A comparison of the renal function biomarkers serum creatinine, pro-enkephalin and cystatin C to predict clearance of pemetrexed

INTRODUCTION

For drugs with a narrow therapeutic window, there is a delicate balance between efficacy and toxicity, thus it is pivotal to administer the right dose from the first administration onwards. Exposure of pemetrexed, a cytotoxic drug used in lung cancer treatment, is dictated by kidney function. To facilitate optimized dosing of pemetrexed, accurate prediction of drug clearance is pivotal. Therefore, the aim of this study was to investigate the performance of the kidney function biomarkers serum creatinine, cystatin C and pro-enkephalin in terms of predicting the elimination of pemetrexed.

METHODS

We performed a population pharmacokinetic analysis using a dataset from two clinical trials containing pharmacokinetic data of pemetrexed and measurements of all three biomarkers. A three-compartment model without covariates was fitted to the data and the obtained individual empirical Bayes estimates for pemetrexed clearance were considered the "true" values (Cltrue). Subsequently, the following algorithms were tested as covariates for pemetrexed clearance: the Chronic Kidney Disease Epidemiology Collaboration equation using creatinine (CKD-EPICR), cystatin C (CKD-EPICYS), a combination of both (CKD-EPICR-CYS), pro-enkephalin as an absolute value or in a combined algorithm with age and serum creatinine, and lastly, a combination of pro-enkephalin with cystatin C.

RESULTS

The dataset consisted of 66 subjects with paired observations for all three kidney function biomarkers. Inclusion of CKD-EPICR-CYS as a covariate on pemetrexed clearance resulted in the best model fit, with the largest decrease in objective function (p < 0.00001) and explaining 35% of the total inter-individual variability in clearance. The predictive performance of the model to containing CKD-EPICR-CYS to predict pemetrexed clearance was good with a normalized root mean squared error and mean prediction error of 19.9% and 1.2%, respectively.

CONCLUSIONS

In conclusion, this study showed that the combined CKD-EPICR-CYS performs best in terms predicting pharmacokinetics of pemetrexed. Despite the hypothesized disadvantages, creatinine remains to be a suitable and readily available marker to predict pemetrexed clearance in clinical practice.

Quality Control for Microarray Experiments

Objectives: In this paper we give an overview of post-hybridization quality control methods for gene expression chips, including methods for the gene/spot level, the hybridization/chip level and the process level. We present quality control methods that can be applied after hybridization and image analysis, i.e. that use data from the chip experiment itself. Wet lab quality control steps, which should be applied before the probe is measured on a chip, are not discussed. This review is aimed towards statisticians and data analysts.

Methods: We give examples of some of the quality control measures available for spotted cDNA and Affymetrix GeneChips®, the most common chip types. As quality control measures are technology and design-dependent, we will stress on methods that have the potential to be applied platform-independently.

Results: Quality control should identify poor quality chips or hybridizations, as well as faulty measurements for individual genes/spots. Additionally, high throughput laboratories processing several tens or hundreds of microarrays per week have the need for an appropriate process control to be able to identify changes in the production process as early as possible.

Conclusion: Microarrays have become a standard research tool for biologists and medical researchers. As a consequence, there is a great need for standardized quality control, as false findings due to problem in data quality can lead to a substantial loss of resources.

Busulfan-melphalan in high-risk neuroblastoma: the 30-year experience of a single institution

High-dose chemotherapy (HDC) was investigated in high-risk neuroblastoma (HR-NBL) to reduce the risk of relapse. We report the results of the 30-year experience of a cohort of patients with HR-NBL treated with high-dose (HD) busulfan (Bu)-containing regimens. From 1980 to 2009, 215 patients aged >1 year with stage 4 NBL were treated with HD Bu-containing regimens at Gustave Roussy. These data were prospectively recorded in the Pediatric Transplantation Database. The median age at diagnosis was 40 months (12-218 months). All patients had a stage 4 neuroblastoma. NMYC amplification was displayed in 24% of the tumors. The hematopoietic support consisted of bone marrow or PBSCs in 46% and 49% of patients, respectively. The 5-year event-free survival and overall survival rates of the whole cohort were 35.1% and 40%, respectively. Age at diagnosis, bone marrow involvement and tumor response after induction chemotherapy were significant prognostic factors. Toxicity was manageable and decreased over time, owing to both PBSC administration and better supportive care. Based on this experience, HD Bu-melphalan (Mel) has been implemented in Europe and compared with Carboplatin-Etoposide-Mel in the European SIOP Neuroblastoma (SIOPEN)/HR-NBL randomized protocol. It has now become the standard HDC in the SIOPEN HR strategy.

