Significant Effect of Capecitabine on the Pharmacokinetics and Pharmacodynamics of Warfarin in Patients With Cancer

In vivo evaluation of pharmacokinetic drug-drug interactions between fluorinated pyrimidine anticancer drugs, 5-fluorouracil and capecitabin, and an anticoagulant, warfarin

Warfarin is a common anticoagulant and has demonstrated interactions with several drugs. Among them, as a serious adverse event, a case of death due to the enhanced warfarin action owing to its combined use with a fluoropyrimidine anticancer drug has been reported, but the detailed mechanism has not been elucidated.Some reports have advocated that fluorinated pyrimidine anticancer drugs reduce cytochrome P450 2C9 expression, leading to the enhanced pharmacological effects of warfarin.The purpose of this study was to clarify the mechanisms of drug-drug interactions between warfarin and 5-fluorouracil (5-FU) and capecitabine in vivo using rats. Rats were administered warfarin in combination with 5-FU (15 mg/kg/d) or capecitabine (15 mg/kg/d) for 7 d. Prothrombin time (PT) and activated partial thromboplastin time were significantly prolonged in the warfarin plus 5-FU or capecitabine groups compared with those in the warfarin alone group. No significant difference was observed in the area under the plasma concentration-time curve of the warfarin alone group compared with the warfarin with 5-FU or capecitabine groups.These data suggest that the enhancement of warfarin efficacy caused by the combination of 5-FU or capecitabine was due to a pharmacological interaction rather than a pharmacokinetic interaction.

Capecitabine and Warfarin Interaction: A Case Report With Review of Literature and Management Options

Capecitabine is an orally active prodrug of 5-fluorouracil with improved safety and efficacy that is extensively used as an antineoplastic agent. It is converted to 5-Fluorouracil in the liver and tumor tissues. In vitro assays did not reveal any significant potential for interaction between capecitabine and its metabolites with warfarin. However, several reports provided clinical evidence of such interaction resulting in an elevated international normalized ratio (INR) and bleeding. Here, we report another case of capecitabine and warfarin concurrent administration that resulted in sub- or supra- therapeutic INR without any bleeding episode or venous-thromboembolic event through the follow-up period. Moreover, a review of available management options is also presented in this paper.

Effect of 5-fluorouracil on mRNA expression of drug metabolizing enzyme and transporter genes in human hepatoma cell lines

Fluoropyrimidines such as 5-fluorouracil (5-FU) are well known to have drug-drug interactions with anticoagulant medications such as warfarin. This study investigated the mRNA expression of pharmacokinetic (PK)-related genes in response to 5-FU using the hepatocarcinoma cell lines after examining relevant gene expression via RNA sequencing. We used HepaRG cells for 5-FU treatment analysis because these cells displayed PK-related gene expression. 5-FU exposure significantly reduced cytochrome P450 3A4 (CYP3A4) mRNA expression. Additionally, the mRNA expression of nuclear receptor subfamily 1 group I member 2 (also known as pregnane X receptor), a nuclear receptor transcription factor that promotes the expression of many CYP genes, was also decreased in HepaRG cells following 5-FU treatment. The mRNA expressions of the CYP2B6 and ATP-binding cassette transporter genes were decreased after 5-FU treatment. This study revealed that 5-FU treatment reduced PK-related gene expression in HepaRG cells. These findings should be useful for further drug-drug interaction research.

Prediction of the impact of CYP2C9 and VKORC1 genotypes on warfarin-sorafenib interactions in whites and Asians

Aim: To predict the impact of the different CYP2C9 and VKORC1 genotypes on warfarin-sorafenib interactions in whites and Asians. Materials & methods: The influences of the CYP2C9*1/*3 and VKORC1 -1639 A/A genotypes on increases in anticoagulation responses (international normalized ratio [INR]) in the presence of sorafenib were predicted using the population pharmacokinetic/pharmacodynamic (PK/PD) model in whites and Asians. Results: INRs were predicted to be 2.0-2.1- versus 1.8-1.9-times higher in the presence of sorafenib in the CYP2C9 (*1/*1 vs *1/*3) groups than those for warfarin alone in both whites and Asians. INRs were also predicted to be 2.1-2.2- versus 1.9-2.1-times higher in the VKORC1 (GG or GA vs AA) groups. Conclusion: Warfarin-sorafenib interactions might be similar irrespective of CYP2C9 and VKORC1 genotypes or ethnicity.

Onco-cardiology: Drug-drug interactions of antineoplastic and cardiovascular drugs

Cardiovascular diseases (CVD) and cancer are still the leading causes of death. There are many common etiologic factors, especially smoking and obesity. Therefore, it is not uncommon for CVD and cancer to coexist. Drug-drug interactions (DDIs) inevitably occur in this group of patients, where polypharmacy is increasing due to older age and multiple comorbidities. However, multidisciplinary studies, especially close collaboration of medical oncologists and cardiologists, who deals with the diagnosis and treatment of these diseases, awareness and preventive approaches to DDIs may reduce serious morbidity and mortality. In this review, information about the common treatments used in cardiology and oncology and possible DDIs are discussed.

