Individual dose adaptation of anticancer drugs

A pharmacist check of patients' infection-related condition prior to drug preparation reduces anticancer drug wastage after mixing: a retrospective study

BACKGROUND

We previously reported that a standardized pharmacist check of medical orders related to the administration criteria of anticancer drugs prior to preparation of injectable anticancer drugs was useful for reducing drug wastage after mixing. To further reduce anticancer drug wastage after preparation, we added a pharmacist check of patients' infection-related condition to the previous protocol and assessed the effectiveness of the modified protocol for reducing injectable anticancer drug wastage.

METHODS

In addition to the administration criteria of anticancer drugs, patients' infection-related condition, which was based on a body temperature ≥ 37.5 °C or elevated C-reactive protein (CRP) or white blood cell (WBC) count from baseline, was added to pharmacists' checklist of items used previously to prepare injectable anticancer drugs. We retrospectively compared the number, type and cost of anticancer drugs discarded after preparation and the reasons for discarding these drugs between pre- and post-protocol modification.

RESULTS

The rate at which anticancer drugs were discarded after preparation was significantly reduced after introducing the modified protocol compared to the original protocol (0.288% [18/6253] vs. 0.095% [6/6331], P = 0.013). Furthermore, the number of cases for which mixed anticancer agents were discarded because of infection decreased from 11 (fever: n = 8; elevated CRP or WBC: n = 3) to one (elevated CRP: n = 1) a year.

CONCLUSIONS

In addition to the standard administration criteria of anticancer drugs, checking patients' infection-related condition, defined by a body temperature ≥ 37.5 °C or elevated CRP or WBC from baseline, before mixing by the pharmacist is useful for reducing anticancer drug wastage after preparation.

Electrochemical biosensors: a nexus for precision medicine

Precision medicine is a field with huge potential for improving a patient's quality of life, wherein therapeutic drug monitoring (TDM) can provide actionable insights. More importantly, incorrect drug dose is a common contributor to medical errors. However, current TDM practice is time-consuming and expensive, and requires specialised technicians. One solution is to use electrochemical biosensors (ECBs), which are inexpensive, portable, and highly sensitive. In this review, we explore the potential for ECBs as a technology for on-demand drug monitoring, including microneedles, continuous monitoring, synthetic biorecognition elements, and multi-material electrodes. We also highlight emerging strategies to achieve continuous drug monitoring, and conclude by appraising recent developments and providing an outlook for the field.

Optimal Control Theory for Personalized Therapeutic Regimens in Oncology: Background, History, Challenges, and Opportunities

Optimal control theory is branch of mathematics that aims to optimize a solution to a dynamical system. While the concept of using optimal control theory to improve treatment regimens in oncology is not novel, many of the early applications of this mathematical technique were not designed to work with routinely available data or produce results that can eventually be translated to the clinical setting. The purpose of this review is to discuss clinically relevant considerations for formulating and solving optimal control problems for treating cancer patients. Our review focuses on two of the most widely used cancer treatments, radiation therapy and systemic therapy, as they naturally lend themselves to optimal control theory as a means to personalize therapeutic plans in a rigorous fashion. To provide context for optimal control theory to address either of these two modalities, we first discuss the major limitations and difficulties oncologists face when considering alternate regimens for their patients. We then provide a brief introduction to optimal control theory before formulating the optimal control problem in the context of radiation and systemic therapy. We also summarize examples from the literature that illustrate these concepts. Finally, we present both challenges and opportunities for dramatically improving patient outcomes via the integration of clinically relevant, patient-specific, mathematical models and optimal control theory.

Verifying Antineoplastic Dosages Calculated According to Body Surface Area (BSA)

The increasing complexity of cancer chemotherapy makes it mandatory that pharmacists be familiar with these highly toxic agents. This column reviews various issues related to the preparation, dispensing, and administration of cancer chemotherapy, both commercially available and investigational.

Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling. We demonstrate how this modification can enable TDM applications by quantitatively and dynamically measuring the concentrations of several analytes—including an anticancer drug (doxorubicin), several TDM-requiring antidepressant and anti-seizure drugs, fructose and blood pH—in undiluted plasma. This hierarchical surface chemistry is widely applicable to many analytes and provides a generalized platform for SERS-based biosensing in complex real-world media.

Despite the high sensitivity of SERS analysis, non-specific binding of proteins can impact the effectiveness in biologically important media such as blood. Here the authors report a SERS substrate modified to prevent protein fouling and demonstrate drug detection in undiluted plasma.

