Potential clinical impact of taking multiple blood samples for research studies in paediatric oncology: how much do we really know?

Pediatric biobanks to enhance clinical and translational research for children

Including children in biomedical research is an argument for continual reflection and practice refinement from an ethical and legal standpoint. Indeed, as children reach adulthood, a reconsent method should be used, and data connected with samples should ideally be updated based on the children's growth and long-term results. Furthermore, because most pediatric disorders are uncommon, children's research initiatives should conform to standard operating procedures (SOPs) set by worldwide scientific organizations for successfully sharing data and samples. Here, we examine how pediatric biobanks can help address some challenges to improve biomedical research for children. Indeed, modern biobanks are evolving as complex research platforms with specialized employees, dedicated spaces, information technologies services (ITS), and ethical and legal expertise. In the case of research for children, biobanks can collaborate with scientific networks (i.e., BBMRI-ERIC) and provide the collection, storage, and distribution of biosamples in agreement with international standard procedures (ISO-20387). Close collaboration among biobanks provides shared avenues for maximizing scarce biological samples, which is required to promote the translation of scientific breakthroughs for developing clinical care and health policies tailored to the pediatric population. Moreover, biobanks, through their science communication and dissemination activities (i.e., European Biobank Week), may be helpful for children to understand what it means to be engaged in a research study, allowing them to see it as a pleasant, useful, and empowering experience. Additionally, biobanks can notify each participant about which projects have been accomplished (i.e., through their websites, social media networks, etc.); they can facilitate future reconsent procedures and update sample-associated data based on the children's growth. Finally, because of the increasing interest from public and commercial organizations in research efforts that include the sharing and reuse of health data, pediatric biobanks have a crucial role in this context. Consequently, they could benefit from funding opportunities for sustaining research activities even regarding rare pediatric disorders.  Conclusion: Pediatric biobanks are helpful for providing biological material for research purposes, addressing ethical and legal issues (i.e. data protection, consent, etc.), and providing control samples from healthy children of various ages and from different geographical regions and ethnicities. Therefore, it is vital to encourage and maintain children's engagement in medical research programs and biobanking activities, especially as children become adults, and reconsent procedures must be applied. What is Known: • Biobanks are critical research infrastructures for medical research, especially in the era of "omic" science. However, in light of their fragility and rights children's participation in biobanking and medical research programs is a complex argument of continuous debate in scientific literature. What is New: • We propose a review of the literature on pediatric biobanks with a particular focus on oncological biobanks. The main current limitations and challenges for pediatric biobanks are presented and possible solutions are discussed.

Blood draws up to 3% of blood volume in clinical trials are safe in children

Aim

Recommendations for maximum blood draw in children range from 1 to 5% despite limited evidence. The aim of the study was to assess the safety of blood draws in children aged six months to 12 years targeting volumes of 3% of total blood volume.

Methods

Children who experienced three‐monthly blood draws during participation in one of three investigators initiated clinical trials conducted in our institution were examined. In total, 629 venous blood draws were performed in 141 children. Adverse events and blood counts were assessed.

Results

Overall, 608 adverse events were reported. None of these included symptoms that reflected concerns on blood draw volumes or frequency. Anaemia and red cell or haemoglobin measurements outside the normal age range were not observed. A reduction in haemoglobin, haematocrit, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and mean corpuscular volume was noted in children participating in one of the three trials analysed.

Conclusion

Regular blood draws of up to 3% of total blood volume were not associated with signs of anaemia or hypovolaemia in young children. We suggest that the European recommendations be revised for clinical studies in which children are not exposed to treatments that are associated with anaemia risk.

Investigating the Experiences of Childhood Cancer Patients and Parents Participating in Optional Nontherapeutic Clinical Research Studies in the UK

BACKGROUND

While the majority of childhood cancer clinical trials are treatment related, additional optional research investigations may be carried out that do not directly impact on treatment. It is essential that these studies are conducted ethically and that the experiences of families participating in these studies are as positive as possible.