Oral Anticoagulants in Japanese Patients with Atrial Fibrillation and Active Cancer

Objective Oral anticoagulants (OACs), which include direct oral anticoagulants (DOACs) and warfarin, are widely used for the prevention of thromboembolic events in patients with atrial fibrillation (AF). Cancer is associated with a prothrombotic state as well as an increased bleeding risk. Few data are available on the efficacy and safety of OACs in Japanese cancer patients with AF. We sought to investigate the efficacy and safety of OACs in this population. Methods This retrospective cohort study included active cancer patients in whom AF was recorded by electrocardiography in our hospital from January 2014 to December 2016 and who were treated with DOACs or warfarin. Patients were followed for 1 year. The study outcomes were stroke or systemic embolism and major bleeding. Result A total of 224 patients with AF and active cancer were treated with OACs (DOACs, n=127; warfarin, n=97). Overall, stroke or systemic embolism and major bleeding occurred in seven (3.8%/year) and eight (4.9%/year) patients, respectively. Stroke or systemic embolism occurred in three patients in the DOAC group (2.8%/year) and four patients in the warfarin group (5.4%/year). Major bleeding occurred in four patients in the DOAC group (4.0%/year) and four patients in the warfarin group (6.5%/year). Conclusion The rates of stroke or systemic embolism and major bleeding events were not negligible among Japanese cancer patients with AF receiving OACs. Further investigations on the optimal management of Japanese patients with AF and cancer are needed.

Anticoagulation in Cancer Patients: a Summary of Pitfalls to Avoid

PURPOSE OF REVIEW

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality in cancer patients, and its management is often associated with complications including risk of recurrent VTE and bleeding. Here, we review the current data on pitfalls during anticoagulation in cancer patients and measures necessary to avoid them.

RECENT FINDINGS

Although low-molecular-weight heparin monotherapy has been the standard of treatment for several years, emerging data for direct oral anticoagulants (DOACs) are leading to new paradigms in treatment. Reports of recent randomized trials suggest a lower risk of recurrent thrombosis but higher risk of bleeding, particularly in gastrointestinal cancer patients, with DOACs. Careful patient selection and individualization of therapy based on risk of bleeding as well as recurrent VTE are keys. Problems like bleeding, recurrence, thrombocytopenia, drug-drug interactions, renal impairment, nausea-vomiting along with concerns about adherence arise during anticoagulation in cancer patients. However, with adequate pre-treatment assessment, correct anticoagulant selection and proper monitoring during anticoagulation, these issues can be addressed safely and effectively.

Incidence, risk factors, and outcomes of venous thromboembolism after oncologic surgery: A systematic review and meta-analysis

BACKGROUND

The risk and prognosis of VTE associated with oncologic surgery need to be quantified to guide patient management. We aimed to examine the availability of data and to report the incidence of venous thromboembolism (VTE) in cancer patients after surgery, as well as the clinical outcomes of VTE following oncologic surgery.

METHODS

We searched multiple databases for terms related to VTE after oncologic surgery from inception to November 1, 2017. A random-effects meta-analysis was done to calculate the pooled incidence of VTE.

RESULTS

Of the 8611 citations identified, 136 studies including 1,481,659 patients met the eligibility criteria. The overall incidence of VTE was estimated to be 2.3% (95% CI 2.1-2.5). Bone and soft tissue cancer (10.6%, 95% CI 2.9-18.2) and lung cancer (8.1%, 95% CI 3.7-12.6) were associated with the highest and second highest risk of postoperative VTE, respectively. Age (standardized mean difference [SMD] = 0.46, 95% CI 0.40-0.53; I² = 93.8%), radiation (OR 1.29, 95% CI 1.03-1.62; I² = 34.6%), transfusion (OR 1.96, 95% CI 1.48-2.59; I² = 57.0%), and operative time (SMD = 1.12, 95% CI 1.07-1.16; I² = 100%) were possible risk factors for postoperative VTE. Patients with VTE versus those without had increased odds of all-cause fatal events (11.15, 95% CI 4.07-30.56; I² = 92.0%).

CONCLUSIONS

The risk of VTE after oncologic surgery remains high, and this risk varied according to the cancer type, study region, surgical location, and thromboprophylactic strategy. VTE is associated with increased mortality at the early stage of cancer surgery.

Conceptualizing multiple drug use in patients with comorbidity and multimorbidity: proposal for standard definitions beyond the term polypharmacy

With older and aging populations, patients experience multiple chronic diseases at the same time. Individual chronic disease guidelines often recommend pharmacological therapies as a key intervention, resulting in patients being prescribed multiple regular medications for their different diseases. Although the term "polypharmacy" has been applied to the use of multiple medications, there is no consistent definition, and this term is now being used all inclusively. To improve both scientific rigor and optimal patient care, it is crucial that a standard terminology is used, which reclassifies the term "polypharmacy" into distinct phenotypes relating to the index chronic disease, additional conditions to the index (comorbidity), or the experience of multiple chronic conditions at the same time (multimorbidity). Using three exemplar index conditions; heart failure, type 2 diabetes, and breast cancer, we propose the reclassification of the term "polypharmacy" into three distinct phenotypes. First, index drug or multi-index drug therapy, where each index condition creates multiple drug use for that condition; second, codrug therapy, where addition of other comorbid conditions increases the multiple drug use and may influence the management of the index disease and third, multidrug therapy, where adult population with multimorbidity may be on many drugs. This article reviews guidelines for the individual exemplars to develop the basis for the new terms and then develops the pharmacoepidemiology of multiple drug use further by reviewing the evidence on the relationship between the phenotypic classification and important outcomes. The importance of standardizing "polypharmacy" terminology for the scientific agenda and clinical practice is that it relates to an index condition or disease safety outcomes including drug interactions, adverse side effects in hospital admissions, and related "polypill" concept.

Pharmacokinetics of Chemotherapy in the Older Patient

Background

The number of individuals aged 65 years and older is growing rapidly, and the majority of cancers are diagnosed in this age group. Age-related changes in physiology can affect chemotherapy pharmacokinetics and pharmacodynamics in older patients.

Methods

We review the literature regarding the impact of age on the pharmacokinetics of commonly used chemotherapy drugs and discuss age-related changes in physiology and pharmacology that can affect chemotherapy tolerance in older patients.