Real-time, aptamer-based tracking of circulating therapeutic agents in living animals

A sensor capable of continuously measuring specific molecules in the bloodstream in vivo would give clinicians a valuable window into patients' health and their response to therapeutics. Such technology would enable truly personalized medicine, wherein therapeutic agents could be tailored with optimal doses for each patient to maximize efficacy and minimize side effects. Unfortunately, continuous, real-time measurement is currently only possible for a handful of targets, such as glucose, lactose, and oxygen, and the few existing platforms for continuous measurement are not generalizable for the monitoring of other analytes, such as small-molecule therapeutics. In response, we have developed a real-time biosensor capable of continuously tracking a wide range of circulating drugs in living subjects. Our microfluidic electrochemical detector for in vivo continuous monitoring (MEDIC) requires no exogenous reagents, operates at room temperature, and can be reconfigured to measure different target molecules by exchanging probes in a modular manner. To demonstrate the system's versatility, we measured therapeutic in vivo concentrations of doxorubicin (a chemotherapeutic) and kanamycin (an antibiotic) in live rats and in human whole blood for several hours with high sensitivity and specificity at subminute temporal resolution. We show that MEDIC can also obtain pharmacokinetic parameters for individual animals in real time. Accordingly, just as continuous glucose monitoring technology is currently revolutionizing diabetes care, we believe that MEDIC could be a powerful enabler for personalized medicine by ensuring delivery of optimal drug doses for individual patients based on direct detection of physiological parameters.

Toxicologic Pathology in the 21st Century

Toxicology is and will be heavily influenced by advances in many scientific disciplines. For toxicologic pathology, particularly relevant are the increasing array of molecular methods providing deeper insights into toxicity pathways, in vivo imaging techniques visualizing toxicodynamics and more powerful computers anticipated to allow (partly) automated morphological diagnoses. It appears unlikely that, in a foreseeable future, animal studies can be replaced by in silico and in vitro studies or longer term in vivo studies by investigations of biomarkers including toxicogenomics of shorter term studies, though the importance of such approaches will continue to increase. In addition to changes based on scientific progress, the work of toxicopathologists is and will be affected by social and financial factors, among them stagnating budgets, globalization, and outsourcing. The number of toxicopathologists in North America, Europe, and the Far East is not expected to grow. Many toxicopathologists will likely spend less time at the microscope but will be more heavily involved in early research activities, imaging, and as generalists with a broad biological understanding in evaluation and management of toxicity. Toxicologic pathology will remain important and is indispensable for validation of new methods, quality assurance of established methods, and for areas without good alternative methods.

Ideal vial size for bortezomib: real-world data on waste and cost reduction in treatment of multiple myeloma in Brazil

OBJECTIVES

Single-size vials of drugs may be a source of waste and increase in treatment costs. Bortezomib, indicated for multiple myeloma (MM) treatment, is available in 3.5-mg vials, a quantity higher than the average dose commonly prescribed. This analysis aimed to demonstrate, through real-world data, which would be the optimal vial presentation for bortezomib in Brazil and quantify the reduction in medication waste related to this option.

METHODS

From November 2007 to October 2009 all patients with MM treated with bortezomib were identified via the Evidências database. Analysis of prescribed, dispensed, and wasted doses, their costs and projections of the ideal vial size were performed.

RESULTS

Thirty-five patients (mean body surface area of 1.73 m(2)) received 509 infusions in 131 cycles of treatment (average of 3.77 cycles per patient). The average dose prescribed was 2.1 mg per infusion (95% confidence interval [CI] 1.97-2.26) with average waste of 39.5% of the vial content (95% CI 35.35-43.76). The mean waste per patient per day was 1.38 mg (95% CI 1.24-1.52). If a 3-mg vial were available, the average drug waste per patient per day would be 0.88 mg (95% CI 0.74-1.03) or 36.2% less. With a 2.5-mg vial the waste would be 1.05 mg (95% CI 0.81-1.29) or 23.9% less. If two presentations were available (2.5 mg and 0.5 mg), the waste would be 0.52 mg (95% CI 0.4-0.63) or 62.5% less. Considering the price of the different vials to be proportional to the original 3.5-mg vial, the cost would be also reduced by the same rates described above.

CONCLUSIONS

A simple adjustment in vial size may reduce the waste of bortezomib by 36% to 62% and can also reduce the cost of treatment.

Dose calculation of anticancer drugs

BACKGROUND

Anticancer drugs are characterized by a narrow therapeutic window and significant inter-patient variability in therapeutic and toxic effects. Current body surface area (BSA)-based dosing fails to standardize systemic anticancer drug exposure and other alternative dosing strategies also have their limitations. Just as important as the initial dose selection is the subsequent dose revision to ensure the dose is correct.

