Role of body surface area in dosing of investigational anticancer agents in adults, 1991-2001

Fixed-dose capecitabine is feasible: results from a pharmacokinetic and pharmacogenetic study in metastatic breast cancer

The pro-drug capecitabine is approved for treatment of anthracycline- and paclitaxel-resistant metastatic breast cancer. However, toxicity and large interpatient pharmacokinetic variability occur despite body surface area (BSA)-dosing. We hypothesized that a fixed-dose schedule would simplify dosing and provide an effective and safe alternative to BSA-based dosing. We conducted an open label, single-arm, two-stage study of oral capecitabine with fixed starting dose (3,000 mg total daily dose in two divided doses × 14 days q21 days) in patients with metastatic breast cancer. We correlated pharmacodynamic endpoints [e.g., efficacy (response) per RECIST and toxicity], adherence and pharmacokinetics/pharmacogenetics. Sample size of 45 patients was required to detect a 25 % response rate from null response rate of 10 % using a Simon two-stage design. Twenty-six patients were enrolled in the first-stage and 21 were evaluable after a median of four cycles of capecitabine. Two thirds of patients received either the same dose or a dose 500 mg lower than what would have been administered with a commonly used 2,000 mg/m(2) BSA-dosing schedule. Eight patients had stable disease but progressed after a median of seven cycles. Despite a clinical benefit rate of 19 %, no RECIST responses were observed following the first stage and the study was closed. Dose-reductions were required for grade 2 hand-foot syndrome (28 %) and vomiting (5 %). Adherence was similar when using both patient-reported and Medication Event Monitoring System methods. High interpatient variability was observed for capecitabine and metabolite pharmacokinetics, but was not attributed to observed pharmacogenetic or BSA differences. Single agent activity of capecitabine was modest in our patients with estrogen receptor-positive or -negative metastatic breast cancer and comparable to recent studies. BSA was not the main source of pharmacokinetic variability. Fixed-dose capecitabine is feasible, and simplifies dosing.

The upregulation of dihydropyrimidine dehydrogenase in liver is involved in acquired resistance to 5-fluorouracil

BACKGROUND

Acquired resistance to 5-fluorouracil (5-FU) is one of the important reasons for failure in 5-FU-based chemotherapy. The upregulation of dihydropyrimidine dehydrogenase (DPD) in tumours was reported as an important factor for acquired 5-FU resistance. The aim of this study is to examine whether intra-hepatic DPD was involved in acquired 5-FU resistance.

METHODS

HT-29 human colorectal xenograft tumours were established in nude mice. After long-term exposure to 5-FU, some of the tumour became "resistant" and the others remained "sensitive" to 5-FU. DPD expression levels in the livers and tumours of "resistant", "sensitive" or untreated mice were examined, and pharmacokinetics of 5-FU in rats' plasma were investigated. Gimeracil, a DPD inhibitor, was checked whether it could reverse the reduced bioavailability of 5-FU.

RESULTS

DPD expression was upregulated obviously in tumours of "resistant" mice as reported previously. Importantly, DPD expression was also upregulated significantly in livers of "resistant" mice, compared with those of "sensitive" or untreated mice. Furthermore, the upregulation of DPD expression in livers led to accelerated metabolism of 5-FU. Gimeracil was found to reverse the reduced serum 5-FU concentration. The cultured tumour cells from 5-FU treated mice showed relative sensitivity to higher concentration of 5-FU, even the "resistant" tumour cells.

CONCLUSION

Our study suggested that the upregulation of DPD in liver may be involved in acquired resistance to 5-FU, and DPD inhibitors or increasing 5-FU dosage may have potential application in overcoming 5-FU acquired resistance.

Toxicity of weekly oral topotecan in relation to dosage for gynecologic malignancies: a phase I study

The aim of this study was to determine the dose of weekly oral topotecan that allows safe administration and to evaluate the pharmacokinetics of this dose in patients with recurrent gynecologic malignancies. The first cohort of patients received oral topotecan 6 mg/week administered orally on days 1, 8, and 15 of a 28-day regimen. A standard 3+3 dose-escalating phase design was used for dose levels II-V (8, 10, 12 and 14 mg/week). Toxicity was scored according to the Common Terminology Criteria for Adverse Events. Cumulative toxicity was summarized in the 6-12 mg/week combined cohort and 14 mg/week cohort separately. Pharmacokinetic samples were obtained for day 1, cycle 1 only in the expansion cohort (dose level V). Twenty-five patients received a total of 88 cycles of therapy. Hematologic toxicities of grade 3 (6-12 mg dose) were neutropenia (25%) and anemia (8.3%). Gastrointestinal toxicities of grade 3 were diarrhea (16.7%) and obstruction (8.3%, disease-related). Grade 3 or 4 (14 mg/week) hematologic toxicities consisted of neutropenia (38.5%), platelets (15.4%), anemia (15.4%), infection with neutropenia (7.7%), and thrombosis (7.7%). Gastrointestinal toxicities of grade 3 were diarrhea (7.7%), obstruction (7.7%), and vomiting (7.7%). One patient died secondary to neutropenic sepsis. One patient (4%; 95% confidence interval: 2.1, 22.3) showed a partial response and five patients (20%; 95% confidence interval: 7.6, 41.3) had stable disease. An oral topotecan dose of 14 mg/week for 3 consecutive weeks out of 4 is mostly associated with acceptable toxicities and may be considered for use in future single-agent phase II trials.

A guide to rational dosing of monoclonal antibodies

BACKGROUND AND OBJECTIVE

Dosing of therapeutic monoclonal antibodies (mAbs) is often based on body size, with the perception that body size-based dosing would reduce inter-subject variability in drug exposure. However, most mAbs are target specific with a relatively large therapeutic window and generally a small contribution of body size to pharmacokinetic variability. Therefore, the dosing paradigm for mAbs should be assessed in the context of these unique characteristics. The objective of this study was to review the current dosing strategy and to provide a scientific rationale for dosing of mAbs using a modelling and simulation approach.

