Multiple-dose pharmacokinetics of epirubicin at four different dose levels: studies in patients with metastatic breast cancer

RS7435335 located in the UGT2B7 gene may be a possible genetic marker for the clinical response and prognosis of breast cancer patients receiving neoadjuvant chemotherapy

OBJECTIVE

To evaluate the predictive efficacy and prognostic value of rs7435335 located in the UGT2B7 gene as a genetic marker in breast cancer patients receiving neoadjuvant chemotherapy (NAC).

METHODS

A total of 190 patients with breast cancer treated with NAC were enrolled to detect the rs7435335 SNP by sequenom. Miller-Payne grades were used to evaluate the treatment efficacy. The association between rs7435335 and chemotherapy efficacy and prognosis was analyzed.

RESULTS

Altogether, 42 cases (22.1%) achieved pathologic complete response (pCR). The results of the univariate analysis showed that rs7435335 had no statistically significant difference with pCR and Miller-Payne grades (P > 0.05). When grouping was done in accordance with the ER status, the pCR and Miller-Payne grades significantly associated with rs7435335 ( P < 0.05) only in the ER-negative group. Multivariate logistic regression analysis suggested that rs7435335 in the ER-negative group was an independent predictor of pCR ( P < 0.05). Survival analysis showed that the disease-free survival (DFS) time in patients with GA genotype was longer than that of GG genotype, and rs7435335 predicted the DFS in the ER-negative group.

CONCLUSION

The UGT2B7 rs7435335 is associated with the NAC efficacy and prognosis. Patients with GA genotype have better efficacy and prognosis. Rs7435335 was found to be a possible gene marker for pCR and prognosis in ER-negative patients who received NAC.

Pharmacokinetics of Selected Anticancer Drugs in Elderly Cancer Patients: Focus on Breast Cancer

Background: Elderly patients receiving anticancer drugs may have an increased risk to develop treatment-related toxicities compared to their younger peers. However, a potential pharmacokinetic (PK) basis for this increased risk has not consistently been established yet. Therefore, the objective of this study was to systematically review the influence of age on the PK of anticancer agents frequently administered to elderly breast cancer patients. Methods: A literature search was performed using the PubMed electronic database, Summary of Product Characteristics (SmPC) and available drug approval reviews, as published by EMA and FDA. Publications that describe age-related PK profiles of selected anticancer drugs against breast cancer, excluding endocrine compounds, were selected and included. Results: This review presents an overview of the available data that describe the influence of increasing age on the PK of selected anticancer drugs used for the treatment of breast cancer. Conclusions: Selected published data revealed differences in the effect and magnitude of increasing age on the PK of several anticancer drugs. There may be clinically-relevant, age-related PK differences for anthracyclines and platina agents. In the majority of cases, age is not a good surrogate marker for anticancer drug PK, and the physiological state of the individual patient may better be approached by looking at organ function, Charlson Comorbidity Score or geriatric functional assessment.

Impact of UGT2B7 His268Tyr polymorphism on the outcome of adjuvant epirubicin treatment in breast cancer

INTRODUCTION

Epirubicin is a common adjuvant treatment for breast cancer. It is mainly eliminated after glucuronidation through uridine diphosphate-glucuronosyltransferase 2B7 (UGT2B7). The present study aimed to describe the impact of the UGT2B7(His268Tyr) polymorphism on invasive disease-free survival in breast cancer patients after epirubicin treatment.

METHODS

This is a pharmacogenetic study based on samples collected from 745 breast cancer patients of the Austrian Tumor of breast tissue: Incidence, Genetics, and Environmental Risk factors (TIGER) cohort who did not present metastases at baseline. This cohort included 205 women with epirubicin-based combination chemotherapy, 113 patients having received chemotherapy without epirubicin and 427 patients having received no chemotherapy at all. Of the epirubicin-treated subgroup, 120 were subsequently treated with tamoxifen. For all women UGT2B7(His268Tyr) was genotyped. Invasive disease-free survival was assessed using Kaplan-Meier and Cox's proportional hazard regression analysis.