OBJECTIVE

To provide an insight into the different dose individualization and dose adjustment methods, their feasibility and applicability in daily oncology practice and to suggest a practical framework for dose calculation and a basis for future research.

METHODS

Review of relevant literature related to dose calculation of anticancer drugs.

RESULTS

Strategies using clinical parameters, genotype and phenotype markers, and therapeutic drug monitoring all have potential and each has a role for specific drugs. However, no one method is a practical dose calculation strategy for many or all drugs.

CONCLUSION

Given that BSA-dosing leads to significant underdosing it is not reasonable to use this as the sole method of dose calculation. Because of wide disparity in individual patient characteristics and elimination mechanisms, we are unlikely to find the 'Holy Grail' of a single individualized dosing strategy for every patient and anticancer drug in the near future. We propose a pragmatic, although invalidated system for initial dose calculation using dose clusters and structured subsequent dose revision based on treatment-related toxicities and therapeutic drug monitoring. These models need to be tested in clinical trials.

Chemotherapy Dosing Part I: Scientific Basis for Current Practice and Use of Body Surface Area

Cytotoxic chemotherapy is characterised by a low therapeutic index and significant variability in therapeutic and toxic effects. In an attempt to reduce this variability, most chemotherapy doses are individualised according to patient body surface area (BSA). This practice, which was introduced almost 50 years ago, clearly has practical and economic implications for the healthcare system. Furthermore, the clinical value of this approach has, in recent years, been questioned. Despite established practice, chemotherapy dose selection remains complicated, partly because treatment effects are difficult to measure, partly because drugs are used in combination with other treatment modalities, and also because the patient's condition may change with disease progression. Various patient-related factors can affect drug pharmacokinetics (PK) and pharmacodynamics (PD), for example organ function, expression and activity of metabolising enzymes, drug resistance, body size, gender, age, concomitant disease and co-administration of other drugs. These factors may be of clinical significance in chemotherapy dose determination and measures of PK, PD or both feature in attempts to devise more rigorous methods for chemotherapy dosing. Part I of this series of two reviews describes the history and clinical impact of BSA-based chemotherapy, and examines the scientific evidence to support BSA dosing. It evaluates the factors affecting PK and PD for specific drugs that could inform and refine dose determination.

Doxorubicin pharmacokinetics is correlated to the effect of induction therapy in children with acute myeloid leukemia

We studied the pharmacokinetics of doxorubicin in 41 children treated for newly diagnosed acute myeloid leukemia. Doxorubicin, 75 mg/m2 body surface area, was administered by constant i.v. infusion over 8 h. Four children with Down's syndrome (DS), 1.2-2.3 years old, had a median total body clearance of 523 ml/min/m2. The median clearance in non-DS children, 0.6-1.8 years old (n = 4) and 2.5-17.7 years old (n = 33), was 446 and 538 ml/min/m2, respectively. Patients who went into complete remission (CR) after induction therapy had a significantly higher median plasma concentration of doxorubicin than those who did not, 249 compared with 180 ng/ml, respectively (P = 0.036; analysis restricted to non-DS patients). Doxorubicin plasma concentration was an independent factor for CR, both in univariate (P = 0.031) and multivariate analysis including sex, age and white blood cell count at diagnosis (P = 0.021). Patients who reached CR had a significantly lower doxorubicin clearance than those who did not, 513 and 657 ml/min/m2, respectively (P = 0.017). In conclusion, doxorubicin plasma concentration and total body clearance during up-front treatment were correlated to the effect of induction therapy. Prospective studies should be performed to confirm the concentration-effect relationship and explore the possibility of therapeutic monitoring.

Implications of dose rounding of chemotherapy to the nearest vial size

GOALS OF WORK

There are practical implications of preparing cytotoxic doses calculated to the exact milligram. The objective here was to explore the magnitude of the effect of dose rounding to the nearest whole vial strength for some newly marketed expensive cytotoxic chemotherapy agents.

PATIENTS AND METHODS

Body surface areas (BSA) of 2838 adult patients presenting for chemotherapy at the Peter MacCallum Cancer Centre between May 1996 and December 2000 were calculated by using the DuBois and DuBois linear equation to two decimal places. Each individual dose of docetaxel, liposomal doxorubicin, gemcitabine, oxaliplatin and vinorelbine was calculated from the actual BSA based on the dose recommended in the approved drug product information. This calculated dose was then rounded upwards to the full next vial if the calculated dose exceeded above 50% of the next appropriate vial strength and was rounded downwards to the full previous vial if the calculated dose did not exceed above 50% of the next appropriate vial strength. Potential impacts on cost were calculated in Australian dollars for each drug for both the calculated and rounded dose on those instances where the difference was no greater than +/-5%.

