Digital breast tomosynthesis plus synthesised images versus standard full-field digital mammography in population-based screening (TOSYMA): protocol of a randomised controlled trial

INTRODUCTION

Development of digital breast tomosynthesis (DBT) provides a technology that generates three-dimensional data sets, thus reducing the pitfalls of overlapping breast tissue. Observational studies suggest that the combination of two-dimensional (2D) digital mammography and DBT increases diagnostic accuracy. However, because of duplicate exposure, this comes at the cost of an augmented radiation dose. This undesired adverse impact can be avoided by using synthesised 2D images reconstructed from the DBT data (s2D).We designed a diagnostic superiority trial on a high level of evidence with the aim of providing a comparison of screening efficacy parameters resulting from DBT+s2D versus the current screening standard 2D full-field digital mammography (FFDM) in a multicentre and multivendor setting on the basis of the quality-controlled, population-based, biennial mammography screening programme in Germany.

METHODS AND ANALYSIS

80 000 women in the eligible age 50-69 years attending the routine mammography screening programme and willing to participate in the TOSYMA trial will be assigned by 1:1 randomisation to either the intervention arm (DBT+s2D) or the control arm (FFDM) during a 12-month recruitment period in screening units of North Rhine-Westphalia and Lower Saxony. State cancer registries will provide the follow-up of interval cancers.Primary endpoints are the detection rate of invasive breast cancers at screening examination and the cumulative incidence of interval cancers in the 2 years after a negative examination. Secondary endpoints are the detection rate of ductal carcinoma in situ and of tumour size T1, the recall rate for assessment, the positive predictive value of recall and the cumulative 12-month incidence of interval cancers. An adaptive statistical design with one interim analysis provides the option to modify the design.

ETHICS AND DISSEMINATION

This protocol has been approved by the local medical ethical committee (2016-132-f-S). Results will be submitted to international peer-reviewed journals.

TRIAL REGISTRATION

NCT03377036; Pre-results.

Pharmacokinetic and pharmacodynamic study of doxorubicin in children with cancer: results of a "European Pediatric Oncology Off-patents Medicines Consortium" trial

Purpose

Doxorubicin is a key component in many pediatric oncology treatment regimens; still pharmacology data on which current dosing regimens are based are very limited.

Methods

We conducted a multinational pharmacokinetic study investigating age dependency of doxorubicin metabolism and elimination in children with cancer. One hundred and one patients treated with doxorubicin according to a cancer-specific national or European therapeutic trial were recruited. Doses of doxorubicin ranged from 10.4 to 57.7 mg/m². Blood samples for measurement of doxorubicin and its metabolite doxorubicinol were collected after two administrations, with five samples collected in children <3 years and eight in children ≥3 years. A population pharmacokinetic approach was used for analysis, including pharmacogenetic covariates. Natriuretic peptides and cardiac troponins were measured to evaluate their role as early indicators of cardiotoxicity.

Results

Age dependence of doxorubicin clearance was demonstrated, with children less than 3 years having a statistically significant lower clearance (21.1 ± 5.8 l/h/m²) than older children (26.6 ± 6.7 l/h/m²) (p = 0.0004) after correcting for body surface area. No effect of the investigated genetic polymorphisms on the pharmacokinetics could be observed. Although natriuretic peptides were transiently elevated after each doxorubicin administration and troponin levels increased with increasing doxorubicin exposure, only limited correlation could be observed between their blood levels and doxorubicin pharmacokinetics.

Conclusion

In the European framework of funding and regulatory support, an add-on study to existing therapeutic trials was developed. The pediatric need concerning missing PK data could be addressed with limited burden for the patients. Empirically used dose adaptations for infants were generally found to be justified based on our PK analyses.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3174-8) contains supplementary material, which is available to authorized users.