RESULTS

Among the 205 epirubicin-treated patients, carriers of two UGT2B7(268Tyr) alleles had a mean invasive disease-free survival of 8.6 (95% confidence interval (CI) 7.9 to 9.3) years as compared to 7.5 (95% CI 6.9 to 8.0) years in carriers of at least one UGT2B7(268His) allele (adjusted hazard ratio (HR) = 2.64 (95% CI 1.22 to 5.71); P = 0.014). In addition, the impact of the UGT2B7(His268Tyr) polymorphism became even more pronounced in patients subsequently treated with tamoxifen (adjusted HR = 5.22 (95% CI 1.67 to 26.04); P = 0.015) whereas no such difference in invasive disease-free survival was observed in patients not receiving epirubicin.

CONCLUSIONS

Breast cancer patients carrying the UGT2B7(268Tyr/Tyr) genotype may benefit most from adjuvant epirubicin-based chemotherapy. These results warrant confirmation in further studies.

Stability and in vivo evaluation of pullulan acetate as a drug nanocarrier

To develop pullulan acetate nanoparticles (PANs) as a drug nanocarrier, pullulan acetate (PA) was synthesized and characterized. Its acetylation degree determined by the proton nuclear magnetic resonance ((1)H NMR) was 2.6. PANs were prepared by the solvent diffusion method and characterized by transmission electron microscope (TEM), size distribution, and zeta potential techniques. PANs had nearly spherical shape with a size range of 200-450 nm and low zeta potentials both in distilled water and in 10% FBS. The storage stability of PANs was observed in distilled water. PANs were stored for at least 2 months with no significant size and zeta potential changes. The safety of PANs was studied through single dose toxicity test in mice, and the result showed that PANs were well tolerated at the dose of 200 mg/kg in mice. Epirubicin-loaded PANs (PA/EPI) were also prepared and characterized in this study. Moreover, the in vivo pharmacokinetics of PA/EPI was investigated. Compared with the free EPI group, the PA/EPI group exhibited higher plasma drug concentration, longer half-life time (t(1/2)) and the larger area under the curve (AUC). All results suggested that PANs were stable, safe, and showed a promising potential on improving the bioavailability of the loaded drug of the encapsulated drug.

Individually tailored toxicity-based 5-fluorouracil, epirubicin and cyclophosphamide (FEC) therapy of metastatic breast cancer

Chemotherapy dosing only based on body surface area (BSA) results in marked pharmacokinetic and toxicity variations, which may result in an inferior outcome for some patients. A toxicity-based dosing schedule for individually tailored treatment with granulocyte colony-stimulating factor (G-CSF) supported 5-fluorouracil (F), epirubicin (E) and cyclophosphamide (C) (dFEC) was developed and studied in patients with metastatic breast cancer with the purpose to determine its efficiency and toxicity. Twenty-six women, median age 48 years, were included and the individual E and C doses were tailored stepwise based on the recorded hematological toxicity. Twenty-one patients (81%; 95% confidence interval (CI), 66% to 96%) had an objective response, including six complete responses (23%; CI, 7%-39%). At median follow-up of 113 months, the median time to progression and median overall survival were 14 and 36 months, respectively. The delivered dose intensity was high but varied substantially between patients (ranges F 126-202, E 14.4-36.0, C 160-510 mg/m(2)/w). The dominating grade III/IV toxicity was nausea (12% of patients) and febrile neutropenia (31% of patients). The tailored and dose-escalated FEC was highly active and feasible in metastatic breast cancer and may provide a pragmatic way of overcoming the shortcomings of standard BSA-based dosing.

Pharmacokinetic/pharmacodynamic modelling in oncological drug development

For many oncological agents, myelosuppression is the dose-limiting toxicity and the quantitative characterisation of the relationship between drug dose, plasma concentration and haematological toxicity is of importance in the drug development. Mechanism-based population pharmacokinetic-pharmacodynamic models have been developed for this purpose and the applications of these in candidate selection, first-in-man studies, prodrug and formulation development, dose finding, schedule optimisation, assessing influence of modifying agents, drug combination studies, subgroup identification and feedback individualisation are reviewed.