METHODS

In this analysis, the body weight-based or body weight-independent (fixed) dosing regimens for mAbs were systematically evaluated. A generic two-compartment first-order elimination model was developed. Individual or population pharmacokinetic profiles were simulated as a function of the body weight effects on clearance (θ(BW_CL)) and on the central volume of distribution (θ(BW_V1)). The variability in exposure (the area under the serum concentration-time curve [AUC], trough serum concentration [C(min)] and peak serum concentration [C(max)]) was compared between body weight-based dosing and fixed dosing in the entire population. The deviation of exposure for light and heavy subjects from median body weight subjects was also measured. The simulation results were then evaluated with clinical pharmacokinetic characteristics of various mAbs that were given either by body weight-based dosing or by fixed dosing in the case study.

RESULTS

Results from this analysis demonstrated that exposure variability was dependent on the magnitude of the body weight effect on pharmacokinetics. In contrast to the conventional assumption, body weight-based dosing does not always offer advantages over fixed dosing in reducing exposure variability. In general, when the exponential functions of θ(BW_CL) and θ(BW_V1) in the population pharmacokinetic model are <0.5, fixed dosing results in less variability and less deviation than body weight-based dosing; when both θ(BW_CL) and θ(BW_V1) are >0.5, body weight-based dosing results in less variability and less deviation than fixed dosing. In the scenarios when either θ(BW_CL) or θ(BW_V1) is >0.5, the impact on exposure variability is different for each exposure measure. The case study demonstrated that most mAbs had little effect or a moderate body weight effect (θ(BW_CL) and θ(BW_V1) <0.5 or ∼0.5). The difference of variability in exposure between body weight-based and fixed dosing is generally less than 20% and the percentages of deviation for light and heavy subpopulations are less than 40%.

CONCLUSIONS

The analysis provided insights into the conditions under which either fixed or body weight-based dosing would be superior in reducing pharmacokinetic variability and exposure differences between light and heavy subjects across the population. The pharmacokinetic variability introduced by either dosing regimen is moderate relative to the variability generally observed in pharmacodynamics, efficacy and safety. Therefore, mAb dosing can be flexible. Given many practical advantages, fixed dosing is recommended to be the first option in first-in-human studies with mAbs. The dosing strategy in later stages of clinical development could then be determined based on combined knowledge of the body weight effect on pharmacokinetics, safety and efficacy from the early clinical trials.

Appropriate chemotherapy dosing for obese adult patients with cancer: American Society of Clinical Oncology clinical practice guideline

PURPOSE

To provide recommendations for appropriate cytotoxic chemotherapy dosing for obese adult patients with cancer.

METHODS

The American Society of Clinical Oncology convened a Panel of experts in medical and gynecologic oncology, clinical pharmacology, pharmacokinetics and pharmacogenetics, and biostatistics and a patient representative. MEDLINE searches identified studies published in English between 1996 and 2010, and a systematic review of the literature was conducted. A majority of studies involved breast, ovarian, colon, and lung cancers. This guideline does not address dosing for novel targeted agents.

RESULTS

Practice pattern studies demonstrate that up to 40% of obese patients receive limited chemotherapy doses that are not based on actual body weight. Concerns about toxicity or overdosing in obese patients with cancer, based on the use of actual body weight, are unfounded.

RECOMMENDATIONS

The Panel recommends that full weight-based cytotoxic chemotherapy doses be used to treat obese patients with cancer, particularly when the goal of treatment is cure. There is no evidence that short- or long-term toxicity is increased among obese patients receiving full weight-based doses. Most data indicate that myelosuppression is the same or less pronounced among the obese than the non-obese who are administered full weight-based doses. Clinicians should respond to all treatment-related toxicities in obese patients in the same ways they do for non-obese patients. The use of fixed-dose chemotherapy is rarely justified, but the Panel does recommend fixed dosing for a few select agents. The Panel recommends further research into the role of pharmacokinetics and pharmacogenetics to guide appropriate dosing of obese patients with cancer.

Technical note: Criterion validity of whole body surface area equations: a comparison using 3D laser scanning

Measurements of whole body surface area (WBSA) have important applications in numerous fields including biological anthropology, clinical medicine, biomechanics, and sports science. Currently, WBSA is most often estimated using predictive equations due to the complex and time consuming methods required for direct measurement. The main aim of this study was to identify whether there were significant and meaningful differences between WBSA measurements taken using a whole body three-dimensional (3D) scanner (criterion measure) and the estimates derived from each WBSA equation identified from a systematic review. The study also aimed to determine whether differences varied according to body mass index (BMI), sex, or athletic status. Fifteen WBSA equations were compared with direct measurements taken on 1,714 young adult subjects, aged 18-30 years, using the Vitus Smart 3D whole body scanner, including 1,452 subjects (753 males, 699 females) from the general Australian population and 262 rowers (148 males, 114 females). Mixed-design analysis of variances determined significant differences and accuracy was quantified using Bland-Altman analysis and effect sizes. Thirteen of the 15 equations overestimated WBSA. With a few exceptions, equations were accurate with a low-systematic error (bias ≤2%) and low-random error (standard deviation of the differences 1.5-3.0%). However, BMI did have a substantial impact with the accuracy of some WBSA equations varying between the four BMI categories. The Shuter and Aslani: Eur J Appl Physiol 82 (2000) 250-254 equation was identified as the most accurate equation and should be used for Western populations 18-30 years of age. Care must be taken when deciding which equation to use when estimating WBSA.

A Systems Biology Approach in Therapeutic Response Study for Different Dosing Regimens-a Modeling Study of Drug Effects on Tumor Growth using Hybrid Systems

Motivated by the frustration of translation of research advances in the molecular and cellular biology of cancer into treatment, this study calls for cross-disciplinary efforts and proposes a methodology of incorporating drug pharmacology information into drug therapeutic response modeling using a computational systems biology approach. The objectives are two fold. The first one is to involve effective mathematical modeling in the drug development stage to incorporate preclinical and clinical data in order to decrease costs of drug development and increase pipeline productivity, since it is extremely expensive and difficult to get the optimal compromise of dosage and schedule through empirical testing. The second objective is to provide valuable suggestions to adjust individual drug dosing regimens to improve therapeutic effects considering most anticancer agents have wide inter-individual pharmacokinetic variability and a narrow therapeutic index. A dynamic hybrid systems model is proposed to study drug antitumor effect from the perspective of tumor growth dynamics, specifically the dosing and schedule of the periodic drug intake, and a drug’s pharmacokinetics and pharmacodynamics information are linked together in the proposed model using a state-space approach. It is proved analytically that there exists an optimal drug dosage and interval administration point, and demonstrated through simulation study.