Abstract 4625: Age dependence of doxorubicin pharmacokinetics in pediatric cancer patients; results of an FP7-funded clinical study

Doxorubicin is a key component of a number of treatment regimens used in paediatric oncology, despite the very limited pharmacology data on which current dosing regimens are based. We conducted a multicentre, multinational phase II pharmacokinetic study investigating age-dependency in the clearance of doxorubicin in children with solid tumours and leukaemia. The study was funded under the Framework Program 7 of the European Commission. 101 patients treated with doxorubicin according to a tumour-specific national or European therapeutic trial were recruited to the study, with a particular focus on children less than 3 years. Absolute doses of doxorubicin ranged from 2.4 to 57 mg, administered, with infusion durations ranging from 0.25 to 24 hours. Samples were collected after 2 administrations, with 5 samples collected in children &lt;3yrs and 8 samples in children ≥3yrs. Doxorubicin and its major metabolite doxorubicinol were measured in plasma using a validated HPLC-fluorescence assay with a limit of quantification of 2 μg/L for each analyte. Markers such as troponin T and natriuretic peptides were measured to evaluate as clinical indicators of cardiotoxicity. Data were analysed using a population pharmacokinetic approach, including pharmacogenetic covariates.

Data were available from all but 5 patients, with samples lost due to withdrawn consent, analytical issues or sample stability related to sample transport.

A three compartment model was sufficient to characterize the pharmacokinetics of doxorubicin, with a further compartment to describe those of the major metabolite doxorubicinol. All parameters of the population model were scaled to body surface area. Age dependence of doxorubicin clearance was demonstrated, with children less than 3 years having a lower clearance (21.1±5.8 l/h/m2) than older children (26.6±6.7 l/h/m2) (p=0.0004), even after correcting for body weight. No other patient-related covariate, including liver function, was found to influence the parameters of the model. While the model provided a good fit to the doxorubicinol data, no covariate was identified which influenced the parameters of the metabolite model. Pharmacogenetic variants, including those in transporters and drug metabolizing enzymes, had little influence on pharmacokinetic parameters. Likewise, pharmacokinetics had only limited impact on markers of cardiotoxicity such as troponins or on measured cardiac function.

This study yields new pharmacokinetic data on doxorubicin pharmacokinetics in very young patients, suggesting that lower doses may be appropriate in children less than 3 years. The data presented her may be useful for refining dosage regimens in this patient group.

Citation Format: Alan V. Boddy, Nicolas Andre, Gianni Bisogno, Joachim Boos, Maurizio D'Incalci, Nina Kontny, Miriam Krischke, Swantje Voeller, Georg Hempel. Age dependence of doxorubicin pharmacokinetics in pediatric cancer patients; results of an FP7-funded clinical study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4625. doi:10.1158/1538-7445.AM2014-4625

Sources of preanalytical error in pharmacokinetic analyses - focus on intravenous drug administration and collection of blood samples

INTRODUCTION

Pharmacokinetic (PK) studies for long-established drugs are generally performed outside the well-standardized settings of pharmaceutical industry trials. Instead, such studies are usually performed within daily clinical practice of hospitals.

AREAS COVERED

This article describes aspects of intravenous (i.v.) drug administration and blood sampling that contribute to potential sources of preanalytical errors for PK investigations. Parameters that bias determination of start and end time of i.v. infusions, as well as consistent rate of drug delivery, are discussed. Causes for drug loss in the infusion device, including adsorption and insufficient flushing, are outlined. The advantages and disadvantages of different blood sampling techniques are reviewed, with an emphasis on pediatric studies.

EXPERT OPINION

For PK studies that are integrated into the general hospital routine, a variety of potential sources of error exist. Potential pitfalls depend on the specific drug and trial characteristics and they must be anticipated and discussed in advance. Working procedures need to be developed that address the anticipated problems and in detail describe procedures that need compliance between bed and bench.

Abstract 2219: The European Paediatric Oncology off-patent medicines Consortium (EPOC) pharmacokinetic/pharmacodynamic study of doxorubicin

Background: Doxorubicin is a key component of a number of treatment regimens used in paediatric oncology despite the very limited pharmacology data on which current dosing regimens are based. In recognition of this, doxorubicin was included on the EMA priority list for paediatric off-patent medicines for which more information was required, particularly on pharmacokinetics.