MAIN RESULTS

The proportion of patients in whom the dose rounded to the nearest vial strength varied by not more than +/-5% was 89.5% for docetaxel, 60.4% for liposomal doxorubicin, 99.4% for gemcitabine, 34% for oxaliplatin and 56.3% for vinorelbine. The implications of dose rounding in financial terms are significant and project savings of 4-14.2%.

CONCLUSIONS

The judicious application of dose rounding of chemotherapy agents is possible without any negative clinical effect. It is feasible to dose round to the nearest vial for those cytotoxic agents that are available in multiple vial sizes.

Individualised Cancer Chemotherapy: Strategies and Performance of Prospective Studies on Therapeutic Drug Monitoring with Dose Adaptation

Therapeutic drug monitoring (TDM) is increasingly used in clinical practice for the optimisation of drug treatment. Although pharmacokinetic variability is an established factor involved in the variation of therapeutic outcome of many chemotherapeutic agents, the use of TDM in the field of oncology has been limited thus far. An important reason for this is that a therapeutic index for most anticancer agents has not been established; however, in the last 20 years, relationships between plasma drug concentrations and clinical outcome have been defined for various chemotherapeutic agents. Several attempts have been made to use these relationships for optimising the administration of chemotherapeutics by applying pharmacokinetically guided dosage. These prospective studies, individualising chemotherapy dose during therapy based on measured drug concentrations, are discussed in this review. We focus on the way a target value is defined, the methodologies used for dose adaptation and the way the performance of the dose-adaptation approach is evaluated. Furthermore, attention is paid to the results of the studies and the applicability of the strategies in clinical practice. It can be concluded that TDM may contribute to improving cancer chemotherapy in terms of patient outcome and survival and should therefore be further investigated.

[Treatment of cancer and hematological malignancy in elderly people: oncogeriatrics as a discipline for the future (Part I): geriatric evaluation and management of solid tumors]

PURPOSE

Fifty percent of cancer arise in people older than 65 year-old. Most clinical trials in cancer treatment are limited in patients younger than 65 year-old. We review literature describing particularity of cancer treatment in elderly patients.

CURRENT KNOWLEDGE AND KEY POINTS

Therapeutic decisions should be based on an estimation of the patient's life expectancy, and risks and benefits should be weighted up accordingly. Geriatric oncology is made of a geriatric evaluation of patient and of knowledge of clinical trial about elderly patients.

FUTURE PROSPECTS AND PROJECTS

We present in this issue the principle of geriatric evaluation and the results of recent clinical trial on elderly cancer patients.

A mulher e o cancro do pulmão**Textos referentes à mesa-redonda com o mesmo título organizada pela Comissão de Trabalho de «Pneumologia Oncológica». Coimbra, 13 de Abril de 2002

The epidemiology of lung cancer has changed in the last years in several countries all over the world. In the 19th century, the lung cancer was rare but it incidence increase drastically during the 20th century, and the tendency is to continue in the 20th century. Actually the lung cancer's incidence and mortality are higher in the developed countries, especially in Europe and Unites States of America, with a increasing in the women incidence. These geographic differences and gender differences are related with smoking habits. Women begin to smoke earlier and have more difficulty to stop, because of problems related with obesity; they have more sensibility to the carcinogens and the risk of lung cancer is 1.5 times higher than the men with the same habits. Adenocarcinoma is the more frequent histological type in young people, in the total of the women and in non-smokers. Many factors since tobacco, home and professional pollution, nutritional, associated diseases even genetic and hormonal factors have been investigated to define its influence in development in women lung cancer. It specificity in women with lung cancer is the common problem for the medical people to treat this disease (pathology).The literature about this problem is not clear, and is necessary to advance with many studies in this area with the objective to clarify this important question.

Particular aspects of platinum compounds used at present in cancer treatment

The history of platinum in cancer treatment began 150 years ago with the first synthesis of cisplatin; but it was not used in the clinic before 30 years ago. Then 3000 derivatives were synthesised and tested, with poor successes: three other derivatives only are available today. Clearly they are not more active, but they are less toxic than cisplatin, although two, carboplatin and nedaplatin, yield a cross-resistance, while one, oxaliplatin, does not. Their mechanisms of action are similar: these four pro-drugs form adducts with DNA, impairing DNA synthesis and repair then. Their pharmacokinetics are complicated since we always measure two overlapping pharmacokinetics: those of the parent compound and of the bound platinum. Cisplatin is now recommended for few cancers, it is replaced by less-toxic carboplatin, and therefore more easily used in combination. Oxaliplatin give interesting results in a number of cancers. The official recommendation in Japan for nedaplatin is head and neck, testicular, lung, oesophageal, ovarian, and cervical cancer.