Liver metastases from breast cancer: management of patients with significant liver dysfunction

The liver is a common site of metastases in breast cancer. Although the development of liver metastases has long been associated with a poor prognosis in this disease, this dogma has been challenged by more recent data, perhaps reflecting some treatment and other technological advances achieved in the last decade. Nevertheless, the specific population of breast cancer patients presenting with liver disease and associated liver dysfunction remain poorly studied. These women still seem to have a poor prognosis as compared to other patients with liver metastases. This is further complicated by the fact that the most active cytotoxic agents in breast cancer have significant hepatic metabolism and/or biliary excretion. Unfortunately, since these patients have been most of the time excluded from clinical trials, there are currently no clear recommendations for the management of such dramatic presentations. With some exceptions, recommendations for dose adjustments have also been largely empirical. In this paper, we review the optimal doses of cytotoxics used in this clinical situation and provide some tips on the management of these patients, based on the limited data currently available in the literature.

Maximum a posteriori Bayesian estimation of epirubicin clearance by limited sampling

AIMS

To develop a limited sampling strategy for estimation of epirubicin clearance.

METHODS

The data set comprised 1051 concentrations measured in 105 patients with advanced or metastatic breast cancer treated with epirubicin alone. Ten limited sampling designs comprising two or three blood samples were proposed, taken at times identified by D-optimality from population pharmacokinetic parameter estimates. The data set was then truncated to include the sampling times for each of the designs. MAP Bayesian estimates of clearance were generated for each design and compared with clearance estimates obtained using all the data. The limited sampling designs were also validated using a separate data set obtained from 18 patients with either breast cancer or hepatocellular carcinoma. The sensitivity of the best limited sampling designs to sample time recording errors of 0-10% or 10-20% was then assessed using a simulated data set including 200 patients.

RESULTS

The optimum sampling times were: end of the injection and 18 min, 40 min, 3 h, 10 h and 48 h after the start of the injection. The best three-sample design included samples at 40 min, 3 h and 48 h and gave unbiased estimates of clearance with an imprecision of 9.1% (95% CI 7.3, 10.5). The best two sample design included samples at 3 and 48 h and gave unbiased estimates of clearance with an imprecision of 12.4% (95% CI 9.6, 14.6). Using the validation data set, these two and three sample designs gave unbiased estimates of clearance with an imprecision of 5.6% (95% CI 3.7, 7.0) and 4.2% (95% CI 2.6, 5.3), respectively. Simulations that included 0-10% or 10-20% errors in the recording of the blood sampling times had negligible effects on the bias and imprecision of clearance estimates.

CONCLUSIONS

Limited sampling designs have been identified and validated that estimate epirubicin clearance with adequate precision and without bias from two or three blood samples. These designs also allow flexibility in blood sample collection and are robust with regard to sample time recording errors.

Pharmacokinetic-pharmacodynamic relationships of the anthracycline anticancer drugs

The anthracycline glycoside antibiotics represent a group of potent anticancer agents with a wide spectrum of activity against solid tumours and haematological malignancies, and are the mainstay of a large number of clinical protocols for the treatment of adult and childhood neoplastic diseases. Their clinical activity is limited, however, by acute and chronic adverse effects. Myelosuppression, predominantly neutropenia and leucopenia, is the dose-limiting toxicity; in addition to this, mucositis, nausea, vomiting and alopecia are frequent, whereas hepatopathy, characterised by elevated bilirubin concentrations, occurs less frequently. Cardiotoxicity is a major adverse effect of the anthracycline antibiotics and can be acute or chronic; in the acute setting, electrocardiographic abnormalities may be seen, including ST-T elevations and arrhythmias, but chronic cardiotoxicity represents a serious adverse effect that may be lethal due to the development of irreversible, cumulative dose-dependent, congestive cardiomyopathy. The occurrence of toxicity displays a marked interindividual variation, and for this reason the pharmacokinetics and pharmacodynamics of anthracyclines have been extensively investigated in order to identify integrated models that can be used in the clinical setting to prevent the development of serious toxicity, mainly leucopenia, and maximise tumour exposure. Pharmacokinetics has been recognised to influence both the toxicity and the activity of anthracyclines; in particular, there is increasing evidence that the mode of administration plays an important role for cumulative cardiotoxicity and data indicate that bolus administration, rather than continuous infusion, appears to be an important risk factor for anthracycline-induced cardiomyopathy, thus implying that this type of toxicity is maximum concentration-dependent. On the contrary, exposure to the drug, as measured by area under the curve, seems best related to the occurrence of leucopenia. Finally, the development of pharmacokinetic-pharmacodynamic models allows the simulation of drug effects and ultimately dose optimisation in order to anticipate important toxicities and prevent their occurrence by the administration of prophylactic treatments.