Methods: The EPOC consortium, with collaborators in the UK, France, Germany and Italy, performs paediatric oncology pharmacology clinical trials. This study is a multicentre, multinational phase II pharmacokinetic study investigating age-dependency in the clearance of doxorubicin in children with solid tumours and leukaemia. All patients are being treated according to a tumour-specific national or European therapeutic trial. The aim was to recruit 100 patients, with a particular focus on children less than 3 years. The plasma levels of markers such as troponin T, are being measured to evaluate their use as clinical markers for cardiotoxicity. Data is being analysed using a population pharmacokinetic approach and the impact of pharmacogenetics is being investigated.

Results: The study has been open to recruitment in 20 clinical centres across the four participating countries. The target 100 patients have been recruited from all the contributing study protocols, with 26 patients less than 3 years. Of these 26 patients, 5 patients are less than 1 year. An interim pharmacokinetic analysis has been performed on the data from the first 31 patients. The results of the analysis are consistent with the primary aims of the overall study.

Conclusion: The data generated during this study should provide comparative data on the age-dependent pharmacokinetics and pharmacogenetics of doxorubicin. The results will contribute to optimising the safe use of doxorubicin in children with cancer.

Acknowledgements: Study funded under the seventh framework programme of the European Commission (FP7)

Citation Format: Alan V. Boddy, Alison J. Steel, Joachim Boos, Miriam Krischke, Nicolas Andre, Gianni Bisogno, Georg Hempel, Gerlind Bode, Maurizio D'Incalci, Nina Kontny. The European Paediatric Oncology off-patent medicines Consortium (EPOC) pharmacokinetic/pharmacodynamic study of doxorubicin. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2219. doi:10.1158/1538-7445.AM2013-2219

Population pharmacokinetics of doxorubicin: establishment of a NONMEM model for adults and children older than 3 years

PURPOSE

The aim of the current investigation was to develop a population pharmacokinetic model for doxorubicin and doxorubicinol that could provide improved estimated values for the pharmacokinetic parameters clearance of doxorubicin, volume of distribution of the central compartment, clearance of doxorubicinol and volume of distribution of the metabolite compartment for adults and children older than 3 years. A further aim was to investigate the potential influence of the covariates body surface area, body weight, body height, age, body mass index, sex and lean body mass on the pharmacokinetic parameters.

METHODS

Three different datasets, two containing data from adults and one containing data from adults and children, were merged and the combined dataset was analysed retrospectively. In total, the combined dataset contained 934 doxorubicin and 935 doxorubicinol plasma concentrations from 82 patients [64 adults and 18 children (<18 years)]. With this combined dataset, a population pharmacokinetic model was developed, using NONMEM(®) 7.2 and a predefined model-building strategy. Different structural models, error models and estimation methods were tested, and the inter-individual and the inter-occasion variability (variability between separate (two or three) doxorubicin infusions) were tested. Using a subset of 52 patients, the influence of different covariates on the pharmacokinetic parameters was investigated. The pharmacokinetic parameter estimates obtained from doxorubicin concentrations with the best model were fixed, and an additional compartment for doxorubicinol was added to the model. With the final model for both substances, a potential age dependency and body mass index dependency of the clearance of doxorubicin and doxorubicinol as well as of the volumes of distribution of the central and the metabolite compartment were evaluated.