Evaluation of current practice: management of chemotherapy-related toxicities

Adverse effects induced by cytotoxic chemotherapy (CT) have been mostly evaluated in clinical trials. The aim of this study was to assess in a nonselected patients group the incidence of CT-related toxicities and to identify risk factors in daily practice. Patients treated with CT (except cisplatin-based or carboplatin-based CT), for a solid tumour, were included in a prospective multicentre observational study. Clinical parameters, renal function and albumin level were assessed at baseline. Multivariate logistic regression was used to identify risk factors of CT-related toxicities. A total of 502 patients were recruited in different types of oncology departments. During CT, 62% of patients experienced grade 2-4 toxicities. Haematological toxicities affected 34% of patients and 20% of patients developed an infection requiring antibiotics. For 55% of patients, toxicities induced dose reduction (59% of cases), CT delay (25%) or discontinuation (16%) according to the management habits in the investigating centre. Performance status≥1, breast cancer, lymphopenia, hypoalbuminaemia and clearance creatinine<60 ml/min were risk factors for haematological toxicity. Performance status≥1, hypoalbuminaemia, proteinuria and clearance creatinine<90 ml/min were risk factors for change of CT schedule. A majority of patients receiving CT experienced significant toxicity leading to change of standard CT protocol. Albumin, creatinine clearance and lymphocyte should be routinely monitored at baseline to manage CT and to prevent their toxicities.

Phase II trial of simple oral therapy with capecitabine and cyclophosphamide in patients with metastatic breast cancer: SWOG S0430

BACKGROUND

Interest in oral agents for the treatment of metastatic breast cancer (MBC) has increased because many patients prefer oral to i.v. regimens. We evaluated a simple oral combination of capecitabine with cyclophosphamide (CPA) for MBC.

METHODS

The trial was designed to determine whether or not combination therapy would achieve a 42% response rate (RR) using the Response Evaluation Criteria in Solid Tumors (RECIST) in MBC. Patients with two or fewer prior chemotherapy regimens for MBC were eligible. Those with estrogen receptor-positive MBC had to have progressed on endocrine therapy. Patients had measurable disease or elevated mucin (MUC)-1 antigen and received CPA, 100 mg daily on days 1-14, and capecitabine, 1,500 mg twice daily on days 8-21, in 21-day cycles.

RESULTS

In 96 eligible patients, the median progression-free survival (PFS) interval was 5.9 months (95% confidence interval [CI], 3.7-8.0 months) and median overall survival (OS) time was 18.8 months (95% CI, 13.1-22.0 months). The RR was 36% (95% CI, 26%-48%) in 80 patients with measurable disease. The MUC-1 antigen RR was 33% (95% CI, 20%-48%), occurring in 15 of 46 patients with elevated MUC-1 antigen. Toxicity was mild, with no treatment-related deaths.

CONCLUSIONS

PFS, OS, and RR outcomes with capecitabine plus CPA compare favorably with those of capecitabine monotherapy and combination therapy with bevacizumab, sorafenib, or ixabepilone. The addition of these other agents to capecitabine does not improve OS time in MBC patients, and this single-arm study does not suggest that the addition of CPA to capecitabine has this potential in an unselected MBC population. When OS prolongation is the goal, clinicians should choose single-agent capecitabine.

Individually tailored treatment with epirubicin and paclitaxel with or without capecitabine as first-line chemotherapy in metastatic breast cancer: a randomized multicenter trial

Anthracyclines and taxanes are active cytotoxic drugs in the treatment of early metastatic breast cancer. It is yet unclear whether addition of capecitabine to the combination of these drugs improves the treatment outcome. Patients with advanced breast cancer were randomized to first-line chemotherapy with a combination of epirubicin (Farmorubicin(®)) and paclitaxel (Taxol(®)) alone (ET) or in combination with capecitabine (Xeloda(®), TEX). Starting doses for ET were epirubicin 75 mg/m(2) plus paclitaxel 175 mg/m(2), and for TEX epirubicin 75 mg/m(2), paclitaxel 155 mg/m(2), and capecitabine 825 mg/m(2) BID for 14 days. Subsequently, doses were tailored related to side effects. Primary endpoint was progression-free survival (PFS); secondary endpoints were overall survival (OS), time to treatment failure (TTF), objective response (OR), safety and quality of life (QoL). 287 patients were randomized, 143 to ET and 144 to TEX. Median PFS was 10.8 months for patients treated with ET, and 12.4 months for those treated with TEX (HR 0.84, 95% CI 0.65-1.07, P = 0.16); median OS was 26.0 months for women in the ET versus 29.7 months in the TEX arm (HR 0.84, 95% CI 0.63-1.11, P = 0.22). OR was achieved in 44.8% (ET) and 54.2% (TEX), respectively (χ(2) 3.66, P = 0.16). TTF was significantly longer for patients treated with TEX, 6.0 months, versus 5.2 months following ET (HR 0.73, 95% CI 0.58-0.93, P = 0.009). Severe hematological side effects related to epirubicin and paclitaxel were evenly distributed between the treatment arms, mucositis, diarrhea, and Hand-Foot syndrome were significantly more frequent in the TEX arm. Toxicity-adjusted treatment with ET and TEX showed similar efficacy in terms of PFS, OS, and OR. In this trial with limited power, the addition of capecitabine to epirubicin and paclitaxel as first-line treatment did not translate into clinically relevant improvement of the outcome.

Prognostic value of chemotherapy-induced neutropenia in early-stage breast cancer

Neutropenia is one of the most important dose-limiting toxicities and often the reason for dose reduction. In this study we aimed to assess whether chemotherapy-induced neutropenia could be a marker of efficacy and associate with increased survival. Data from a retrospective survey for early breast cancer patients in our hospital were reviewed. Three hundred and thirty-five patients who had been treated with six cycles of cyclophosphamide, epirubicin, and fluorouracil (CEF) were studied. The association between chemotherapy-induced neutropenia and overall survival (OS) was assessed. According to a multivariate Cox model with time-varying covariates, hazard ratios of death were 0.434 (95% confidence interval (CI), 0.298-0.634; P < 0.001) for patients with mild neutropenia, and 0.640 (95% CI, 0.42-0.975; P = 0.038) for those with severe neutropenia. Neutropenia occurring in early breast cancer patients is an independent predictor of increased survival. These findings suggest that neutropenia in patients who receive chemotherapy is strongly associated with a better prognosis.

High dose methotrexate treatment in children with acute lymphoblastic leukaemia may be optimised by a weight-based dose calculation

BACKGROUND

The inter-individual variation in exposure to methotrexate is considerable after intravenous high dose methotrexate (HDMTX) administration and both under- and over exposures may have dire consequences. Thus, optimal dose individualisation is of paramount importance.

PROCEDURE

We studied how pharmacokinetic parameters were related to outcome in 340 patients with acute lymphoblastic leukaemia (ALL). A population pharmacokinetic model was developed with data from 1284 HDMTX courses in 304 children evaluating age, height, weight, body surface area (BSA), sex, serum creatinine and serum alanine aminotransferase as potential covariates.

RESULT

Body weight improved the population pharmacokinetic model significantly more than any of the other patient characteristics, indicating that body weight may be the better way of dose normalisation. In a logistic regression analysis, higher values of clearance as well as volume of distribution were related to increased relapse risk in the standard (SR) and intermediate risk (IR) groups as well as in the entire cohort. A higher weight was strongly associated with worse outcome in the SR and IR groups, (P = 0.0186 and 0.0121, respectively).

CONCLUSIONS

We conclude that dose normalisation of methotrexate according to body weigh may give more predictable pharmacokinetics of methotrexate and may also improve the outcome for children with ALL.

Chemotherapy dosing strategies in the obese, elderly, and thin patient: results of a nationwide survey

PURPOSE

Determining the optimal starting dose of chemotherapy (CHT) presents a considerable challenge when using body-surface area (BSA)-based dosing, particularly in obese, elderly, or thin patients. We sought to document the range of approaches employed when administering CHT to these patients.

METHODS

A questionnaire was developed by a panel of oncologists and mailed to all members of the Medical Oncology Group of Australia.

RESULTS

From 315 oncologists, 188 responded (response rate 59.7%). BSA-based dosing is standard practice for 176 (97.2%) of the responding oncologists. In the adjuvant disease setting, 23 (12.7%) use ideal rather than actual body weight (BW) to calculate BSA, or choose whichever is less. When treating obese patients, only 6.1% of respondents routinely use actual BW. Of the remainder, 69.5% either cap the dose at 2 m(2) or use ideal BW. In underweight patients, 95% (n = 171) routinely calculate BSA using actual BW. Forty one respondents (22.7%) routinely reduce dose in the fit elderly.

CONCLUSION

This analysis of BSA-based CHT dosing methods demonstrates significant variability in practice. Based on evidence from adjuvant studies showing that actual BSA-based dosing is desirable, a substantial number of Australian patients are being underdosed. Further education, together with ongoing research, is required to optimize individualized dosing for efficacy and tolerability.

Factors affecting the pharmacokinetics of pegylated liposomal doxorubicin in patients

PURPOSE

There is significant inter-patient variability in the pharmacokinetics of pegylated liposomal doxorubicin (PLD). Identification of factors affecting the pharmacokinetics of PLD would enable personalization of therapy. We previously reported that age, gender, body composition, and monocytes affect the clearance of other liposomal agents. Therefore, we evaluated how these factors affect the pharmacokinetics of PLD.

METHODS

Pharmacokinetic studies of PLD were performed as part of phase I and II studies in 70 patients with solid tumors or Kaposi's sarcoma. The effects of monocyte count, age, gender, and body composition on PLD clearance were examined.

RESULTS

There was a 15.3-fold variability in PLD clearance. Body surface area-based dosing did not significantly reduce the variability in PLD clearance. The mean ± SD clearance for patients <60 years old and ≥60 years old were 54.6 ± 28.5 and 23.3 ± 10.8 mL/h/m(2), respectively (P < 0.0001), and for female and male patients were 23.7 ± 18.8 and 55.6 ± 26.8 mL/h/m(2), respectively (P < 0.0001). A reduction in pre-cycle monocyte count was associated with a greater reduction in PLD clearance.

CONCLUSIONS

Age, gender, and monocyte counts appear to correlate with PLD clearance. Further investigation of the association between these factors, PLD pharmacokinetics, and clinical outcomes (efficacy and toxicity) is warranted. These effects on the pharmacokinetics of PLD may be an approach for personalizing PLD therapy and may affect other pegylated liposomes and nanoparticle agents.

Tailored chemotherapy doses based on toxicity in breast cancer result in similar quality of life values, irrespective of given dose levels

BACKGROUND

From March 1994 to March 1998, breast cancer patients (an estimated relapse risk with 70% or more within five years with standard therapy) were randomised to treatment with tailored fluorouracil, epirubicin, and cyclophosphamide (FEC) therapy or FEC followed by marrow-supported high dose therapy in the Scandinavian Breast Group 9401 study. The aim of the present paper was to investigate differences in toxicity and eight health-related quality of life (HRQoL) variables (physical functioning, role functioning, emotional functioning, social functioning, cognitive functioning, fatigue, nausea-vomiting, and global quality of life) between women in the six dose steps used in the tailored and granulocyte colony stimulating factor supported FEC-arm at the assessment point 16 weeks after random assignment to treatment.

METHODS

The European Organization and Treatment of Cancer Quality of Life Questionnaire EORTC QLQ-C30 were mailed to the patients.

RESULTS

A total of 157 (87%) in the tailored FEC-group responded to the questionnaire within the time frame 16 weeks after inclusion in the study. Overall, toxicity was low, reaching grade 1-2 also in the higher dose steps. There were no overall differences between the dose steps on any of the tested HRQoL variables. Patients at dose step 4 scored statistically significantly higher on physical functioning than patients at dose step 1 (p = 0.022) and compared to those at dose step 2 (p = 0.014). Patients at dose steps -2 and -1 (combined to one group) reported statistically significantly higher mean scores on cognitive functioning than patients at dose step 1 (p = 0.022).

CONCLUSION

Patients who received higher doses, based on the tailored dosing strategy, did not seem to have worse HRQoL than those who had lower doses.

Dose-tailoring of FEC adjuvant chemotherapy based on leukopenia is feasible and well tolerated. Toxicity and dose intensity in the Scandinavian Breast Group phase 3 adjuvant Trial SBG 2000-1

The SBG 2000-1 trial is a randomised study that investigates if dose-tailored adjuvant FEC therapy based on the individual's leukocyte nadir value can improve outcome. The study has included 1535 women with medium and high-risk breast cancer.

PATIENTS AND METHODS

After a first standard dosed FEC course (5-fluorouracil 600 mg/m(2), epirubicin 60 mg/mg(2) and cyclophosphamide 600 mg/m(2)), patients who did not reach leukopenia grade III or IV were randomised to standard doses (group standard) or doses tailored to achieve grade III leukopenia (group tailored) at courses 2-7. Patients who achieved leukopenia grade III or more after the first course were not randomised but continued on standard doses (group registered).

RESULTS

Both planned and actually delivered number of courses (seven) were the same in all three arms. The relative dose intensity was increased by a factor of 1.31 (E 1.22, C 1.43) for patients in the tailored arm compared to the expected on standard dose. Ninety percent of the patients in the tailored arm achieved leukopenia grade III-IV compared with 29% among patients randomised to standard dosed therapy. Dose tailoring was associated with acceptable acute non-haematological toxicity with more total alopecia, nausea, vomiting and fatigue.

CONCLUSION

Dose tailoring according to leukopenia was feasible. It led to an increased dose intensity and was associated with acceptable excess of acute non-haematological toxicity.

Therapeutic drug monitoring in cancer chemotherapy

For a select number of drugs, proper management of patients includes monitoring serum or plasma concentrations of the drugs and adjusting the doses accordingly - this practice is referred to as therapeutic drug monitoring (TDM). The need for TDM arises when pharmacokinetic variability of drugs is not easily accounted for by common clinical parameters. Many chemotherapeutic drugs have large interindividual variability, yet TDM is not commonplace in chemotherapy management. This review will discuss pharmacokinetics in the context of chemotherapeutic drugs, examine the few instances where TDM is currently used in the field of oncology and propose other drugs where TDM might be useful for dose adjustments in the management of chemotherapy.

Pharmacokinetic evaluation of doxorubicin plasma levels in normal and overweight patients with breast cancer and simulation of dose adjustment by different indexes of body mass

Although being used for decades in the treatment of several types of cancer, either alone or in association, only a few data about the pharmacokinetics of doxorubicin (DOX) in humans are available. DOX is frequently used in association with other anticancer drugs in the management of breast cancer. Pharmacokinetic data available in the literature show that after i.v. administration DOX follows a two-compartment open model, with a fast distribution phase followed by a very slow elimination phase. The objective of this work is to perform a pilot study in order to verify if the usual dose adjustment based on body surface area (BSA) would be producing the same plasma concentration-time profiles in patients with normal (<25) and above normal (>25) body mass index (BMI). In order to assess the pharmacokinetics of DOX after a short-term i.v. infusion of 60mg/m(2) of BSA, an experimental design using only five plasma samples of each patient was applied. Samples were collected at 0.00, 0.66 (right after the end of infusion), 1.66, 8.66, and 24.66h. DOX pharmacokinetic profiles were evaluated after quantification of DOX using a new HPLC method developed and validated. Pharmacokinetic parameters (AUC(0-24.66) and C(max)) were analyzed by non-compartmental and compartmental approaches. Significant differences (α=0.05) between overweight and normal weight groups were found with respect to AUC and C(max). After adjustment of dose by weight and by BMI, the compartmental model was used to simulate plasma concentrations and new values for C(max) and AUC(0-24.66) were calculated. The new values obtained using both body weight (BW) and BMI were closer to the normal group than those obtained with BSA. According to the simulation, the differences of AUC and C(max) between the overweight group and the group of patients with normal weight were lower when the dose was adjusted by BW and BMI. These results suggest that more studies must be conducted, with more patients, in order to evaluate the best dose adjustment for DOX in women with breast cancer and overweight.

Treatment of metastatic colorectal cancer in the elderly

OPINION STATEMENT

Metastatic colorectal cancer (CRC) is the second leading cause of cancer related mortality in the United States. The median age of patients at diagnosis is over 70, so as the American population ages, it can be expected that the incidence of CRC will also increase. There is limited prospective data regarding the safety and efficacy of chemotherapy in elderly patients with metastatic CRC. However, the data that are available suggest that elderly patients with a good performance status have a similar likelihood of response to currently available chemotherapy, though perhaps a somewhat higher likelihood of toxicities such as myelosuppression. This paper reviews the available data and recommendations for the treatment of this patient population.

Cost savings from dose rounding of biologic anticancer agents in adults

Purpose: The purpose of this project was to determine the cost savings related to a dose-rounding process for adult biologic anticancer agents.

Methods: Biologic anticancer agents prepared by the inpatient pharmacy were identified retrospectively through completed chemotherapy preparation checklists and medication orders on file in the pharmacy or by the clinical pharmacist for adult oncology from the medical records of patients in her practice. The specific products screened for evaluation were aldesleukin, bevacizumab, cetuximab, denileukin diftitox, gemtuzumab, rituximab, and trastuzumab. Data collected included drug name, ordered dose, rounded dose, and product vials not wasted. Specific drug costs were provided by the department’s purchasing office. The project was reviewed and approved by the institutional review board to allow retrospective data collection from patient records. Cost savings were evaluated retrospectively for the time period of January 1, 2005 through March 31, 2005.

Results: One hundred and twenty-six orders for biologic anticancer agents were processed by the pharmacy department during the 3-month time period of data collection. Dose rounding could reduce drug wastage for 42% of these orders. Potential cost savings from dose rounding was $24,434 for the 3-month interval evaluated. However, nonadherence to dose rounding for 29 rituximab orders decreased the actual cost savings to $15,922. Individual staff education was reinforced to address nonadherence.

Conclusion: Routine dose rounding of biologic anticancer agents to an amount within 10% of the ordered dose achieved cost savings through reduction of drug wastage at our institution.

Thymidylate synthase (TYMS) enhancer region genotype-directed phase II trial of oral capecitabine for 2nd line treatment of advanced pancreatic cancer

PURPOSE

The primary aim of this study was to characterize the 6-month overall survival and toxicity associated with second-line capecitabine treatment of advanced pancreatic cancer patients harboring the TYMS *2/*2 allele. The secondary aim was to analyze the response rate and pharmacokinetics of capecitabine-based therapy in this patient population. Lastly, TYMS, ATM and RecQ1 single nucleotide polymorphism were analyzed relative to overall survival in patients screened for study participation.

METHODS

Eighty patients with stage IV pancreatic cancer were screened for the *2/*2 TYMS allele. Patients with the *2/*2 TYMS polymorphism were treated with capecitabine, 1,000 mg/m2 twice daily for 14 consecutive days of a 21 day cycle. Screened patients not possessing TYMS *2/*2 were monitored for survival. Pharmacokinetic analysis was done during Cycle 1 of the therapy.

RESULTS

Sixteen of the 80 screened patients tested positive for *2/*2 TYMS variant. Four out of the 16 eligible patients were treated on study. The study was terminated early due to poor accrual and increased toxicity. Three patients experienced grade 3 non-hematologic toxicities of palmer-plantar erythrodysesthesia, diarrhea, nausea and vomiting. Grade 2 toxicities were similar and occurred in all patients. Only one patient was evaluable for response after completion of three cycles of therapy. The presence of the *2/*2 TYMS genotype in all of the screened patients trended toward a decreased overall survival.

CONCLUSION

To our knowledge, this study represents the first genotype-directed clinical trial for patients with pancreatic adenocarcinoma. Although the study was closed early, it appears capecitabine therapy in pancreatic cancer patients harboring the TYMS *2/*2 variant may be associated with increased non-hematologic toxicity. This study also demonstrates the challenges performing a genotype-directed study in the second-line setting for patients with advanced pancreatic cancer.

An exploratory study of body composition as a determinant of epirubicin pharmacokinetics and toxicity

PURPOSE

Although body composition has emerged as an important predictor of drug efficacy and toxicity, explanations for this association are unclear. Our goal was to investigate relationships between lean body mass (LBM), liver size/function and epirubicin pharmacokinetics (PK) and toxicity.

METHODS

Data from a clinical study (n = 24) of patients with breast cancer receiving adjuvant intravenous FE(100)C chemotherapy were used to examine relationships between LBM, liver size, and epirubicin clearance. Muscle tissue and liver mass were measured by analysis of computerized tomography cross-sectional images, and an extrapolation of muscle mass to total LBM compartment was employed. Population PK analysis of epirubicin was undertaken to test effects of body composition on epirubicin clearance and area under the curve (AUC).

RESULTS

Estimated LBM was extremely variable in this cohort ranging from 32.9 to 67.3 kg. LBM was associated with neutrophil nadir (r = 0.5, P = 0.023), and mean LBM was lower for patients presenting with toxicity compared to those where toxicity was absent (41.6 vs. 56.2 kg, P = 0.002); 33% of variance in clearance was explained by LBM and aspartate aminotransferase (AST). Liver mass was not related to epirubicin clearance likely due to larger livers presenting with larger fat content, but liver attenuation (degree of fat infiltration) and AST were associated with AUC.

CONCLUSION

To our knowledge, this is the first study to examine relationships between LBM, liver mass/function and epirubicin PK and toxicity. This exploratory work investigates the notion of organs and tissues having distinctive contributions to the distribution and metabolism of antineoplastic drugs.

The average body surface area of adult cancer patients in the UK: a multicentre retrospective study

The majority of chemotherapy drugs are dosed based on body surface area (BSA). No standard BSA values for patients being treated in the United Kingdom are available on which to base dose and cost calculations. We therefore retrospectively assessed the BSA of patients receiving chemotherapy treatment at three oncology centres in the UK between 1(st) January 2005 and 31(st) December 2005.A total of 3613 patients receiving chemotherapy for head and neck, ovarian, lung, upper GI/pancreas, breast or colorectal cancers were included. The overall mean BSA was 1.79 m(2) (95% CI 1.78-1.80) with a mean BSA for men of 1.91 m(2) (1.90-1.92) and 1.71 m(2) (1.70-1.72) for women. Results were consistent across the three centres. No significant differences were noted between treatment in the adjuvant or palliative setting in patients with breast or colorectal cancer. However, statistically significant, albeit small, differences were detected between some tumour groups.In view of the consistency of results between three geographically distinct UK cancer centres, we believe the results of this study may be generalised and used in future costings and budgeting for new chemotherapy agents in the UK.

Selective inhibition of MDR1 (ABCB1) by HM30181 increases oral bioavailability and therapeutic efficacy of paclitaxel

Multi-drug resistance 1 (MDR1, ABCB1), also known as P-glycoprotein (P-gp), restricts intestinal uptake of many drugs, and contributes to cellular resistance to cancer chemotherapy. In this study, we examined the pharmacologic characteristics of HM30181, a newly developed MDR1 inhibitor, and tested its capacity to increase the oral bioavailability and efficacy of paclitaxel, an anti-cancer drug usually given by intravenous injection. In the ATPase assay using MDR1-enriched vesicles, HM30181 showed the highest potency (IC(50)=0.63nM) among several MDR1 inhibitors, including cycloporin A, XR9576, and GF120918, and effectively blocked transepithelial transport of paclitaxel in MDCK monolayers (IC(50)=35.4nM). The ATPase inhibitory activity of HM30181 was highly selective to MDR1. HM30181 did not inhibit MRP1 (ABCC1), MRP2 (ABCC2), and MRP3 (ABCC3), and partially inhibited BCRP (ABCG2) only at very high concentrations. Importantly, co-administration of HM30181 (10mg/kg) greatly increased oral bioavailability of paclitaxel from 3.4% to 41.3% in rats. Moreover, oral co-administration of paclitaxel and HM30181 showed a tumor-inhibitory strength equal or superior to that of intravenous paclitaxel in the xenograft model in nude mice. These results identify HM30181 as a highly selective and potent inhibitor of MDR1, which in combination with paclitaxel, may provide an orally effective anti-tumor regimen.

Pharmacokinetically guided dose adjustment of 5-fluorouracil: a rational approach to improving therapeutic outcomes

Chemotherapy dosing of the fluoropyrimidine 5-fluorouracil (5-FU) is currently based on body surface area. However, body surface area-based dosing has been associated with clinically significant pharmacokinetic variability, and as such, dosing based on body surface area may be of limited use. The clinical activity of 5-FU is modest at standard doses, and in general, dosing is limited by the safety profile, with myelosuppression and gastrointestinal toxicity being the most commonly observed side effects. Various strategies have been developed to enhance the clinical activity of 5-FU, such as biochemical modulation, alterations in scheduling of administration, and the use of oral chemotherapy. Studies that have shown an association between plasma concentration with toxicity and clinical efficacy have shown that pharmacokinetically guided dose adjustments can substantially improve the therapeutic index of 5-FU treatment. These studies have shown that only 20%-30% of patients treated with a 5-FU-based regimen have 5-FU levels that are in the appropriate therapeutic range--approximately 40%-60% of patients are underdosed and 10%-20% of patients are overdosed. To date, 5-FU drug testing has not been widely used because of the lack of a simple, fast, and inexpensive method. Recent advances in testing based on liquid chromatography-mass spectroscopy and a nanoparticle antibody-based immunoassay for 5-FU may now allow for routine monitoring of 5-FU in clinical practice. We review the data on pharmacokinetically guided dose adjustment of 5-FU and discuss the potential of this approach to advance therapeutic outcomes.

Fixed dosing versus body size-based dosing of monoclonal antibodies in adult clinical trials

Although without clear scientific rationale, body size-based dosing is often used for administering monoclonal antibodies (mAbs). This simulation study compared the performance of body size-based and fixed dosing in reducing pharmacokinetic (PK) and/or pharmacodynamic (PD) variability in adults for 12 mAbs with published population PK and/or PD models. At the population level, 95th percentile intervals of concentration-time profiles, distribution, and variability of exposure for 1000 subjects after both dosing approaches were examined. At the individual level, the difference between the exposures of patients with extreme body sizes from the typical exposure following both approaches was compared. The results show that the 2 dosing approaches perform similarly across the mAbs investigated with fixed dosing being better for some mAbs and body size-based dosing being better for the others. Based on this finding, we recommend using fixed dosing in first-in-human (FIH) adult studies because it offers other advantages. When sufficient data become available, a full assessment of body size effect on PK/PD should be conducted to determine the optimal dosing approach for phase 3 trials. Other factors that may affect the selection of dosing approach were also discussed. Dosing approach for mAbs in the pediatric population is out of the scope of this study.

Delivered dose: a drug-centric phenotype for chemotherapy dose individualization

It is pointed out that genotype-based approaches are unlikely to be effective at dose individualization. Delivered dose, which refers to the amount of drug delivered to the point of action to be measured by quantitative imaging techniques, is a drug-centric phenotype that separates pharmacokinetic effects from pharmacodynamic effects. Delivered dose serves as a midway measurable numeric parameter between drug administration and therapy outcome. One potential way to reduce chemotherapy outcome variation is to individualize prescribed drug so that uniform delivered dose is achieved across the patient population.

Fixed dosing and pharmacokinetics of S-1 in Japanese cancer patients with large body surface areas

BACKGROUND

S-1 is an oral anticancer agent that combines tegafur (FT) with 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate. The recommended initial dose of S-1 is 120 mg/day for patients with a body surface area (BSA) of > or =1.5 m(2) in Japan.

METHODS

We examined the effects of using this fixed dose on the pharmacokinetics of FT, CDHP, and active 5-fluorouracil (5-FU) on the basis of actual BSA. The pharmacokinetics was compared between patients with a BSA of 1.5-1.75 m(2) and those with a BSA of > or =1.75 m(2).

RESULTS

The median areas under the time-concentration curves (AUCs) of 5-FU and CDHP were significantly lower in patients with a BSA of > or =1.75 m(2) than in those with a BSA of 1.5-1.75 m(2) (P = 0.005 and 0.006, respectively; Mann-Whitney U-test). There was no difference between the groups in the median AUC of FT.

CONCLUSION

Systemic exposure to 5-FU is significantly lower in Japanese cancer patients with a large BSA of >1.75 m(2) who received the recommended fixed dose of S-1.

Phase I study of ON 01910.Na, a novel modulator of the Polo-like kinase 1 pathway, in adult patients with solid tumors

PURPOSE

We conducted a first-in-man (to our knowledge) phase I study to determine the dose-limiting toxicities (DLTs), characterize the pharmacokinetic profile, and document any antitumor activity of ON 01910.Na, a new chemical entity that arrests cancer cells in G(2)/M by modulating mitotic regulatory pathways including polo-like kinase 1 (Plk1).

PATIENTS AND METHODS

Patients had solid tumors refractory to standard therapy. ON 01910.Na was administered as a 2-hour infusion on days 1, 4, 8, 11, 15, and 18 in 28-day cycles. The starting dose was 80 mg, and an accelerated titration schedule (single-patient cohorts) was used for escalation. Pharmacokinetics were studied on days 1 and 15 of cycle 1.

RESULTS

Twenty patients (11 women and nine men; age 46 to 73 years) were enrolled onto the study. Dose levels of 80, 160, 320, 480, 800, 1,280, 2,080, and 3,120 mg were evaluated in single-patient cohorts. A DLT and additional grade 2 toxicities made the 4,370-mg dose (n = 6) not tolerable, and the next lower dose cohort (3,120 mg) was expanded to six assessable patients. Toxicities were skeletal, abdominal, and tumor pain; nausea; urge to defecate; and fatigue. Hematologic toxicity was infrequent and mild. ON 01910.Na pharmacokinetics were characterized by a rapid distribution phase (distribution half-life, 1 hour) and a relatively slow elimination phase (elimination half-life, 27 hours). A refractory ovarian cancer patient had an objective response after four cycles and remained progression free for 24 months.

CONCLUSION

ON 01910.Na showed a distinct but moderate toxicity pattern. The recommended phase II dose of ON 01910.Na with this schedule of administration is 3,120 mg. Single-agent activity was documented in an ovarian cancer patient.

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.

Surface-enhanced Raman spectral measurements of 5-fluorouracil in saliva

The ability of surface-enhanced Raman spectroscopy (SERS) to measure 5-fluorouracil (5-FU) in saliva is presented. The approach is based on the capacity of Raman spectroscopy to provide a unique spectral signature for virtually every chemical, and the ability of SERS to provide microg/mL sensitivity. A simple sampling method, that employed 1-mm glass capillaries filled with silver-doped sol-gels, was developed to isolate 5-FU from potential interfering chemical components of saliva and simultaneously provide SERSactivity. The method involved treating a 1 mL saliva sample with 1 mL of acetic acid, drawing 10 microL of sample into a SERS-active capillary by syringe, and then measuring the SER spectrum. Quality SER spectra were obtained for samples containing as little as 2 microg of 5-FU in 1 mL saliva. The entire process, the acid pretreatment, extraction and spectral measurement, took less than 5 minutes. The SERS of 5-fluorouridine and 5-fluoro-2'-deoxyuridine, two major metabolites of 5-FU, were also measured and shown to have unique spectral peaks. These measurements suggest that disposable SERS-active capillaries could be used to measure 5-FU and metabolite concentrations in chemotherapy patient saliva, thereby providing metabolic data that would allow regulating dosage. Tentative vibrational mode assignments for 5-FU and its metabolites are also given.

Population pharmacokinetics of cyclophosphamide and metabolites in children with neuroblastoma: a report from the Children's Oncology Group

Cyclophosphamide-based regimens are front-line treatment for numerous pediatric malignancies; however, current dosing methods result in considerable interpatient variability in tumor response and toxicity. In this pediatric population, the authors' objectives were (1) to quantify and explain the pharmacokinetic variability of cyclophosphamide and 2 of its metabolites, hydroxycyclophosphamide (HCY) and carboxyethylphosphoramide mustard (CEPM), and (2) to apply a population pharmacokinetic model to describe the disposition of cyclophosphamide and these metabolites. A total of 196 blood samples were obtained from 22 children with neuroblastoma receiving intravenous cyclophosphamide (400 mg/m2/d) and topotecan. Blood samples were quantitated for concentrations of cyclophosphamide, HCY, and CEPM using liquid chromatography-mass spectrometry and analyzed using nonlinear mixed-effects modeling with the NONMEM software system. After model building was complete, the area under the concentration-time curve (AUC) was computed using NONMEM. Cyclophosphamide elimination was described by noninducible and inducible routes, with the latter producing HCY. Glomerular filtration rate was a covariate for the fractional elimination of HCY and its conversion to CEPM. Considerable interpatient variability was observed in the AUC of cyclophosphamide, HCY, and CEPM. These results represent a critical first step in developing pharmacokinetic-linked pharmacodynamic studies in children receiving cyclophosphamide to determine the clinical relevance of the pharmacokinetic variability in cyclophosphamide and its metabolites.

CYP2A6 and the plasma level of 5-chloro-2, 4-dihydroxypyridine are determinants of the pharmacokinetic variability of tegafur and 5-fluorouracil, respectively, in Japanese patients with cancer given S-1

S-1 is an oral anticancer agent composed of tegafur (FT), 5-chloro-2,4-dihydroxypyridine (CDHP), and potassium oxonate. CDHP is added to prevent degradation of 5-fluorouracil (5-FU) by inhibiting dihydropyrimidine dehydrogenase. CYP2A6 is involved in the biotransformation of FT to 5-FU. Thus, we prospectively analyzed the effects of the CYP2A6 genotype, plasma level of CDHP, and patient characteristics on the pharmacokinetic (PK) variability of FT and 5-FU. Fifty-four Japanese patients with metastatic or recurrent cancers who received S-1 were enrolled. The CYP2A6 polymorphisms (*4A, *7, and *9) with deficient or reduced activity were analyzed. All subjects were classified into three groups according to their CYP2A6 genotype: wild type (*1/*1), one-variant allele (*1/any), or two-variant alleles (combination other than *1). The PK of FT, 5-FU, and CDHP were measured on day 1 of treatment. Multivariate regression analysis revealed that oral clearance of FT was associated with the CYP2A6 genotype (analysis of variance [ANOVA], P = 0.000838). The oral clearance of FT seen in patients with the two-variant alleles was significantly lower than those in wild type and the one-variant allele (95% confidence intervals 0.75-2.41 and 0.41-1.82, respectively; Tukey-Kramer test). The area under the time-concentration curve (AUC) of 5-FU was significantly correlated with the AUC of CDHP (ANOVA, P = 0.00126). The AUC of 5-FU and CDHP were inversely correlated with creatinine clearance (ANOVA, P = 0.0164 and P = 0.000762, respectively). Although the CYP2A6 variants are the cause of the PK variability of FT, the AUC of CDHP affected by renal function is the key determinant of the variability in the PK of 5-FU.

Phase I Study of a Novel Capecitabine Schedule Based on the Norton-Simon Mathematical Model in Patients With Metastatic Breast Cancer

Purpose

This study was conducted to determine, in patients with advanced-stage breast cancer, the maximum tolerated dose (MTD) of capecitabine administered orally for 7 days followed by a 7-day rest (7/7), a schedule based on a mathematical method for the optimization of anticancer drug scheduling.

Patients and Methods

Eligible patients had measurable, metastatic breast cancer. There was no limit to number of prior treatments. A standard, three-patients-per-cohort dose-escalation scheme used flat-dose capecitabine beginning at 1,500 mg orally twice daily (bid) on a 7/7 schedule. Each cohort was monitored for 28 days before escalation to the next cohort to assess for delayed toxicity. Response was evaluated radiographically every 12 weeks; toxicity was assessed every 2 weeks.

Results

Twenty-one patients were treated on study. The most frequently reported treatment-related grade 2/3 adverse events were hand-foot syndrome (29%), leukopenia/neutropenia (24%), and fatigue (19%). Grade 3 toxicity was transient and easily managed. Three patients experienced grade 3 hand-foot syndrome; one of these patients had grade 3 diarrhea. There were no grade 4 events. The MTD of capecitabine 7/7 is 2,000 mg twice daily.

Conclusion

As predicted by mathematical modeling, capecitabine dosing for 7 days followed by a 7-day rest is well tolerated. Efficacy of this schedule is being determined in a phase II clinical trial in patients with advanced breast cancer.