Rationale and use of epirubicin-based therapy in the adjuvant setting

The taxanes paclitaxel and docetaxel have an important role in the treatment of breast cancer, and numerous randomized trials have evaluated their efficacy for this indication. A systematic, evidence-based review was performed, which included all randomized, controlled trials evaluating taxanes for the treatment of early- or advanced-stage breast cancer that were identified in CANCERLIT and MEDLINE searches. The primary objectives of this review were to determine the dose and schedule for each taxane that was associated with the most favorable therapeutic index, and to determine whether (and under what circumstances) the taxanes improved survival. The search revealed 18 randomized phase II (n=1) or phase III (n=17) trials. For metastatic breast cancer, the dose and schedule associated with the most favorable therapeutic index for paclitaxel was 175 mg/m2 given as a 3-hour infusion every 3 weeks, and docetaxel was 60-100 mg/m2 given as a 1-hour infusion every 3 weeks. Survival was improved under the following circumstances: (1) when 4 cycles of paclitaxel (175 mg/m2 every 3 weeks) was given following 4 cycles of conventional doxorubicin- cyclophosphamide for axillary node-positive operable breast cancer, (2) when trastuzumab was added to paclitaxel as first-line therapy for metastatic breast cancer that overexpressed HER2/neu, and (3) when docetaxel was given as second-line therapy for anthracycline-resistant disease. Although a survival benefit was found for taxanes as a component of first-line therapy in two of six trials, the interpretation of both positive trials was confounded by a lack of crossover to taxane therapy in those who were initially randomized to receive standard therapy. The taxanes improve survival in patients with early-stage breast cancer and selected patients with metastatic breast cancer. Further research is necessary in order to identify the efficacy of docetaxel relative to paclitaxel, the optimal dose of docetaxel, the role of weekly taxane therapy, the role of trastuzumab plus taxanes in early-stage disease, and whether taxanes are more effective when given concomitantly or sequentially in patients with early-stage disease

Comparative effects of paclitaxel and docetaxel on the metabolism and pharmacokinetics of epirubicin in breast cancer patients

PURPOSE

To investigate whether paclitaxel and docetaxel influence the pharmacokinetics and metabolism of epirubicin.

PATIENTS AND METHODS

We studied the pharmacokinetics and biotransformation patterns of epirubicin in 27 cycles and 20 breast cancer patients. Four patients received epirubicin alone 90 mg/m(2) by intravenous (IV) bolus; eight patients received the same dose of epirubicin followed immediately by paclitaxel 175 mg/m(2) in a 3-hour infusion; the other eight patients received epirubicin 90 mg/m(2) followed immediately by docetaxel 70 mg/m(2) in a 1-hour infusion. Epirubicin and its metabolites, epirubicinol (EOL) and 7-deoxydoxorubicinone (7d-Aone), were identified by high-pressure liquid chromatography.

RESULTS

No pharmacokinetic interaction between the parent compound epirubicin and taxanes was detected. Conversely, a significant effect on epirubicin metabolism by both paclitaxel and docetaxel was found. Epirubicin given with paclitaxel or docetaxel yielded areas under the plasma concentration-time curves (AUC) for 7d-Aone 1. 7-fold and 1.9-fold higher (P <.05), respectively, than epirubicin alone. The appearance of two polar metabolites sensitive to glucuronidase was also significantly greater in both taxane groups. Quantitatively different metabolic rates and patterns for EOL were observed in the paclitaxel and docetaxel combinations. The EOL AUC after paclitaxel treatment (1,521 +/- 150 ng/mL*h) was significantly higher (P <.01) than the corresponding values after epirubicin administered either as a single agent (692 +/- 46 ng/mL*h) or in combination with docetaxel (848 +/- 237 ng/mL*h).