Results

The data on age-related changes in chemotherapy pharmacokinetics are conflicting. While a few studies report age-related differences in chemotherapy pharmacokinetics, most found no significant difference or subtle differences in pharmacokinetics with aging. A difference in pharmacodynamics was commonly seen, however, with older patients at increased risk of myelosuppression and toxicity from age-related decline in organ function. The majority of these studies were performed in a small cohort of patients, thus limiting the generalizability of these results.

Conclusions

Additional studies are needed to address the pharmacokinetics and pharmacodynamics of cancer therapies in the older patient. Multicenter pharmacokinetic studies of adequate sample size, which include a thorough evaluation of physiologic factors and geriatric assessment parameters, would provide further insight into the factors affecting treatment tolerance. These studies would also help to guide appropriate chemotherapy dosing and interventions in order to maximize efficacy and minimize toxicity in the older patient.

Evaluation of the anticoagulant effect and timing of the concomitant use of S-1 and warfarin

Objectives

To evaluate the effects of the timing of warfarin (WF) administration in patients with gastric cancer who received S-1 oral chemotherapy.

Methods

This retrospective chart review collected patient data including the prothrombin time international normalized ratio (PT-INR). Patients were categorized into three groups based on the timing of WF administration in relation to S-1 oral chemotherapy: group A patients received WF before S-1 chemotherapy; group B patients started WF during S-1 chemotherapy; and group C patients started WF after completing S-1 chemotherapy.

Results

A total of 21 patients with gastric cancer were included in the study; group A ( n = 8), group B ( n = 10) and group C ( n = 3). Seven patients (88%) in group A, seven (70%) in group B and all of the patients (100%) in group C had >2.5 PT-INR. There was no significant difference in the time-to-exceed 2.5 PT-INR between groups A and B.

Conclusions

These findings suggest that the timing of WF use in relation to S-1 chemotherapy might not be an important factor for PT-INR, although the low patient numbers included in the study should be taken into consideration.

Impact of capecitabine and S-1 on anticoagulant activity of warfarin in patients with gastrointestinal cancer

PURPOSE

Capecitabine and S-1 are orally administered fluoropyrimidine anticancer drugs widely used to treat gastrointestinal cancer. While anticoagulant therapy for cancer patients is recommended, many studies have shown that the effects of warfarin are enhanced by its interaction with fluoropyrimidine. We investigated the effects of capecitabine or S-1 on the anticoagulant activity of warfarin in patients coadministered both drugs.

METHODS

We retrospectively investigated the clinical features of and anticoagulant activity in nine consecutive patients who received capecitabine or S-1 in combination with warfarin from January 2008 to December 2014 at our institution. The prothrombin time international normalized ratio divided by current warfarin dosage (PT-INR/dose) was measured over time to evaluate warfarin titer in each patient.

RESULTS

Reductions in warfarin dosage were required, from 2.6 mg/day before chemotherapy to a minimum of 1.7 mg/day after chemotherapy initiation, on average. The median time until the first dosage reduction after initiation was 22 days for the capecitabine group and 43 days for the S-1 group. The median time until minimal dosage of warfarin was reached was 43 days in both groups. PT-INR/dose was elevated from 0.85 before chemotherapy to a maximum of 1.41 after its initiation. The median time until the maximal PT-INR/dose was reached was 46 days for the capecitabine group and 46.5 days for the S-1 group.

CONCLUSIONS

The anticoagulant activity of warfarin may be enhanced by coadministration with capecitabine or S-1. Close monitoring of anticoagulant activity is required to avoid a hyperfibrinolytic state due to a severe adverse interaction.

Intensity of adjuvant chemotherapy regimens and grade III-V toxicities among elderly stage III colon cancer patients

PURPOSE

The aim of this study was to provide insight in the use, intensity and toxicity of therapy with capecitabine and oxaliplatin (CAPOX) and capecitabine monotherapy (CapMono) among elderly stage III colon cancer patients treated in everyday clinical practice.

METHODS

Data from the Netherlands Cancer Registry were used. All stage III colon cancer patients aged ≥70 years diagnosed in the southeastern part between 2005 and 2012 and treated with CAPOX or CapMono were included. Differences in completion of all planned cycles, cumulative dosages and toxicity between both regimens were evaluated.

RESULTS

One hundred ninety-three patients received CAPOX and 164 patients received CapMono; 33% (n = 63) of the patients receiving CAPOX completed all planned cycles of both agents, whereas 55% (n = 90) of the patients receiving CapMono completed all planned cycles (P < 0.0001). The median cumulative dosage capecitabine was lower for patients treated with CAPOX (163,744 mg/m(2), interquartile range [IQR] 83,397-202,858 mg/m(2)) than for patients treated with CapMono (189,195 mg/m(2), IQR 111,667-228,125 mg/m(2), P = 0.0003); 54% (n = 105) of the patients treated with CAPOX developed grade III-V toxicity, whereas 38% (n = 63) of the patients treated with CapMono developed grade III-V toxicity (P = 0.0026). After adjustment for patient and tumour characteristics, CapMono was associated with a lower odds of developing grade III-V toxicity than CAPOX (odds ratio 0.54, 95% confidence interval 0.33-0.89). For patients treated with CAPOX, the most common toxicities were gastrointestinal (29%), haematological (14%), neurological (11%) and other toxicity (13%). For patients treated with CapMono, dermatological (17%), gastrointestinal (13%) and other toxicity (11%) were the most common.

CONCLUSION

CAPOX is associated with significantly more grade III-V toxicities than CapMono, which had a pronounced impact on the cumulative dosage received and completion of all planned cycles. In this light, CapMono seems preferable over CAPOX.

Tissue factor expressed by circulating cancer cell-derived microparticles drastically increases the incidence of deep vein thrombosis in mice

BACKGROUND

The risk of thrombotic complications such as deep vein thrombosis (DVT) during tumor development is well known. Tumors release into the circulation procoagulant microparticles (MPs) that can participate in thrombus formation following vessel injury. The importance of this MP tissue factor (TF) in the initiation of cancer-associated DVT remains uncertain.

OBJECTIVE

To investigate how pancreatic cancer MPs promote DVT in vivo.

METHODS

We combined a DVT mouse model in which thrombosis is induced by flow restriction in the inferior vena cava with one of subcutaneous pancreatic cancer in C57BL/6J mice. We infused high-TF and low-TF tumor MPs to determine the importance of TF in experimental cancer-associated DVT.

RESULTS

Both tumor-bearing mice and mice infused with tumor MPs subjected to 3 h of partial flow restriction developed an occlusive thrombus; fewer than one-third of the control mice did. We observed that MPs adhered to neutrophil extracellular traps (NETs), which are functionally important players during DVT, whereas neither P-selectin nor glycoprotein Ib were required for MP recruitment in DVT. The thrombotic phenotype induced by MP infusion was suppressed by hirudin, suggesting the importance of thrombin generation. TF carried by tumor MPs was essential to promote DVT, as mice infused with low-TF tumor MPs had less thrombosis than mice infused with high-TF tumor MPs.

CONCLUSIONS

TF expressed on tumor MPs contributes to the increased incidence of cancer-associated venous thrombosis in mice in vivo. These MPs may adhere to NETs formed at the site of thrombosis.

Potential cytochrome P-450 drug-drug interactions in adults with metastatic solid tumors and effect on eligibility for Phase I clinical trials

PURPOSE

Potential cytochrome P-450 (CYP) drug-drug interactions in adults with metastatic solid tumors and their effect on eligibility for Phase I clinical trials were characterized.

METHODS

This study included adult patients with metastatic solid tumors seen by a medical oncologist from January 2008 through July 2011. The medications used by these patients were identified. Each medication's potential for interacting with CYP isozymes was also characterized. Medication changes required to meet Phase I trial eligibility criteria were also reviewed.

RESULTS

Data from 1773 patients were analyzed: 1489 were not enrolled in a Phase I trial and 284 were enrolled in a Phase I trial. Polypharmacy was significantly more prevalent in the group enrolled in a Phase I trial compared with those not enrolled (95% versus 80%, p < 0.001). The majority of patients not enrolled in a Phase I trial were taking at least one CYP isozyme inhibitor (87%) and at least one CYP isozyme inducer (45%). In a separate analysis, four Phase I trials were evaluated. Of 295 screened patients, 3.2% could not enroll due to concurrent medications. Charts from 74 enrolled patients revealed 655 concurrent medications—93 medications required further review for eligibility involving 51 (69%) of patients. Of the 93 medications, 38 (41%) were stopped and 41 (44%) were changed for the study.

CONCLUSION

Polypharmacy and the use of medications that interact with CYP isoyzmes were common in adult patients with metastatic solid tumors. Patients enrolling in Phase I studies often require medication changes to meet eligibility requirements.

In vitro inhibition of CYP2C9-mediated warfarin 7-hydroxylation by iguratimod: possible mechanism of iguratimod-warfarin interaction

Iguratimod is a novel disease-modifying antirheumatic drug. A blue letter (safety advisory) for drug interaction between iguratimod and warfarin was issued by the Ministry of Health, Labour and Welfare of Japan in May 2013. Iguratimod may affect warfarin metabolism catalyzed by CYP. However, it is not clear whether iguratimod inhibits warfarin oxidation. This study was performed to investigate the effects of iguratimod on warfarin 7-hydroxylation with human liver microsomes (HLMs) and recombinant CYP enzymes. Iguratimod concentration-dependently inhibited R,S-warfarin 7-hydroxylase activity of HLMs with an IC50 value of 15.2 µM. The inhibitory effect was examined with S-warfarin and R-warfarin to determine which enantiomer was more potently inhibited by iguratimod. Iguratimod potently inhibited the S-warfarin 7-hydroxylase activity of HLMs with an IC50 value of 14.1 µM, but showed only slight inhibition of R-warfarin 7-hydroxylation. Furthermore, iguratimod inhibited the S-warfarin 7-hydroxylase activity of recombinant CYP2C9.1 (rCYP2C9.1) and rCYP2C9.3 in a concentration-dependent manner with IC50 values of 10.8 and 20.1 µM, respectively. Kinetic analysis of the inhibition of S-warfarin 7-hydroxylation by iguratimod indicated competitive-type inhibition for HLMs and rCYP2C9.1 but mixed-type inhibition for rCYP2C9.3. The Ki values for HLMs, rCYP2C9.1, and rCYP2C9.3 were 6.74, 4.23, and 14.2 µM, respectively. Iguratimod did not exert metabolism-dependent inhibition of S-warfarin 7-hydroxylation. These results indicated that iguratimod is a potent direct inhibitor of CYP2C9-mediated warfarin 7-hydroxylation and that its inhibitory effect on CYP2C9.1 was more sensitive than that on CYP2C9.3.

Venous Thromboembolism in Cancer Patients Undergoing Major Abdominal Surgery: Prevention and Management

Cancer is an important risk factor for venous thrombosis. Venous thromboembolism is one of the most common complications of cancer and the second leading cause of death in these patients. Recent research has given insight into mechanism and various risk factors in cancer patients which predispose to thromboembolism. The purpose of this review is to summarize the current knowledge on the prophylaxis, diagnosis, and management of venous thromboembolism in these patients.