Pharmacokinetics of doxorubicin in children with acute lymphoblastic leukemia: multi-institutional collaborative study

BACKGROUND

In adults, it has been shown that the pharmacokinetics of doxorubicin are highly variable, despite standardization of the dose based on body surface area (BSA). The purpose of this study was to determine the plasma concentrations of doxorubicin and its active metabolite doxorubicinol in children treated for acute lymphoblastic leukemia (ALL).

PROCEDURE

Children, 107 in number, aged 1.3-17.3 years, were studied at Day 1 of induction therapy according to the current Nordic protocol. Five infants, 3-9 months old, were also included. Plasma samples were drawn 23 hr after the start of a 24-hr infusion of doxorubicin 40 mg/m(2), and analyzed by reversed-phase liquid chromatography.

RESULTS

There was a more than 10-fold difference between patients in dose normalized plasma concentration of doxorubicin, median 62.8 ng/ml, range 22.6-334 ng/ml. The doxorubicin concentrations differed significantly between age groups (P = 0.003). Children aged 4-6 years had the highest doxorubicin concentrations, median 77.9 ng/ml, followed by 2-4-year-old children, median 64.3 ng/ml. Both younger and older children had median values of about 50 ng/ml. Patients with white blood cell (WBC) count > 50 x 10(9)/L at diagnosis had significantly lower doxorubicin concentrations, median 55.3 ng/ml, than those with WBC count < 10 x 10(9)/L, median 64.4 ng/ml (P = 0.015). There was no difference in doxorubicin concentration between boys and girls. No correlation was found between doxorubicin levels and serum aminotransferases or serum creatinine. The concentration of doxorubicinol was 13% (median value) of that of doxorubicin. Four infants, 7-9 months old, had plasma clearance between 350-431 ml/min/m(2), which is in the same range as in older children. A 3-month-old infant had a clearance of 181 ml/min/m(2).

CONCLUSIONS

The age groups who had the highest doxorubicin concentrations, (2-) 4-6-year-old children, are known to make up a large proportion of standard risk ALL cases with good prognosis. The correlation between doxorubicin plasma levels and clinical effect needs further study. The influence of age, body composition, and tumor burden on the pharmacokinetics of antineoplastic drugs should also be further explored, aiming at improvements in the current dosing regimen based on BSA.

Quantification of doxorubicin in plasma--a comparative study of capillary and venous blood sampling

Doxorubicin, an anthraquinone glycoside, is currently one of the clinically most important antineoplastic drugs. The aim of the present study was to identify potential concentration differences of doxorubicin in plasma from capillary and venous blood samples. Sixteen patients (seven females and nine males; median age: 37 years, range: 1-77 years) were included. The quantitative analysis of doxorubicin was carried out by reversed-phase liquid chromatography with fluorometric detection. The concentration of doxorubicin in capillary and venous samples were closely correlated (r=0.98; p<0.0001). The median plasma concentration ratio capillary/venous was 1.13 (95% confidence interval: 1.06-1.20) and not affected either by plasma drug concentration, age or the body mass index of the patient. The concentration ratio was significantly higher in males (median: 1.18) than in females (median: 1.01). The observed concentration differences of doxorubicin in plasma from capillary and venous samples are of minor importance only. Capillary blood sampling is recommended for use in pharmacokinetic studies of doxorubicin, especially in pediatric patients, in order to avoid sometimes traumatic venous blood sampling.

Effects of social housing condition on chemotherapeutic efficacy in a Shionogi carcinoma (SC115) mouse tumor model: influences of temporal factors, tumor size, and tumor growth rate

OBJECTIVE

The objective of this study was to investigate 1) whether social housing condition, tumor size, and tumor growth rate alter responses to chemotherapy and 2) whether the timing of tumor cell injection or chemotherapy initiation (relative to housing condition formation) influences tumor growth rate or the efficacy of chemotherapy.

METHODS

Mice were reared individually (I) or in groups (G). In experiment 1, mice were rehoused (IG or GI) or left in group housing (GG) immediately after tumor cell injection. In experiment 2, housing conditions (II, IG, GG, or GI) were formed when tumors weighed 1 g. Chemotherapy (adriamycin 4 mg/kg and cyclophosphamide 61.5 mg/kg IP) and exposure to acute novelty stress (15 min/d, 5 d/wk) were initiated 1 day after housing condition formation.