CONCLUSION

There is no apparent pharmacokinetic interaction between the parent compound epirubicin and paclitaxel or docetaxel. A different pattern of interaction between these taxanes and epirubicin metabolism is clearly evident.

Pharmacokinetics of anticancer agents in patients with impaired liver function

This report reviews published information on the clinical pharmacokinetics of antitumour agents in patients with liver dysfunction, associated with primary liver disease or liver metastases. Information was available for anthracyclines and their related compounds, antimetabolites, cyclophosphamide, vinca alkaloids, taxanes and epipodophyllotoxins. Changes in the pharmacokinetic profile or metabolism in patients with mild or severe hepatobiliary dysfunction are described and the relationships between serum levels, parameters employed for measuring hepatic function and toxic or therapeutic effects are examined. Current knowledge of the pharmacokinetics of antineoplastic agents in liver disease is far from complete, mostly obtained in small numbers of non-homogeneous patients often presenting only moderate liver dysfunction, and empirical guidelines for dose assessment are still largely applied in clinical practice. Because of the complex pathophysiological mechanisms of liver insufficiency in cancer patients, there is still doubt whether endogenous markers are useful. Although caution in treating cancer patients with liver insufficiency is compulsory, for most compounds there seems no need to recommend dose reductions for moderate impairment. However, for the tubulin acting agents, vincristine, vinblastine and possibly for paclitaxel and docetaxel, there is strong evidence that dose adjustment is mandatory in order to avoid excessive neutropenia and neurotoxicity.

On the importance of sensitivity to the dose-effect relationship in chemotherapy

The dose effect relationship of cytostatics is discussed from a theoretical point of view. Assuming tumour cell sensitivity as a continuum and an exponential distribution of cell probability density as a function of sensitivity the 'log kill' concept has been extended to a model describing the relation between dose and effect in malignant tumours. The model is based on only 3 parameters: The ratio between maximum and minimum sensitivity, the ratio between maximum and minimum cell probability density according to sensitivity and finally the product of dose and (minimum) sensitivity. The model demonstrates that the fractional tumour reduction intended is of major importance for the resulting curves. Dose effect curves describing a small fractional cell kill (0.5) are much steeper than curves describing a high one (to 10(-3)). Possible clinical implications of the model are discussed.

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.

The pharmacokinetics of high-dose epirubicin and of the cardioprotector ADR-529 given together with cyclophosphamide, 5-fluorouracil, and tamoxifen in metastatic breast-cancer patients

A high-pressure liquid chromatographic method for determination of the bisdioxopiperazine derivative ADR-529 (ICRF-187), a compound proven effective in protection against anthracycline-induced cardiotoxicity, has been developed. The limit of quantitation was 5 ng/ml using a narrow-bore 5-microns silica column and UV detection. The method was used for determination of pharmacokinetic profiles of ADR-529 after a 3-weekly i.v. administration of different doses of ADR-529 (600-1000 mg/m2) together with different doses of epirubicin (E, 60-100 mg/m2), fixed-dose cyclophosphamide (C, 600 mg/m2), fixed-dose 5-fluorouracil (F, 600 mg/m2), and daily administration of tamoxifen (T, 30 mg; CEF-T) in the treatment of patients with metastatic breast cancer. Pharmacokinetic parameters for epirubicin were also determined. The aim of the study was to determine (1) whether the pharmacokinetics of ADR-529 as part of a combination with CEF-T changes with increasing doses of ADR-529 and increasing doses of epirubicin and (2) whether the pharmacokinetics of epirubicin in the same combinations is altered with the administration of increasing doses of ADR-529. A total of 82 patients were included. A crossover study including 16 of the patients showed no significant difference in epirubicin pharmacokinetic parameters when epirubicin was given with or without concomitant administration of ADR-529. Apart from minor changes in the distributional half-lives, the pharmacokinetic parameters of epirubicin were not altered with increasing doses of ADR-529, nor were the pharmacokinetic parameters of ADR-529 itself. Escalating doses of epirubicin did not significantly alter the pharmacokinetic parameters of ADR-529 with the exception of a 30% increase in the terminal half-life and a decrease in total body clearance when the epirubicin dose was raised from 60 to 100 mg/m2. We conclude that concomitant administration of ADR-529 does not alter the distribution and elimination of epirubicin in doses suitable for preventing the anthracycline-induced cardiotoxicity.

