L. J. C. van Warmerdam

Pharmacokinetics of paclitaxel and carboplatin in a dose-escalating and dose-sequencing study in patients with non-small-cell lung cancer. The European Cancer Centre.

PURPOSE To investigate the pharmacokinetics and pharmacodynamics of paclitaxel (P) and carboplatin (C) in a sequence-finding and dose-escalating study in untreated non-small-cell lung cancer (NSCLC) patients. PATIENTS AND METHODS Fifty-five chemotherapy-naive patients with NSCLC were entered onto the pharmacokinetic part of a large phase I trial in which P was administered as a 3-hour infusion at dosages of 100 to 250 mg/m2, and C over 30 minutes at dosages of 300 to 400 mg/m2. Patients were randomized for the sequence of administration, first C followed by P or vice versa. Each patient received the alternate sequence during the second and subsequent courses. RESULTS The most important hematologic toxicity encountered-was neutropenia. Hematologic toxicity was not dependent on the sequence in which P and C were administered, but there was cumulative neutropenia. Nonhematologic toxicities consisted mainly of vomiting, myalgia, and arthralgia. No sequence-dependent pharmacokinetic interactions for the P area under the concentration-time curve (P-AUC), maximal plasma concentration (P-Cmax), or time above a threshold concentration of 0.1 mumol/L (P-T > or = 0.1 mumol/L) were observed. However, there was a significant difference for the metabolite 6 alpha-hydroxypaclitaxel AUC (6OHP-AUC). Higher 6OHP-AUCs were observed when C was administered before P. The mean plasma ultrafiltrate AUC of C (CpUF-AUC) at the dosage of 300 mg/m2 for the sequence C-->P was 3.52 mg/mL.min (range, 1.94 to 5.83) and 3.62 mg/mL.min for the sequence P-->C (range, 1.91 to 5.01), which is not significantly different (P = .55). Of 45 assessable patients, there were five major responders (three complete responders and two partial responders). Four of five responses occurred at dosages above dose level 4 (P 175 mg/m2 + C 300 mg/m2). The median survival duration was best correlated with the P dose (4.8 months for doses < 175 mg/m2 v 7.9 months for doses > or = 175 mg/m2, P = .07; P-T > or = 0.1 mumol/L, 4.8 months for < 15 hours v 8.2 months for > or = 15 hours, P = .06). CONCLUSION There was no pharmacokinetic-sequence interaction between C and P in this study. A clear dose-response relation with respect to response rate and survival was observed. The pharmacokinetic parameter P-T > or = 0.1 mumol/L was related to improved survival in this study.

Phase I and pharmacologic study of the combination paclitaxel and carboplatin as first-line chemotherapy in stage III and IV ovarian cancer.

PURPOSE To determine the maximum-tolerated dose for the combination paclitaxel and carboplatin administered every 4 weeks and to gain more insight into the pharmacokinetics and pharmacodynamics of this combination in previously untreated ovarian cancer patients. PATIENTS AND METHODS Thirty-five chemotherapy-naive patients with suboptimally debulked stage III (tumor masses > 3 cm) and stage IV ovarian cancer were entered onto this phase I trial in which paclitaxel was administered as a 3-hour intravenous (IV) infusion at dosages of 125 to 225 mg/m2 immediately followed by carboplatin over 30 minutes at dosages of 300 to 600 mg/m2. A total of six courses was planned, followed by a second-look laparoscopy/laparotomy. Patients with a response and/or minimal residual disease at second-look laparoscopy received three additional courses. Twenty-six patients participated in the pharmacokinetic part of the study. RESULTS The most important hematologic toxicity encountered was neutropenia. Neutropenia was more pronounced for the higher dose levels (DLs) and was cumulative. Thrombocytopenia was mild in the first eight DLs, but increased during the treatment courses. Nonhematologic toxicities consisted mainly of vomiting, neuropathy, fatigue, rash, pruritus, myalgia, and arthralgia. Dose-limiting toxicities (DLTs) in this trial were neutropenic fever, thrombocytopenia that required platelet transfusions, and cumulative neuropathy. Of 33 patients assessable for response, 26 major responders (78%, 20 complete response [CR] and six partial response [PR]) were documented. The maximal concentration (Cmax) of paclitaxel and the area under the concentration-time curve (AUC) were not different from the historical data for paclitaxel as a single agent. Retrospective analysis using a modified Calvert formula showed that the measured carboplatin AUCs in plasma ultrafiltrate (pUF) were 30% +/- 3.4% less than the calculated carboplatin AUC. Neutropenia was more pronounced than could be expected on the basis of the historical times above a threshold concentration greater than 0.1 mumol/L (T > or = 0.1 mumol/L) or 0.05 mumol/L (T > or = 0.05 mumol/L), and thrombocytopenia was less than could be expected from historical sigmoidal Emax models. CONCLUSION The combination of paclitaxel 200 mg/ m2 and carboplatin 550 mg/m2 every 4 weeks is a well-tolerated treatment modality. The paclitaxel-carboplatin combination is highly active in stage III (bulky) and stage IV ovarian cancer. No indications for a pharmacokinetic drug-drug interaction between carboplatin and paclitaxel were found.