Effects of patupilone on the pharmacokinetics and pharmacodynamics of warfarin in patients with advanced malignancies: a phase I clinical trial

Patupilone is a novel microtubule-targeting cytotoxic agent, which exerts its antitumor effect through microtubule stabilization. Pharmacokinetics, pharmacodynamics, and safety of warfarin when administered concomitantly with patupilone were investigated, and antitumor activity was assessed. This was a phase I, two-center, drug-drug interaction study. In the core phase of the study, treatment consisted of warfarin 20 mg orally (days 1 and 29) and patupilone 10 mg/m(2) i.v. (days 8 and 29). Patients benefiting from patupilone treatment continued treatment every 3 weeks (extension phase) until progression of disease, death, or unacceptable toxicity. Seventeen patients were treated (core phase, 17; extension, 9). The geometric mean ratios (comedication/monotherapy) for C(max) and area under the curve(0-168) of warfarin were near unity and their 90% confidence intervals were within the equivalence limits of 0.80 and 1.25. The half-life, plasma clearance, and International Normalized Ratio (INR) of warfarin were not affected by patupilone coadministration. The most common adverse events were diarrhea, nausea, vomiting, abdominal pain, anorexia, dehydration, asthenia, and peripheral neuropathy. Five (29.4%) patients experienced grade 3 study drug-related adverse events (diarrhea, 17.6%; increased INR, 11.8%; dehydration, 5.9%; and neutropenia, 5.9%). One patient with triple-negative breast cancer (estrogen receptor, progesterone receptor, and HER2/neu negative) had a partial response (35% decrease in tumor measurements by Response Evaluation Criteria in Solid Tumors), and 11 had stable disease for 6 weeks or more (≥12 weeks, 6 patients). The pharmacokinetics and pharmacodynamics of warfarin were not affected by patupilone coadministration, suggesting that patupilone has no clinically relevant effect on CYP2C9 metabolism. Patupilone showed antitumor activity in triple-negative breast cancer.

Polypharmacy in elderly patients with cancer: clinical implications and management

More and more elderly people with cancer are treated in oncology clinics worldwide every year, many of whom have comorbid disorders treated with one or more drugs. Moreover, these patients might also take self-prescribed over-the-counter drugs or complementary and alternative medicines, which they might not tell their doctor about. Initiation of chemotherapy with one or more cytotoxic or targeted agents and drugs for treatment of cancer symptoms or toxic effects related to treatment can result in polypharmacy. We examine the clinical implications of polypharmacy. Challenges for the medical teams who treat elderly patients with cancer include identification of what drugs are actually being taken by the patient, avoidance or management of any adverse effects or drug interactions, and reassessing the patient's overall treatment. We address these issues and propose practical recommendations for management of treatment for elderly patients with cancer.

Management of venous thromboembolism in patients with cancer

Patients with cancer are at increased risk of venous thromboembolism (VTE). In these patients VTE is associated with substantial morbidity and complicates the clinical management of cancer. Emerging research indicates a probable detrimental effect of VTE on cancer survival. Although VTE may develop at any stage of cancer disease, the risk of VTE is particularly high in association with three clinical settings including surgery for cancer, use of a central vein catheter (CVC) and chemotherapy. Guidelines recommend post-operative prophylaxis (for at least 7-10 days) for patients undergoing elective cancer surgery. A prolonged prophylaxis (for upto four post-operative weeks) is recommended in cancer patients at high risk for VTE. The role of antithrombotic prophylaxis in the prevention of CVC-related thrombosis remains controversial. The PROTECHT study has recently evaluated the benefit of antithrombotic prophylaxis in cancer patients receiving chemotherapy, showing a statistically significant 50% relative risk reduction in symptomatic thromboembolic events. The international guidelines currently agree in non-recommending routine prophylaxis in ambulatory patients who receive anticancer chemotherapy but suggest an individual risk-based evaluation. To better identify cancer patients at high risk for VTE, simple predictive models have been validated. Further intervention studies are currently on-going to explore the benefit of antithrombotic prophylaxis in individual high-risk groups of patients. The long-term treatment of cancer-related VTE is based on therapeutic doses of LMWH in preference to warfarin. The optimal duration of antithrombotic treatment in cancer patients remains to be fully defined.

Potential drug interactions in cancer therapy: a prevalence study using an advanced screening method

BACKGROUND

In cancer patients, drug interactions may intensify adverse events or reduce antitumour effects. We assessed the prevalence of potential drug interactions (PDIs) among ambulatory cancer patients on i.v. treatment using an advanced screening method.

PATIENTS AND METHODS

Data on drugs used for comorbidities, anticancer agents, over-the-counter (OTC) drugs, and comorbidities were collected by means of a structured interview among the patients and review of medical charts. PDIs were identified using electronic (Drug Interaction Facts software, version 4.0) and manual screening methods (peer-reviewed reports).

RESULTS

In this study, 278 patients were enrolled. We identified 348 PDIs. Of all patients, 161 (58%) had at least one PDI. Of all PDIs, 34% was classified as major and 60% as moderate. Coumarins, quinolones, antiepileptics, and hydrochlorothiazide were frequently part of a PDI. Interactions that potentially cause QT interval prolongation, gastrointestinal toxicity, and central nervous system depression were also common. In multivariate analysis, an increasing number of drugs [odds ratio (OR) = 1.4, confidence interval (CI) 1.23-1.52; P < 0.001] and the use of an OTC drug (OR = 0.56, CI 0.32-0.97; P = 0.045) were risk factors.

CONCLUSIONS

PDIs are common in patients treated for an (haemato-) oncological disease. Screening for potential interactions should take place routinely before administering chemotherapy.

Timing of expression of blood coagulation abnormality in patients treated with warfarin and s-1 concomitantly

Although S-1 is frequently used in cancer chemotherapy, the drug interaction with warfarin, an anticoagulant agent, is not fully paid attention. In the present study, we investigated retrospectively the timing of expression of blood coagulation abnormality in nine patients treated with warfarin and S-1 concomitantly. In five patients, the dose of warfarin was reduced or interrupted after concomitant use of S-1. The International Normalized Ratio (INR) was significantly increased after combination with S-1 compared with the former value. In all patients, the INR was increased in three weeks after combination with S-1. On the other hand, serum creatinine, aspartate aminotransferase, alanine aminotransferase or serum albumin was not different before and after combination with S-1. These results suggest that the careful monitoring of the blood coagulation ability is necessary in all patients receiving warfarin and S-1 concomitantly.

Adverse Interaction between Capecitabine and Warfarin Resulting in Altered Coagulation Parameters: A Review of the Literature Starting from a Case Report

Capecitabine is an orally active prodrug of fluorouracil and is extensively used as an antineoplastic agent. It is converted to 5-Fluorouracil in the liver and tumor tissues. Warfarin is an anticoagulant agent for preventing and treating venous and arterial thrombosis and embolism and is metabolized by cytochrome P450 isoenzymes in the liver. Preclinical in vitro studies using human liver microsomes report no inhibitory effects between capecitabine and substrates of cytochrome P. However, the concomitant administration of capecitabine and warfarin resulted in INR elevation in the cases previously reported in the literature. The exact mechanism of this interaction is unknown but may be related to downregulation of cytochrome P450 2C9 by capecitabine or its metabolites. We report on the possible adverse interaction between capecitabine and warfarin in a patient with metastatic breast cancer and critically review the existing literature on this topic. Physicians should be aware of adverse reactions arising from the combined use of capecitabine and warfarin. In the light of the current data, INR levels should be closely monitored in patients using these drugs together.

Polypharmacy in older adults with cancer

The definition of "polypharmacy" ranges from the use of a large number of medications; the use of potentially inappropriate medications, which can increase the risk for adverse drug events; medication underuse despite instructions to the contrary; and medication duplication. Older adults are particularly at risk because they often present with several medical conditions requiring pharmacotherapy. Cancer-related therapy adds to this risk in older adults, but few studies have been conducted in this patient population. In this review, we outline the adverse outcomes associated with polypharmacy and present polypharmacy definitions offered by the geriatrics literature. We also examine the strengths and weaknesses of these definitions and explore the relationships among these definitions and what is known about the prevalence and impact of polypharmacy.

Increased anticoagulant activity of warfarin used in combination with doxifluridine

PURPOSE

The purpose of this article is to report the first case of markedly increased anticoagulant activity of warfarin when used in combination with doxifluridine, given as a replacement for capecitabine.

METHODS

International normalized ratio (INR) of a 73-year-old female patient receiving warfarin was increased after starting chemotherapy using oral fluoropyrimidines (capecitabine or doxifluridine). Since the concomitant use of warfarin and the oral fluoropyrimidines was unavoidable in this case, the warfarin dosage was adjusted to keep INR within goal range (1.7-2.7). To evaluate the effects of the oral fluoropyrimidines on the anticoagulant activity of warfarin, the INR/Dose (warfarin dose in mg/day) was used.

RESULTS

To keep INR within goal range, the maintenance dosage of warfarin was reduced during the treatment with doxifluridine as well as capecitabine. It was finally reduced from 5 mg daily in the absence of oral fluoropyrimidines to 1.5 mg daily during the concomitant use of doxifluridine (600 mg daily). In contrast, the higher INR/Dose (1.03-1.66) was continued during the concomitant use of warfarin and doxifluridine compared with the INR/Dose before the start of chemotherapy (about 0.5). These results clearly indicate that the anticoagulant activity of warfarin was markedly increased by the concomitant use of doxifluridine as well as capecitabine.

CONCLUSIONS

It is important that physicians closely monitor anticoagulant activity in patients concomitantly receiving doxifluridine and warfarin, and appropriately adjust the dose of warfarin.

Drug interactions in oncology: how common are they?

BACKGROUND

Drug-drug interactions (DDIs) comprise an important problem in medical oncology practice. We systematically reviewed the frequency of DDIs in oncology.

METHODS

We searched PubMed for eligible articles and on-line databases for abstracts of major oncology meetings.

RESULTS

Eight studies reported on the frequency of DDIs: six evaluated the frequency of potential DDIs, while two studies reported on real DDIs, i.e. interactions that had clinical consequences. Studies of potential DDIs found that approximately one-third of patients are exposed to dangerous drug doublets, with the most common ones involving warfarin and anticonvulsants. One study of real DDIs found that 2% of hospitalized cancer patients had a DDI as the cause of admission.

CONCLUSIONS

Drug interactions comprise an important issue in oncology, with approximately one-third of ambulatory cancer patients being at risk of DDIs. Data are limited on the clinical consequences of drug interactions among cancer patients.

Pharmacology and therapeutic efficacy of capecitabine: focus on breast and colorectal cancer

Capecitabine (N -pentyloxycarbonyl-5-deoxy-5-fluorocytidine), an oral prodrug of 5-fluorouracil, has provided compelling efficacy data for the treatment of metastatic breast cancer and stage III or IV colorectal cancer, both as monotherapy and in combination regimens. The preferential conversion of capecitabine to 5-fluorouracil in neoplastic tissues renders this fluoropyrimidine particularly appealing for clinical use. The enzyme thymidine phosphorylase, which mediates the final step of the capecitabine activation pathway, is expressed in higher concentration in neoplastic than in healthy tissues. This makes capecitabine more tumor specific than other chemotherapeutic agents. Accordingly, capecitabine is generally well tolerated. In particular, the incidence of myelosuppression and alopecia is low, and the most common side effects, hand-foot syndrome and diarrhea, are usually manageable. Given its good toxicity profile, capecitabine was assessed in combination with several chemotherapeutic or biologic agents. In addition, the observation that thymidine phosphorylase is upregulated after treatment with other anticancer drugs, namely taxanes, provided a rationale for the prominent antitumor activity recently observed for the combination of capecitabine with these agents. This review provides an evidence-based update of clinical trials investigating the role of capecitabine in the treatment of breast and colorectal cancer, with special emphasis on pharmacological and safety issues that form the basis of currently used schedules.

Targeting the eicosanoid pathway in non-small-cell lung cancer

Multiple lines of evidence suggest that cyclooxygenase-2 (COX-2) upregulation is an early event in the development of non-small-cell lung cancer. Preclinical data indicate tumors with upregulation of COX-2 synthesize high levels of prostaglandin E₂ (PGE₂), which in turn are associated with increased production of proangiogenic factors and enhanced metastatic potential. These findings indicate that an increase in COX-2 expression may play a significant role in the development and growth of lung cancers and possibly with the acquisition of an invasive and metastatic phenotype. Consequently, inhibitors of COX-2 are being studied for their chemopreventative and therapeutic effects in individuals at high risk for lung cancer and patients with established cancers.

Clinically Significant Drug–Drug Interactions Between Oral Anticancer Agents and Nonanticancer Agents: Profiling and Comparison of Two Drug Compendia

Background:

Use of oral anticancer agents is gaining wide acceptance in the treatment of cancer. However, patients receiving oral therapy are at high risk for drug–drug interactions (DDIs).

Objective:

To create a drug profile for each clinically significant DDI involving selected oral anticancer agents and evaluate the agreement between 2 commonly used DDI compendia: Drug Interaction Facts (DIF) 2008 and Micromedex DRUGDEX.

Methods:

DDI profiles were developed based on primary and tertiary literature reviews. DIF 2008 and Micromedex DRUGDEX were compared to assess the consistency of listings, severity, and scientific evidence ratings of DDIs involving the oral anticancer agents that were selected. The Spearman correlation test was used to assess the correlation of the severity ratings between the 2 compendia.

Results:

A total of 184 DDIs were identified. A DDI profile was created for 40 of these that met the predetermined criteria for clinically significant interactions. The comparative assessment showed inconsistency in DDI listings (15.2% of those identified were listed in DIF only and 46.7% were listed in Micromedex only), severity ratings (Spearman correlation coefficient 0.49), and scientific evidence ratings (disagreement 25.8%).

Conclusions:

The discrepancies in DDI listing and rating systems between the compendia evaluated here reflect the need for more studies to standardize the definitions and classifications of DDIs.

Contribution of capecitabine for therapy of patients with gastroesophageal cancer: an update of recent phase III results

Background

Capecitabine, an orally administered fluoropyrimidines, is widely used in the treatment of multiple malignancies. It has been extensively evaluated in patients with gastroesophageal carcinoma. Since recent reviews have discussed phase I/II trials (Cancer 107:221–231, 2006; Drugs 67:601–610, 2007), we focus on the impact of the results of the most current phase III trials using capectiabine in the treatment of advanced gastroesophageal cancers, primarily in the first-line setting.

Methods

To find published phase III trials, Medline was searched for English-language clinical trials published from 1996 through June 2007 along with relevant abstracts presented at the American Society of Clinical Oncology, and meetings of the European Cancer Conference and European Society of Medical Oncology. Only representative trials were chosen for this manuscript.

Results

The most frequently investigated combinations are capecitabine with taxanes, platinols, and camptothecins. Recent results of a large phase III trial (REAL-2) in untreated patients with gastroesophageal cancer suggest that capecitabine is a non-inferior substitute for intravenous 5-fluorouracil. These results of REAL-2 trial are substantiated by a smaller phase III trial. Previous analysis of multiple trials had suggested that capecitabine, when combined in doses lower than 1250 mg/m² twice daily, consistently resulted in lower frequency of Grade 3 or 4 toxic effects.

Conclusions

Capecitabine provides much needed convenience to patients with gastroesophageal cancer. The recent data derived from two phase III trials confirm that capecitabine is a suitable substitute for intravenous 5-fluorouracil in patients whose swallowing is not greatly affected. Capecitabine remains a subject of further investigations in this group of patients with interest.

Capecitabine in the treatment of advanced gastric cancer

Although the role of systemic chemotherapy has been established for the treatment of advanced gastric cancer, the prognosis of these patients remains poor, with a median overall survival of less than 1 year. Based on the results of several randomized Phase III trials, 5-fluorouracil continuous infusion plus cisplatin, with or without epirubicin, has become the global reference regimen for this patient population. However, treatment with fluorouracil infusion requires either frequent hospitalizations or the use of a central venous access device, harboring potential complications. Capecitabine, a tumor-activating oral prodrug of fluorouracil, may be more advantageous in terms of patient convenience, safety and efficacy. Two recent randomized Phase III trials have shown that capecitabine could replace infusional fluorouracil in cisplatin-based regimens. Furthermore, Phase II trials have shown that many other capecitabine-based doublet or triplet chemotherapy regimens incorporating newer cytotoxic agents are active and well tolerated. Many promising biological agents are now being tested in Phase III trials, incorporating capecitabine combinations as control arms, in patients with advanced gastric cancer.

Clinical pharmacology of cancer therapies in older adults

This abbreviated review outlines the physiologic changes associated with aging, and examines how these changes may affect the pharmacokinetics and pharmacodynamics of anticancer therapies. We also provide an overview of studies that have been conducted evaluating the pharmacology of anticancer therapies in older adults, and issue a call for further research.