Epirubicin. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in cancer chemotherapy

Epirubicin is the 4' epimer of the anthracycline antibiotic doxorubicin, and has been used alone or in combination with other cytotoxic agents in the treatment of a variety of malignancies. Comparative and noncomparative clinical trials have demonstrated that regimens containing conventional doses of epirubicin achieved equivalent objective response rates and overall median survival as similar doxorubicin-containing regimens in the treatment of advanced and early breast cancer, non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), non-Hodgkin's lymphoma, ovarian cancer, gastric cancer and nonresectable primary hepatocellular carcinoma. Recently, dose-intensive regimens of epirubicin have achieved high response rates in a number of malignancies including early and advanced breast cancer and lung cancer. The major acute dose-limiting toxicity of anthracyclines is myelosuppression. In vitro and clinical studies have shown that, at equimolar doses, epirubicin is less myelotoxic than doxorubicin. The lower haematological toxicity of epirubicin, as well as the recent introduction of supportive measures such as colony-stimulating factors, has allowed dose-intensification of epirubicin-containing regimens, which is particularly significant because of the definite dose-response relationship of anthracyclines. Cardiotoxicity, which is manifested clinically as irreversible congestive heart failure and/or cardiomyopathy, is the most important chronic cumulative dose-limiting toxicity of anthracyclines. Epirubicin has a lower propensity to produce cardiotoxic effects than doxorubicin, and its recommended maximum cumulative dose is almost double that of doxorubicin, thus allowing for more treatment cycles and/or higher doses of epirubicin. In summary, dose-intensive epirubicin-containing regimens, which are feasible due to its lower myelosuppression and cardiotoxicity, have produced high response rates in early breast cancer, a potentially curable malignancy, as well as advanced breast, and lung cancers. Furthermore, there is evidence to suggest that improved response rates can improve quality of life in some clinical settings, but whether this leads to prolonged survival has not yet been determined. Recently implemented supportive measures such as colony-stimulating factors, prophylactic antimicrobials and peripheral blood stem cell support may help achieve other potential advantages of dose-intensive epirubicin-containing regimens such as reductions in morbidity and length of hospital admissions.

A limited sampling method for estimation of the etoposide area under the curve

A limited sampling method for estimation of the etoposide area under the curve (AUC) is presented. The method was developed and validated in 23 patients (42 pharmacokinetic studies) with small-cell lung cancer (SCLC), limited disease. The patients received 100 mg/m2 etoposide as a 90-min intravenous infusion in combination with carboplatin, allowing for etoposide dose modification at a following course (25% increase or decrease) due to high or low nadir values for leukocytes or thrombocytes. Of the 42 pharmacokinetic studies, 27 were used in the model development and 15 were used in the model validation. Single regression analyses of the AUC versus the fitted concentrations for the model data set were performed at several time points. The analyses demonstrated high and essentially identical correlation coefficients in the interval between 2 and 21 h, with a maximal value of 0.96 being recorded at 4 h. Multiple regression analysis was then performed using fitted concentrations corresponding to 0.08-21 h. The best model for one sample was AUC = 1.01 x (dose level divided by 100 mg/m2) + 799 x C4 h, that for two samples was AUC = 1.43 x (dose level divided by 100 mg/m2) + 544 x C4 h + 1756 x C21 h, and that for three samples was AUC = 0.07 x (dose level divided by 100 mg/m2) + 110 x C5 min + 474 x C4 h + 1759 x C21 h. Not unexpectedly, the model validation revealed that the one-sample model was less precise than the two- or three-sample model [percentage of root mean squared error (RMSE%) = 11.6%, 7.1%, and 5.4%, respectively]. All models proved to be unbiased in the validation [percentage of mean predictive error (MPE%) +/- SE = 4.2% +/- 11.0%, 7.9% +/- 6.1%, and 6.3% +/- 5.3%, respectively]. The models were subsequently validated in 14 pharmacokinetic studies of patients with metastatic germ-cell tumours who were receiving combination chemotherapy with cisplatin and bleomycin plus 100 mg/m2 etoposide as a 90-min infusion. The RMSE% was 13.4%, 10.8%, and 9.0% and the MPE% +/- SE was -1.0% +/- 11.9%, 1.7% +/- 10.5%, and 2.7% +/- 7.9% for the one-, two-, and three-sample models, respectively. The limited sampling methods presented herein may prove to be a most valuable tool for therapeutic drug monitoring in regimens in which etoposide is given in combination with carboplatin or with cisplatin and bleomycin.

Epirubicin. Clinical pharmacology and dose-effect relationship

The pharmacokinetic properties of epirubicin are characterised by a triphasic plasma clearance, with half-lives for the initial (alpha), intermediate (beta) and terminal (gamma) elimination phases of approximately 3 minutes, 1 hour and 30 hours, respectively. These values are similar to or slightly shorter than the corresponding half-lives of doxorubicin. The total plasma clearance of epirubicin is approximately 50 L/h/m2, which is almost 2-fold higher than that of doxorubicin. This difference is mainly due to the relatively high volume of distribution of epirubicin, and the unique glucuronidation metabolic pathway of epirubicin and epirubicinol, which is not available to doxorubicin or doxorubicinol. Glucuronide metabolites of epirubicin and epirubicinol are not active per se, but could divert epirubicin from free radical formation, which may induce cardiotoxic effects. This may explain, at least in part, the lower cardiotoxicity of this new anthracycline relative to that of the parent compound. There is a linear relationship between the dose administered and area under the plasma concentration-time curve (AUC) values of both unchanged drug and metabolites, so that the total plasma clearance of epirubicin is constant with epirubicin doses ranging from 40 to 140 mg/m2. No variation in total plasma clearance as a function of age in the range of 31 to 74 years has been observed, and this parameter is unaffected by subsequent courses of treatment. Hepatic dysfunction causes an increase in the terminal elimination half-life of epirubicin, which is well correlated with serum bilirubin levels and which necessitates a reduction in epirubicin dosage. Epirubicin is responsible for a dose-dependent neutropenia, which is clearly related to drug exposure as established in pharmacodynamic studies. The maximum tolerated dose (MTD) of epirubicin was first established to be approximately 90 mg/m2 but this was re-examined recently and is now deemed to be approximately 150 mg/m2, which is about 2-fold higher than the MTD of doxorubicin. Cumulative cardiac toxicity occurs for both epirubicin and doxorubicin, but the dose ratio for equal risk is about 1.8 in favour of epirubicin (500 to 550 mg/m2 for doxorubicin vs 900 to 1000 mg/m2 for epirubicin). Consequently, there is not a higher risk of developing cardiotoxicity after administration of high dose epirubicin, since this adverse effect is associated with total cumulative anthracycline dose. In several controlled trials, epirubicin exhibited the same anticancer activity as doxorubicin when administered at equimolar doses to patients with advanced breast cancer.(ABSTRACT TRUNCATED AT 400 WORDS)

A limited sampling method for estimation of the carboplatin area under the curve

A limited sampling method for estimation of the carboplatin area under the curve (AUC) from one or two plasma concentration determination is presented. The model was conceived and developed using 43 pharmacokinetic studies in 15 patients with ovarian cancer (model data set) who received carboplatin in combination with cyclophosphamide. Linear regression analyses comparing the AUC and the drug concentration at a single time point (0.25-10 h after the end of the infusion) as calculated from the fitted exponential equations gave correlation coefficients as high as 0.97, with maximal correlations falling within the interval of 2-3.25 h. The model was validated prospectively in 9 patients with ovarian cancer (validation data set) who received the same treatment as did the model data set (21 pharmacokinetic studies), testing the equation AUC = 0.52 x C2.75 h + 0.92. Observed and estimated AUCs were correlated in the validation data set (r = 0.91). The mean predictive error (MPE% +/- SE) was -4.4% +/- 3.1% and the root mean squared error (RMSE%) was 13.9%. Multiple regression analysis revealed that adding a second sample drawn at 0.25 h (AUC = 0.053 x C0.25h + 0.401 x C2.75h + 0.628) improved the MPE% to -2.2% +/- 2.1% and the RMSE% to 9.4% (r = 0.96). We conclude that the carboplatin AUC can be estimated from a single plasma sample at 2.75 h or, more precisely, from two plasma samples at 0.25 and 2.75 h. The methods described may prove to be a handy tool for the calculation of approximate AUCs in trials of a size that would discourage detailed pharmacokinetic studies.

Pharmacokinetics and metabolism of epirubicin administered as i.v. bolus and 48-h infusion in patients with advanced soft-tissue sarcoma

We have studied the pharmacokinetics of epirubicin after its administration in sarcoma patients either as an i.v. bolus or as a 48-h infusion (5 courses each; 9 patients in total). Bolus injection was followed by a three exponential decay in plasma, with half-lives of 2.43 min, 1.95 h and 21.7 h; 48-h infusions were characterized by the very rapid establishment of a plasma plateau concentration followed by a biexponential decay after stopping the infusion. Pharmacokinetic parameters such as total plasma clearance, total volume of distribution, mean residence time and elimination half-life were similar, irrespective of the duration of the administration. In contrast, the relative amounts of the metabolites of epirubicin were reduced when the drug was administered over 48 h; in particular, the plasma levels of epirubicin glucuronide never exceeded those of epirubicin, which always occur after bolus injection. This may result from a lower availability of epirubicin for metabolism. These results now require validation in a larger group of patients using a cross-over design.

Epirubicin as a single agent therapy for the treatment of breast cancer--a pharmacokinetic and clinical study

Sixty women with breast cancer (mean age: 61 years; range 36-78 years) were treated with Epirubicin (4'epi-Doxorubicin), 60 mg m-2, as single drug therapy. The drug was administered as 2 hours' constant rate infusions. The pharmacokinetics of the drug during the first course of treatment was evaluated by measurements of the plasma concentration of Epirubicin at the end of the infusion period. There was a five-fold inter-individual variation of the dose-normalized maximum plasma concentration, which increased with increasing age of the patients. There was no correlation between this pharmacokinetic parameter and degree of obesity. An increase in maximum plasma concentration was associated with an increasing degree of alopecia (p = 0.025). Also the degree of nausea and vomiting showed a tendency to increase with increasing maximum plasma concentration (p = 0.07). Fifty four of the sixty patients entered in the present study were evaluable for clinical response. There was one CR (complete remission). Seventeen patients achieved PR (partial response), and twenty five patients had SD (stable disease). Eleven patients did not respond to treatment. The median maximum plasma concentrations were 322, 316, 336 and 288 ng ml-1 in patients with CR, PR, SD and PD, respectively. The results in the present study showed that 60 mg m-2 of Epirubicin given as a constant rate infusion over 2 hours is a useful alternative to more aggressive combination drug therapy for the treatment of breast cancer.

A randomized study of epirubicin at four different dose levels in advanced breast cancer. Feasibility of myelotoxicity prediction through single blood-sample measurement

Detailed pharmacokinetic analysis and subsequent evaluation of myelotoxicity were performed in 55 patients who had been randomized to 4 different doses of epirubicin (40, 60, 90 or 135 mg/m2 given i.v. every 3 weeks). A significantly positive correlation was demonstrated between the AUC and the myelotoxicity of epirubicin. A similar correlation was observed when the metabolite epirubicinol was also considered. The decrease in leucocyte count as expressed by the logarithmic ratio between nadir WBC and initial WBC was linearly correlated with the AUC of either epirubicin alone (r = -0.55, P less than 0.001) or epirubicin and epirubicinol together (r = -0.63, P less than 0.001). As a relationship between the concentration of epirubicin in a single plasma sample taken at 6 h following i.v. administration and the AUC of the drug has been established, a log-linear relationship between the expected decrease in leucocytes and the concentration at 6 h after administration could be calculated. The proposed model is expressed as the equation: log WBCnadir = log WBCinitial -0.0073 x c6 (ng/ml)-0.14.