RESULTS

A four-compartment model best described the doxorubicin and doxorubicinol data of the combined dataset. This model included a proportional residual error model and an inter-individual variability on the clearance of doxorubicin, on the inter-compartmental clearances of the peripheral compartments, on the clearance of doxorubicinol and on the volumes of distribution of the central, one peripheral and the metabolite compartment. Furthermore, the body surface area as covariate on all pharmacokinetic parameters and an inter-occasion variability for the clearance of doxorubicin and the volume of distribution of the central compartment were incorporated in the model. For a patient with the body surface area of 1.8 m², the clearance of doxorubicin was 53.3 L/h (inter-individual variability 31%, inter-occasion variability 13%) and the volume of distribution of the central compartment was 17.7 L (inter-individual variability 19%, inter-occasion variability 21%), respectively. The residual variability of the model was 22% for doxorubicin and 26% for doxorubicinol. The clearance of doxorubicinol was estimated at 44 L/h (inter-individual variability 50%) and the volume of distribution of the metabolite compartment at 1,150 L (inter-individual variability 57%). The evaluation of a possible age dependency and body mass index dependency showed a trend to a smaller volume of distribution of the central compartment (normalised to the body surface area) and a higher volume of distribution of the metabolite compartment (normalised to the body weight) in younger patients.

CONCLUSIONS

A four-compartment NONMEM(®) model for doxorubicin and doxorubicinol adequately described the plasma concentrations in adults and children (>3 years). No pronounced effects of age on the clearance of doxorubicin or doxorubicinol were found, and the analysis did not support the modification of the dosing strategies presently used in children and adults.

Dictyostelium Dock180-related RacGEFs regulate the actin cytoskeleton during cell motility

Cell motility of amoeboid cells is mediated by localized F-actin polymerization that drives the extension of membrane protrusions to promote forward movements. We show that deletion of either of two members of the Dictyostelium Dock180 family of RacGEFs, DockA and DockD, causes decreased speed of chemotaxing cells. The phenotype is enhanced in the double mutant and expression of DockA or DockD complements the reduced speed of randomly moving DockD null cells' phenotype, suggesting that DockA and DockD are likely to act redundantly and to have similar functions in regulating cell movement. In this regard, we find that overexpressing DockD causes increased cell speed by enhancing F-actin polymerization at the sites of pseudopod extension. DockD localizes to the cell cortex upon chemoattractant stimulation and at the leading edge of migrating cells and this localization is dependent on PI3K activity, suggesting that DockD might be part of the pathway that links PtdIns(3,4,5)P(3) production to F-actin polymerization. Using a proteomic approach, we found that DdELMO1 is associated with DockD and that Rac1A and RacC are possible in vivo DockD substrates. In conclusion, our work provides a further understanding of how cell motility is controlled and provides evidence that the molecular mechanism underlying Dock180-related protein function is evolutionarily conserved.

Tyrosine phosphatase inhibition induces loss of blood–brain barrier integrity by matrix metalloproteinase-dependent and -independent pathways

Tight junctions between endothelial cells of brain capillaries form the structural basis of the blood-brain barrier (BBB), which controls the exchange of molecules between blood and CNS. Regulation of cellular barrier permeability is a vital and complex process involving intracellular signalling and rearrangement of tight junction proteins. We have analysed the impact of tyrosine phosphatase inhibition on tight junction proteins and endothelial barrier integrity in a primary cell culture model based on porcine brain capillary endothelial cells (PBCEC) that closely mimics the BBB in vitro. The tyrosine phosphatase inhibitor phenylarsine oxide (PAO) induced increased matrix metalloproteinase (MMP) activity, which was paralleled by severe disruption of cell-cell contacts and proteolysis of the tight junction protein occludin. ZO-1 and claudin-5 were not affected. Under these conditions, the transendothelial electrical resistance (TEER) was markedly reduced. PAO-induced occludin proteolysis could be prevented by different MMP inhibitors. Pervanadate (PV) reduced the TEER similar to PAO, but did not increase MMP activity. Cell-cell contacts of PV-treated cells appeared unaffected, and occludin proteolysis did not occur. Our results suggest that tyrosine phosphatase inhibition can influence barrier properties independent of, but also correlated to MMPs. Evidence is given for a role of MMPs in endothelial tight junction regulation at the BBB in particular and probably at tight junctions (TJs) in general.