A phase I safety, tolerability, and pharmacokinetic study of enzastaurin combined with capecitabine in patients with advanced solid tumors

Enzastaurin, an oral inhibitor of protein kinase Cbeta, affects signal transduction associated with angiogenesis, proliferation, and survival. Capecitabine is converted to 5-fluoruracil by thymidine phosphorylase, a putative angiogenic factor. The all-oral combination of the two drugs offers the potential for targeting angiogenesis in capecitabine-sensitive tumors with nonoverlapping toxicities. Patients with advanced cancer initially received single-agent enzastaurin to achieve steady-state concentrations (cycle 1). In subsequent 21-day cycles, enzastaurin was given orally, once daily, on days 1-21 and capecitabine orally, twice daily (b.i.d.), on days 1-14 in three dose-level cohorts. Three dose-escalation cohorts were studied: cohort 1 (n=8), 350 mg of enzastaurin +capecitabine (750 mg/m2 b.i.d.); cohort 2 (n=7), enzastaurin (350 mg)+capecitabine (1000 mg/m2 b.i.d.); cohort 3 (n=12), 525-mg capsules or 500-mg enzastaurin+capecitabine (1000 mg/m2 b.i.d.). Further dose escalation was not pursued because of emerging data that enzastaurin systemic exposure did not increase at doses above 525 mg. Although a traditional toxicity-based maximum tolerated dose was not achieved, the highest dosing cohort represented a biologically relevant dose of enzastaurin, on the basis of preclinical data and correlative pharmacodynamic biomarker assays of protein kinase Cbeta inhibition in peripheral blood mononucleocytes, in combination with a standard dose of capecitabine. For the 500/525-mg dose, ratios of total enzastaurin analyte geometric means (i.e. enzastaurin alone versus enzastaurin with capecitabine) reflected a trend toward decreased enzastaurin exposure, but did not reach statistical significance. The pharmacokinetic parameters of capecitabine with enzastaurin were similar to those previously reported for single-agent capecitabine. The regimen was well tolerated, without any consistent pattern of drug-related grade 3 or grade 4 toxicities being observed. Although no objective tumor responses were documented, five patients maintained stable disease for >or=6 months (range: 6-9.7 months). The recommended phase II dose of this combination, based on the results of this study, is enzastaurin at a daily dose of 500 mg (tablet formulation) and capecitabine (1000 mg/m2, b.i.d.) on days 1-14 every 21 days. Further disease-directed studies are warranted, such as in malignancies in the treatment of which both capecitabine and inhibitors of angiogenesis have previously been benchmarked as being effective.

Capecitabine in advanced gastric cancer

Since the routine introduction of chemotherapy for advanced gastric cancer in the early 1990 s, median survival for gastric cancer has improved from 3 months, with best supportive care alone, to > 11 months in recently reported Phase III trials of triplet chemotherapy. Capecitabine is an orally-active fluoropyrimidine, which is selectively metabolised to fluorouracil in tumour cells. The combinations of platinum compounds and capecitabine have been evaluated in two recent, large, Phase III trials demonstrating non-inferiority in efficacy compared with platinum plus continuous infusion fluorouracil. In view of the convenience and flexibility of patients in adjusting dosage when encountering toxicities, capecitabine is replacing continuous infusion fluorouracil as the backbone of combination chemotherapy in advanced gastric cancer patients. Future trials evaluating biologicals are now incorporating capecitabine combinations as control arms in both advanced disease and peri-operative settings in gastric cancer.

Potential drug interactions and duplicate prescriptions among cancer patients

BACKGROUND

Cancer patients receive numerous medications, including antineoplastic agents, drugs for supportive care, and medications for comorbid illnesses. Therefore, they are at risk for drug interactions and duplicate prescribing.

METHODS

A questionnaire eliciting information on demographics and medications taken in the previous 4 weeks was given to adult outpatients receiving systemic anticancer therapy for solid tumors. The Drug Interaction Facts software, version 4.0, was used to identify potential drug interactions and to classify them by level of severity (major, moderate, or minor) and the strength of scientific evidence for them (using categories [1-5] of decreasing certainty). Summary statistics and logistic regression were used to analyze the data. All statistical tests were two-sided.

RESULTS

The survey was completed by 405 patients. We observed 276 potential drug interactions, and at least one potential interaction was identified in 109 patients (27%; 95% confidence interval [CI] = 23% to 31%). Of the potential interactions, 25 (9%) were classified as major and 211 (77%) as moderate. Nearly half (49%) of potential interactions were supported by level 1 or 2 scientific evidence. Most potential drug interactions (87%) involved non-anticancer agents such as warfarin, antihypertensive drugs, corticosteroids, and anticonvulsants, but some (n = 36, 13%) involved antineoplastic agents. In multivariable analysis, increased risk of receiving drug combinations in which there were potential drug interactions was associated with receipt of increasing numbers of drugs (odds ratio [OR] = 1.4 per additional drug, 95% CI = 1.26 to 1.58, P<.001 from the Wald chi-square test), type of medication (drugs to treat comorbid conditions versus supportive care medications only; OR = 8.6, 95% CI = 2.9 to 25, P<.001), and the presence of brain tumors. Thirty-two (8%) patients were exposed to duplicate medications, most often corticosteroids, proton pump inhibitors, or benzodiazepines.

CONCLUSION

Potential drug interactions were common among cancer patients and most often involved medications to treat comorbid conditions. Duplicate medications were infrequent.

Metastatic colorectal cancer

Metastatic colorectal cancer remains a public-health issue on a global scale. With development of a new generation of cytotoxic agents, survival has improved for patients with metastatic disease. How to maximize the benefit of chemotherapy with acceptable toxicity remains incompletely answered. Hepatic resection can provide a significant hope for long term survival, and a subset of patients might benefit from perioperative approaches. More recently, specific molecular processes have been targeted for therapeutic interventions, and encouraging results have been achieved using inhibitors of the Epidermal Growth Factor Receptor and the Vascular Endothelial Growth Factor.