Limited-sampling models for anticancer agents

Pharmacokinetic parameters of antineoplastic drugs are usually generated from concentration/time profiles obtained after multiple venipunctures. With limited-sampling models (LSM) this number can be reduced to between one and three timed plasma samples. LSMs may facilitate population pharmacokinetic/pharmacodynamic studies, which eventually may lead to a dosing strategy based on the characteristics of the individual patient. In this article, the development, validation and application of several LSMs reported in the literature are reviewed.

Phase I clinical and pharmacokinetic study of topotecan administered by a 24-hour continuous infusion.

PURPOSE To determine the maximum-tolerable dose (MTD) and to investigate the pharmacokinetics and pharmacodynamics of topotecan in a phase I study. Topotecan is a novel semisynthetic derivative of the anticancer agent camptothecin and inhibits the intranuclear enzyme topoisomerase I. Broad preclinical activity rationalized further clinical evaluation. PATIENTS AND METHODS In this phase I trial, topotecan was administered by 24-hour continuous infusion every 21 days to patients with solid malignant tumors. RESULTS A total of 25 eligible patients, of whom 22 were pretreated, entered the study. They received the following dosages of topotecan: 2.5, 3.75, 5.60, 8.4, and 10.5 mg/m2 by 24-hour infusion. Reversible leukopenia and thrombocytopenia were dose-limiting, with mild anemia occurring regularly. Other toxicities, such as alopecia, mucositis, nausea, and vomiting were sporadic and mild. Responses were not observed. However, eight patients had stable disease. The plasma concentration-time curves were not compatible with standard linear pharmacokinetic models, and indications were found for the occurrence of nonlinear (saturation) kinetics at the dosages studied. CONCLUSION The recommended dose for phase II studies is 8.4 mg/m2 when administered as a 24-hour infusion, which is well tolerated. Further studies will be necessary to account for the putative nonlinear behavior of the drug.

Pharmacokinetics and metabolism of docetaxel administered as a 1-h intravenous infusion.

Abstract Docetaxel, a taxane antitumor agent, was administered to 24 patients by a 1-h intravenous infusion at a dose level of 100 mg/m2 with pharmacokinetic monitoring. The plasma concentration-versus-time data were fitted with a three-compartment model. The mean area under the curve (AUC) for docetaxel was 3.1 ± 0.9 h · mg/l and the clearance was 34.8 ± 9.3 l/h per m2. There was considerable interpatient pharmacokinetic variability. In 33% of the patient population, metabolites were detected in plasma samples collected 5–30 min after the end of the infusion. The cyclized oxazolidinedione metabolite M4 was most frequently present and was detected in 8 out of 24 patients with maximal concentrations between 0.022 and 0.23 mg/l. Logistic regression analysis was performed to predict M4 docetaxel metabolism. In the final model, alanine aminotransferase and alkaline phosphatase levels were the strongest predictors. No relationship was found between M4 metabolism and percentage decrease in neutrophil count in this study. Three patients with high M4 concentrations in plasma during course 1 suffered from most pronounced fluid retention (grade 2–3) after two to five courses.

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)×[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.