RESULTS

If chemotherapy was initiated when the tumor burden was undetectable (experiment 1), housing condition did not alter tumor response to chemotherapy, although IG mice lost the most weight and overall had the lowest probability of survival. If chemotherapy was initiated when tumors weighed 1 g (experiment 2), both tumor and host responses to chemotherapy were poorest for IG mice. Timing of tumor cell injection relative to housing condition formation also differentially influenced the rate of tumor growth in mice treated with the drug vehicle; in experiment 1, tumor growth rate was faster in GI and GG mice than in IG mice, whereas in experiment 2, the rate of tumor growth was faster in II mice than in GG and IG mice.

CONCLUSIONS

Altering the temporal relationships among social housing condition formation, tumor cell injection, and chemotherapy initiation differentially influences the rate of tumor growth and the efficacy of chemotherapy. Effects of housing condition are independent of tumor growth rate at chemotherapy initiation and, in terms of host responses, independent of tumor burden.

What is cancer chemotherapy?

The importance of chemotherapy for cure of cancer is increasing, especially with its use as adjuvants to local therapy. Furthermore, in advanced disease, when the tumour has disseminated from its place of origin, chemotherapy has an expanding role in efforts to relieve cancer-related symptoms and to prolong life. Despite its shortcomings, chemotherapy, therefore, is an important treatment modality in oncology and will probably remain so for considerable time. This presentation, within the frame of The Swedish Council on Technology Assessment in Health Care (SBU) project to review cancer chemotherapy, aims to provide a brief overview of the field cancer chemotherapy. It includes a historical perspective of cancer chemotherapy, some practical aspects and theoretical considerations with respect to the action of, resistance to and metabolism of these drugs. Furthermore, some outlooks into the nearest future with respect to ways to improve and develop cancer chemotherapy are provided as well as some aspects of chemotherapy from an employee-protection perspective.

Body surface area estimation in children using weight alone: application in paediatric oncology

The majority of chemotherapy regimens and trials specify doses of cytotoxic drugs normalized to body surface area. Estimation of BSA in paediatric patients is particularly problematic, as conventional nomograms require accurate determination of both height and weight. The chemotherapy standards group of the UKCCSG (United Kingdom Children's Cancer Study Group) has evaluated a method for calculation of body surface area (BSA) estimation, based solely on patient weight. In comparison with BSA estimations using 2 commonly used methods, which require both weight and height measurements, deviation in the estimate of BSA was less than 10%. This method may be extended to the dosing of chemotherapeutic agents in infants of body weight less than 10 kg, with appropriate recommendations for dose modification. Until better correlates of drug clearance, such as GFR for carboplatin, are identified BSA is used to standardize doses for most chemotherapeutic agents. The formula presented here provides a more robust and reliable method of calculation of BSA from weight alone. Although this approach has been shown to be equivalent to other currently used methods, care should be taken extending this calculation of BSA to children less than 10 kg, to obese patients and to those with cachexia.

Are medical oncologists biased in their treatment of the large woman with breast cancer?

PURPOSE

Obesity and breast cancer are common conditions that often coexist. Concerns of relative overdosing of chemotherapy in the large cancer patient have led clinicians to apply empiric dose reductions, 'cap' the body surface area (BSA) at 2 m2, or use ideal rather than actual body weight to calculate BSA. There are no data supporting or refuting these practices and their prevalence is unknown. We sought to determine the distribution of body size and prevalence of obesity in the breast cancer population of our cancer centre, and to determine clinician chemotherapy dosing practices in the era of modern adjuvant chemotherapy.

PATIENTS AND METHODS

Women with invasive breast cancer receiving systemic therapy at our institution between 1980 and 1998 were identified and their recorded height and weight were used to calculate BSA and body mass index (BMI). We reviewed the first cycle adjuvant chemotherapy dosing practices from 1990-1998. The ideal dose of chemotherapy was calculated based on calculated BSA, and then contrasted with the actual dose received at cycle one. Discrepancies were recorded and categorized, using the largest single drug reduction if more than one drug was reduced.

RESULTS

Mean BMI in the systemic therapy population was 26.4 +/- 5.3 kg/m2, 54% were overweight, 2% severely obese and 18% moderately so. Their mean BSA was 1.7 +/- 0.2 m2 and only 5% had a BSA > or = 2 m2. In the adjuvant chemotherapy subgroup, most patients received > or = 85% of their ideal dose. The mean dose reduction was 5.3 +/- 11.3% versus 9.9 +/- 11.3% in the BSA < 2 and > or = 2 m2 groups, respectively (p = 0.02), and 4.3 +/- 8.2% versus 6.7 +/- 13.1% in the BMI < 25 and > or = 25 kg/m2 groups, respectively (p = 0.008). While only 24% of chemotherapy dose reductions of > or = 15% were in the BSA > or = 2 m2 group, 76% were in the BMI > or = 25 kg/m2 group.