Magnetism of the chromium thio-spinels Fe1-xCuxCr2S4 studied using muon spin rotation and relaxation

Powder samples of Fe1-xCuxCr2S4 with x = 0,0.2,0.5,0.8 were studied, between 5 and 300 K. The results reveal that for x < 1, the magnetic order in the series is more varied than the simple collinear ferrimagnetic structure traditionally assumed to exist everywhere from the Curie point to T → 0. In FeCr2S4 several ordered magnetic phases are present, with the ground state likely to have an incommensurate cone-like helical structure. Fe0.8Cu0.2Cr2S4 is the compound for which simple collinear ferrimagnetism is best developed. In Fe0.5Cu0.5Cr2S4 the ferrimagnetic spin structure is not stable, causing spin reorientation around 90 K. In Fe0.2Cu0.8Cr2S4 the ferrimagnetic structure is at low temperatures considerably distorted locally, but with rising temperature this disorder shows a rapid reduction, coupled to increased spin fluctuation rates. In summary, the present data show that the changes induced by the replacement of Fe by Cu have more profound influences on the magnetic properties of the Fe1-xCuxCr2S4 compounds than merely a shift of Curie temperature, saturation magnetization and internal field magnitude.

Procalcitonin guidance and reduction of antibiotic use in acute respiratory tract infection

Increasing worldwide development of antimicrobial resistance and the association of resistance development and antibiotic overuse make it necessary to seek strategies for safely reducing antibiotic use and selection pressure. In a first step, in a non-interventional study, the antibiotic prescription rates, initial procalcitonin (PCT) levels and outcome of 702 patients presenting with acute respiratory infection at 45 primary care physicians were observed. The second part was a randomised controlled non-inferiority trial comparing standard care with PCT-guided antimicrobial treatment in 550 patients in the same setting. Antibiotics were recommended at a PCT threshold of 0.25 ng·mL(-1). Clinical overruling was permitted. The primary end-point for non-inferiority was number of days with significant health impairment after 14 days. Antibiotics were prescribed in 30.3% of enrolled patients in the non-interventional study. In the interventional study, 36.7% of patients in the control group received antibiotics as compared to 21.5% in the PCT-guided group (41.6% reduction). In the modified intention-to-treat analysis, the numbers of days with significant health impairment were similar (mean 9.04 versus 9.00 for PCT-guided and control group, respectively; difference 0.04; 95% confidence interval -0.73-0.81). This was also true after adjusting for the most important confounders. In the PCT group, advice was overruled in 36 cases. There was no significant difference in primary end-point when comparing the PCT group treated as advised, the overruled PCT group and the control group (9.008 versus 9.250 versus 9.000 days; p = 0.9605). A simple one-point PCT measurement for guiding decisions on antibiotic treatment is non-inferior to standard treatment in terms of safety, and effectively reduced the antibiotic treatment rate by 41.6%.

Low temperature incommensurately modulated and noncollinear spin structure in FeCr2S4

FeCr(2)S(4) orders magnetically at T(N)≈ 170 K. According to neutron diffraction, the ordered state down to 4.2 K is a simple collinear ferrimagnet maintaining the cubic spinel structure. Later studies, however, claimed trigonal distortions below ∼ 60 K coupled to the formation of a spin glass type ground state. To obtain further insight, muon spin rotation/relaxation (μSR) spectroscopy was carried out between 5 and 200 K together with new (57)Fe Mössbauer measurements. Below ∼ 50 K, our data point to the formation of an incommensurately modulated noncollinear spin arrangement like a helical spin structure. Above 50 K, the spectra are compatible with collinear ferrimagnetism, albeit with a substantial spin disorder on the scale of a few lattice constants. These spin lattice distortions become very large at 150 K and the magnetic state is now better characterized as consisting of rapidly fluctuating short-range ordered spins. The Néel transition is of second order, but ill defined, extending over a range of ∼ 10 K. The Mössbauer data around 10 K confirm the onset of orbital freezing and are also compatible with the noncollinear order of iron. The absence of a major change in the quadrupole interaction around 50 K renders the distortion of crystal symmetry to be small.