Pharmacokinetics and pharmacodynamics of topotecan given on a daily-times-five schedule in phase II clinical trials using a limited-sampling procedure

Abstract Topotecan is a novel semisynthetic derivative of the anticancer agent camptothecin and inhibits the intranuclear enzyme topoisomerase I. The lactone structure of topotecan, which is in equilibrium with the inactive ring-opened hydroxy acid, is essential for this activity. We performed a pharmacokinetics study as part of phase II clinical trials in patients with various types of solid tumors, giving topotecan at 1.5 mg/m2 per day by 30-min infusion for 5 consecutive days, with courses being repeated every 3 weeks. Previously validated limited-sampling models, using concentration measurements in samples obtained 2 h after infusion, were used to calculate the area under the plasma concentration-time curves (AUCs) for both chemical forms. Samples were obtained from a total of 36 patients over 136 treatment days. The mean AUC of the closed-ring form (AUCclosed) was 8.74 (range 2.3–16.3)  μM min per day, and the mean AUC of the ring-opened form (AUCopen) was 11.5 (range 3.2–46.0)  μM min per day (interpatient variability 34–61%). In each patient the AUC values achieved on the 1st day of administration were similar to and, thus, predictive for those achieved during the following days, with a day-to-day variation of 7.39% being recorded for the AUCclosed and that of 12.6%, for the AUCopen. There was no drug accumulation during the 5 consecutive treatment days of each cycle. However, despite the large interpatient pharmacokinetic variability, the importance of regular drug monitoring on this schedule can be questioned, as the pharmacodynamic variability was relatively small.

Phase II study of the combination carboplatin and paclitaxel in patients with ovarian cancer

BACKGROUND Recently the feasibility of combining carboplatin with paclitaxel has been demonstrated in dose-finding studies. Maximum tolerated doses were 550 mg/m2 and 200 mg/m2 (three hours), respectively. We report now a phase II study in ovarian cancer patients. PATIENTS AND METHODS Twenty-one chemo-naïve patients with optimally (n = 6) or suboptimally (n = 15) debulked stage III or IV ovarian cancer were treated every three weeks for six courses with paclitaxel (200 mg/m2) as a three-hour infusion, immediately followed by carboplatin (550 mg/m2) as a 30-minute infusion. RESULTS Uncomplicated neutropenia was the principal toxicity, with mild anemia occurring regularly. As observed in the preceding phase I study, a relative lack of thrombocytopenia, generally grade III was found. Other toxicities consisted of mild neurotoxicity, nausea and vomiting, alopecia, myalgia, and bone pain. All suboptimally debulked patients responded to therapy. Overall, 12 patients underwent second-look laparoscopy, which revealed a pathologically confirmed complete remission in six. The median follow-up interval at the time of analysis was 14 months. Twelve patients are currently free of progression, at 8+ to 19 +/- months after the start of therapy. CONCLUSION The carboplatin/paclitaxel combination appears to be a well-tolerated regimen, yielding high response rates. This combination has now gone forward to be evaluated in prospective randomized trials versus the cisplatin/paclitaxel combination.

Limited Sampling Strategies for Investigating Paclitaxel Pharmacokinetics in Patients Receiving 175 mg/m2 as a 3-Hour Infusion

SummaryResults from a randomised European-Canadian trial showed that paclitaxel 175 mg/m2 infused as a 3-hour infusion is recommended in patients with platinum-refractory ovarian cancer. We assessed limited sampling models for relevant paclitaxel pharmacokinetic parameters using stepwise forward multiregression analysis for both area under the plasma concentration versus time curve from time 0 to 27 hours (AUC) and the time above a plasma threshold concentration of 0.1 µmol/L (T≥0.1 µmol/L) for the 3-hour infusion of 175 mg/m2. These strategies will be incorporated into future studies investigating pharmacokinetic/pharmacodynamic relationships of paclitaxel, using this dose and schedule. 24 pharmacokinetic curves were investigated from 24 patients with ovarian cancer treated with paclitaxel. 13 curves were selected by computer randomisation for the development of the model and the other 11 curves were used for the validation of the developed strategy. All patients received paclitaxel during a 3-hour infusion at a dosage of 175 mg/m2. Both pharmacokinetic parameters of interest, AUC and T≥0.1 µmol/L, could be predicted adequately with a 2-sample point model. This 2-point model, selected as optimal for the determination of the T≥0.1 µmol/L, was: