a dose of 100 mg/m2); volume of distribution at steady state (Vdss), 6.6 +/- 1.2 l/m2; and clearance (CL), 20.4 +/- 2.4 ml min-1 m-2. A comparison of these values with standard-dose etoposide pharmacokinetics revealed that the distribution and elimination processes were not influenced by the dose over the range tested (70-700 mg/m2). Also, the coadministration of carboplatin did not lead to significant pharmacokinetic alterations. Although plasma etoposide concentrations at the time of bone marrow reinfusion (generally at 30 h after the last etoposide infusion) ranged between 0.57 and 2.39 micrograms/ml, all patients exhibited undelayed hematopoietic reconstitution.

Comparison of the cytotoxic activities of cisplatin and carboplatin against glioma cell lines at pharmacologically relevant drug exposures

Carboplatin has lower nephro- and neurotoxicities and better penetration into brain tissue than cisplatin. If carboplatin has comparable cytotoxicity against glioma cells, it might have a therapeutic advantage in the treatment of malignant gliomas. Using an assay of colony-forming efficiency, we compared the cytotoxicity of these two drugs in human glioma cell lines SF-126, SF-188, U87-MG, and U251-MG. The experiments were designed so that the product of in vitro drug concentration (C) and time (T) would encompass the same range of values as the C x T of the ultrafilterable platinum plasma fraction as determined by pharmacokinetic studies in man. The in vitro stability of the drugs was evaluated by measuring the cytotoxicity of aged drugs with a microculture tetrazolium assay. Cisplatin and carboplatin were both stable during the 2-h treatment. The cytotoxic activities of these drugs at clinically achievable levels of drug exposure were of the same order of magnitude. These results, in conjunction with the lower nephro- and neurotoxicities of carboplatin, the higher platinum levels in brain tissue after treatment with carboplatin, and the encouraging results of carboplatin in the clinical treatment of brain tumors that have been demonstrated in other studies, suggest that carboplatin might be preferable to cisplatin in the treatment of patients with malignant glioma.

Carboplatin-based chemotherapy with pharmacokinetic analysis for patients with hemodialysis-dependent renal insufficiency

Three patients with renal insufficiency requiring hemodialysis were treated with carboplatin at 100 mg/m2 in combination with etoposide for advanced germ-cell tumor (GCT, two cases) or Adriamycin + vinblastine for a transitional-cell carcinoma of the ureter (one case). Hemodialysis was performed 24 h after the administration of carboplatin. Both patients with GCT achieved a complete response, and the patient with transitional-cell carcinoma of the ureter was inevaluable for response but his disease has not progressed. The dose of carboplatin was increased in one patient as renal function improved on therapy. In two patients, the pharmacokinetics of carboplatin were determined; the pre-dialysis half-lives, AUC, and total body clearances of free carboplatin-derived platinum were estimated to be 32 and 18.3 h, 4.93 and 6.17 mg ml-1 min, and 18.2 and 18.7 ml/min, respectively. The dialysis elimination half-lives (t1/2 beta) of 2 and 3 h, respectively, for these two patients were markedly lower than the predialysis values, indicating that carboplatin was dialyzed. In summary, carboplatin can be given to patients with severe renal insufficiency. Adequate AUCs were achieved and dialysis limited systemic exposure to free carboplatin.