CONCLUSIONS

Obesity is prevalent in this breast cancer population. BSA is not a sensitive index of large body size. We consistently detected more frequent empiric dose reductions at cycle one of adjuvant chemotherapy, with reductions of greater magnitude in the largest women (BSA > or = 2 m2) and those who were overweight (BMI > or = 25 kg/m2).

Pharmacokinetically guided administration of chemotherapeutic agents

The current practice for the dose calculation of most anticancer agents is based on body surface area in m2, although lower interpatient variation in pharmacokinetic parameters has been reported with pharmacokinetically guided administration. As chemotherapeutic agents have a narrow therapeutic window, pharmacokinetically guided administration may lead to less toxicity and higher efficacy than administration on the basis of body surface area. Pharmacokinetically guided administration, using parameters such as area under the plasma concentration-time curve (AUC), steady-state plasma drug concentration and drug exposure time above a certain plasma concentration, has been studied for many antineoplastic agents. Assessment of pharmacokinetic profiles allows the characterisation of relationships between pharmacokinetic parameters and efficacy and toxicity. AUC appears to be more closely correlated with pharmacodynamics than does the dose per unit of body surface area. In particular, the AUC-guided administration of carboplatin has been extensively studied, based on the close relationship between the renal clearance of the drug and glomerular filtration rate. Several formulae and limited sampling models have been derived to predict the AUC of carboplatin. The relationship between AUC and pharmacodynamics has also been studied for other anticancer agents, for example fluorouracil, topotecan, etoposide, cisplatin and busulfan, but all less extensively than for carboplatin. The pharmacokinetically guided administration of these agents needs to be investigated further before the use of alternative administration formulae can become standard clinical practice. Prospective studies of pharmacokinetically guided versus surface area-based administration should be performed to validate pharmacokinetic-pharmacodynamic relationships and to facilitate optimal dosage of anticancer agents in the clinic.

Risk factors determining chemotherapeutic toxicity in patients with advanced colorectal cancer

Antitumour therapy in advanced colorectal cancer has limited efficacy. For decades, fluorouracil has been the main anticancer drug for the treatment of colorectal cancer. Recently, however, new agents have been introduced: raltitrexed, irinotecan and oxaliplatin. Currently, the dosage for an individual patient is calculated from the estimated body surface area of the patient. Toxicity, however, frequently necessitates decreasing the dosage, extending the dose interval or even discontinuing treatment. Risk factors with predictive value for toxicity have been identified in several studies. These risk factors are often determined by the pharmacokinetic and pharmacodynamic properties of the drug. In this review, the risk factors for toxicity of the cytotoxic agents used in the treatment of advanced colorectal cancer are considered. For fluorouracil, age, gender, performance status, genetic polymorphism of dihydropyridine dehydrogenase, drug administration schedule, circadian rhythm of plasma concentrations, history of previous chemotherapy-related diarrhoea, xerostomia, low neutrophil levels, and drug-drug interactions have been identified as affecting chemotherapeutic toxicity. For raltitrexed, gender and renal and hepatic impairment, and for oxaliplatin, renal impairment and circadian rhythm of plasma concentrations, respectively, can be considered as risk factors for toxicity. In addition, age, performance status, bilirubinaemia, genetic polymorphism of uridine 5'-diphosphate-glucuronyltransferase-1A1 and drug administration schedule have been shown to be related to irinotecan toxicity. The available literature suggests that dose adjustment based on these risk factors can be used to individualise the dose in order to decrease toxicity and to improve the therapeutic index. This also applies to therapeutic drug monitoring, which has been shown to be effective controlling the toxicity of fluorouracil in some studies. Future research is warranted to assess the potential advantage of dose individualisation of chemotherapy founded on risk factors, over direct dose calculation from the estimated body surface area, with regard to toxicity, therapeutic index, and quality of life, in patients with advanced colorectal cancer.

A comparative pharmacokinetic study of doxorubicin and 4'-epi-doxorubicin in children with acute lymphocytic leukemia using a limited sampling procedure

Antraquinone glycosides are an important class of antineoplastic drugs, frequently used for treatment of a variety of malignancies in children. Doxorubicin (Dox) is the most frequently used drug within this class of antineoplastics. 4'-epi-doxorubicin (Epi), a Dox isomer, was developed with the aim of reducing risks for fatal heart toxicity observed with Dox. The aim of the present study was to investigate the pharmacokinetics of Dox and Epi in children with acute lymphocytic leukemia. In total 31 patients (13 females and 18 males; median age 5.4 years; range 0.73-15.3 years) were studied using a simplified sampling procedure. The pharmacokinetic differences of the two drugs were established by their simultaneous administration. The plasma pharmacokinetics of neither Dox nor Epi correlated with the age of the patients. There were no gender differences in dose-normalized maximum concentrations of neither Dox nor of Epi. The inter-patient variation of the dose-normalized maximum concentrations of Dox and Epi is larger among females than among males. The Cmax ratio Dox/Epi was 1.39+/-0.19 (mean +/- SD). The pharmacokinetic differences of Dox and Epi in children, although less pronounced than in adults, are still of a magnitude that might be of clinical importance.

An improved HPLC method for therapeutic drug monitoring of daunorubicin, idarubicin, doxorubicin, epirubicin, and their 13-dihydro metabolites in human plasma

A single high-performance liquid chromatography (HPLC) method, suitable for the analysis of daunorubicin, idarubicin, doxorubicin, epirubicin, and their 13-dihydro metabolites is validated in the present study. Preparation of plasma samples was performed by a first extraction of analytes with a chloroform/1-heptanol mixture (9:1) and reextraction with ortophosphoric acid 0.1 M. The chromatographic analysis was carried out by reversed-phase isocratic elution of anthracyclines with a Supelcosil LC-CN 5 mm column (25 cm x 4.6 mm internal diameter; Supelco) and detection was accomplished by spectrofluorimetry at excitation and emission wavelengths of 480 and 560 nm, respectively. All anthracyclines eluted within 15 minutes of injection and the method appeared to be specific, because the chromatographic assay did not show interferences at the retention time of analytes. The linearity, evaluated over a concentration range of 0.4-10,000 ng/mL, gave regression coefficients better than 0.999, with recoveries of doxorubicin-doxorubicinol and epirubicin-epirubicinol of 67%-109% and 61%-109% respectively, and 93%-109% for the other compounds. The limits of detection and quantification were 0.4 ng/mL in a 50-mL sample (40 pg/injection) for all anthracyclines tested. The method proved to be precise and accurate, as the within-day and between-day coefficients of variation were less than 10% and the accuracy of the assay was in the range of 91%-107%. Overall results indicate that it is feasible to analyze all the anthracyclines used in clinical practice and their major metabolites with a single optimized method, thereby simplifying their monitoring in chemotherapeutic regimens of cancer patients.

Therapeutic drug monitoring opportunities in cancer therapy

Cancer is a common cause of death, and improvements in treatment are desperately needed. The high degree of variation in systemic exposure for a given dose and the relationships between blood concentrations and either toxic or antitumor effects would suggest that therapeutic drug monitoring is a potential mechanism for improving the treatment of individual patients. In this review, the case for therapeutic drug monitoring is made in a select number of commonly used cancer drugs and areas that require more concerted effort are highlighted.

Evaluation of a prediction model of cisplatin dose based on total platinum plasma concentration

The aim of this study was to validate prospectively a model of cisplatin dose adjustment. 27 patients (63 courses) with lung cancer were treated by a 5 day continuous infusion of cisplatin and etoposide. The dose of cisplatin was adjusted in order to reach a target plasma concentration of total platinum (TP) of 2000 mu/l at the end of the infusion. The target concentration was reached with a mean bias of 2.7% and a precision of 7.8%. The results were compared with those of a population of 38 patients (97 courses) with lung cancer and treated with the same protocol of chemotherapy, but without dose adjustment. The average dose adjustment was an increase of cisplatin dose of 20.2%. This augmentation was most important during the first course, decreasing during the following courses. There was also an increase in the etoposide AUC, although its dose was not modified. Toxicity to polymorphonuclear cells was significantly increased and was linked to etoposide AUC.

Quality of pharmacokinetic research in oncology

The usefulness of pharmacokinetically guided individualisation of drug therapy will depend, among other things, on the quality of the analytical and pharmacokinetic methods used. We surveyed the quality of analytical and pharmacokinetics methodology and reporting in a literature search of the oncology literature from 1987 to 1992, using the Medline database. Thirty articles that examined relationships between normal tissue toxicity and area under the plasma concentration-time curve (AUC) formed the study sample. Analytical procedures were adequately described in 77% of the articles, but details of validation of the assay were seriously deficient in the great majority of articles. Methods for calculation of AUC were also deficient in over half of the articles. The findings suggest that greater attention needs to be paid to the quality of pharmacokinetic investigation in oncology, otherwise progress in the use of pharmacokinetically guided individualisation of dosage may be hindered.