Ovarian function after high-dose chemotherapy in childhood: Risk factors for developing partial ovarian failure and how to identify them early

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Background: During the last 30 years, polychemotherapies, surgery and radiotherapy have been established as standard therapies for treating pediatric cancers thus leading to a significant improvement in terms of 5-year-overall-survival which is now around 70% among children and adolescents. On the other hand, these treatments cause severe sequelae such as ovarian failure (OF) in young girls leading to a premature menopause and infertility. Methods: 29 patients treated at the Institute Gustave Roussy (Villejuif, France) have been investigated in an attempt to find biological and/or clinical markers, and imaging predictive of a partial ovarian insufficiency leading to an early menopause. Eligibility criteria: age >12 years at time of analysis; peripheral stem cell graft between 2–20 years; high dose chemotherapy. Results: 23/29 were eligible for this analysis (6 withdrawn due to oral contraception). 13/23 patients (56.5%) show no clinical evidence of ovarian treatment-related toxicity with a 13 years median time to transplant. 10/23 (43.5%) have complete ovarian insufficiency, among whom the majority have already received substitution hormone therapy (SHT). Out of 75% of pre-pubescent patients at transplant, only 2 have OF. All patients grafted at puberty (15.3 years) have high-dose chemotherapy-related immediate or definitive OF. Thiotepa >900mg/mq is castrating (odds ratio-10.1; p-0.04). Dosages of anti-müllerian hormone (AMH) collapses in patients with IO (p=0.002). Mensed patients have lower AMH dosages compared to normal population (p=2.10-e9) as for antral follicule count (>2mm). Conclusions: 1) 13/23 patients show no evidence of OF. 2) Main risk factors of OF: age ≥ 12 years; post pubertal status; thiotepa >900 mg/m2 (OR=10.1 and p=0.04). 3) Despite normal menses, many women who underwent high dose chemotherapy exhibit low AMH and Inhibine B levels and low count of follicles at a young age. These are possible markers of ovarian depletion. Cryopreservation of the ovarian cortex should be proposed to patients grafted due to a cancer independently of the age at which they have undergone high-dose chemotherapy.

No significant financial relationships to disclose.

A writing workshop for children with cancer

We present and comment on several short texts written in a writing workshop by children and adolescents treated for cancer. In addition to the obvious themes, the patients communicate the intense elements of the experience they are going through, including fear of injections, fear of not being cured, revolt, hope and a feeling of unreality, and raise the question "Why?". They are proud to express their feelings, thoughts and creativity, and relieved to be able show that they remain themselves. This can help them maintain or regain confidence in themselves and in the ability of their parents and medical staff to understand them. We consider their pleasure, their parents' and caregivers' reactions and the quality of their work as it relates to their age, academic level, cultural environment and cognitive capacities. These examples may help to inform physicians and nurses about how they perceive patients (children or adults) and their needs and abilities, and thereby improve the quality of the relationship.

Risk factors for hepatic veno-occlusive disease: a retrospective unicentric study in 116 children autografted after a high-dose BU-thiotepa regimen

At our Institute, during the last decade, the incidence of hepatic veno-occlusive disease (HVOD) appears to be on the increase among pediatric patients treated with BU-thiotepa (BU-TTP)-conditioning regimen. We thus performed a retrospective analysis to identify the risk factors for HVOD, which could explain such a change. In total, 116 patients treated at Institut Gustave Roussy, between May 1998 and December 2005 were eligible for this study having received BU-TTP as their first high-dose chemotherapy regimen, followed by autologous hematopoietic SCT (AHSCT). According to McDonald's clinical criteria, HVOD was diagnosed in 31% of these children. Demographic, clinical, biological and therapeutic parameters were evaluated in uni- and multivariate analyses that showed a significant correlation between previous carboplatin therapy and risk of developing post transplant HVOD (P=0.028). Comparable results were found for etoposide (P=0.048). In addition, a correlation between HVOD and risk of post transplant death was linked to its association with other types of organ failure (P=0.029). This study demonstrates that previous VPCARBO administration in conventional chemotherapy significantly increases the risk of HVOD among brain tumor patients later consolidated with BU-TTP followed by AHSCT.