METHODS

A questionnaire study was carried out to investigate the key factors that influence why families choose to participate in optional nontherapeutic research studies, the level of understanding of the trials involved, and the experiences of participation.

RESULTS

A total of 100 participants from six UK centers were studied; 77 parents, 10 patients >16 years, and 13 patients aged 8-15 years. Ninety-seven percent of parents and 90% of patients felt that information provided prior to study consent was of the right length, with 52% of parents and 65% of patients fully understanding the information provided. Seventy-four percent of parents participated in research studies in order to "do something important", while 74% of patients participated "to help medical staff". Encouragingly, <5% of participants felt that their clinical care would be negatively affected if they did not participate. Positive aspects of participation included a perception of increased attention from medical staff. Negative aspects included spending longer periods in hospital and the requirement for additional blood samples. Ninety-six percent of parents and 87% of patients would participate in future studies.

CONCLUSIONS

The study provides an insight into the views of childhood cancer patients and their parents participating in nontherapeutic clinical research studies. Overwhelmingly, the findings suggest that participation is seen as a positive experience.

Severe anaemia associated with Plasmodium falciparum infection in children: consequences for additional blood sampling for research

BACKGROUND

Plasmodium falciparum infection may cause severe anaemia, particularly in children. When planning a diagnostic study on children suspected of severe malaria in sub-Saharan Africa, it was questioned how much blood could be safely sampled; intended blood volumes (blood cultures and EDTA blood) were 6 mL (children aged <6 years) and 10 mL (6-12 years). A previous review [Bull World Health Organ. 89: 46-53. 2011] recommended not to exceed 3.8 % of total blood volume (TBV). In a simulation exercise using data of children previously enrolled in a study about severe malaria and bacteraemia in Burkina Faso, the impact of this 3.8 % safety guideline was evaluated.

METHODS

For a total of 666 children aged >2 months to <12 years, data of age, weight and haemoglobin value (Hb) were available. For each child, the estimated TBV (TBVe) (mL) was calculated by multiplying the body weight (kg) by the factor 80 (ml/kg). Next, TBVe was corrected for the degree of anaemia to obtain the functional TBV (TBVf). The correction factor consisted of the rate 'Hb of the child divided by the reference Hb'; both the lowest ('best case') and highest ('worst case') reference Hb values were used. Next, the exact volume that a 3.8 % proportion of this TBVf would present was calculated and this volume was compared to the blood volumes that were intended to be sampled.

RESULTS

When applied to the Burkina Faso cohort, the simulation exercise pointed out that in 5.3 % (best case) and 11.4 % (worst case) of children the blood volume intended to be sampled would exceed the volume as defined by the 3.8 % safety guideline. Highest proportions would be in the age groups 2-6 months (19.0 %; worst scenario) and 6 months-2 years (15.7 %; worst case scenario). A positive rapid diagnostic test for P. falciparum was associated with an increased risk of violating the safety guideline in the worst case scenario (p = 0.016).

CONCLUSIONS

Blood sampling in children for research in P. falciparum endemic settings may easily violate the proposed safety guideline when applied to TBVf. Ethical committees and researchers should be wary of this and take appropriate precautions.

Recommendations and evidence for reporting items in pediatric clinical trial protocols and reports: two systematic reviews

BACKGROUND

Complete and transparent reporting of clinical trial protocols and reports ensures that these documents are useful to all stakeholders, that bias is minimized, and that the research is not wasted. However, current studies repeatedly conclude that pediatric trial protocols and reports are not appropriately reported. Guidelines like SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) and CONSORT (Consolidated Standards of Reporting Trials) may improve reporting, but do not offer guidance on issues unique to pediatric trials. This paper reports two systematic reviews conducted to build the evidence base for the development of pediatric reporting guideline extensions: 1) SPIRIT-Children (SPIRIT-C) for pediatric trial protocols, and 2) CONSORT-Children (CONSORT-C) for pediatric trial reports.

METHOD

MEDLINE, the Cochrane Methodology Register, and reference lists of included studies were searched. Publications of any type were eligible if they included explicit recommendations or empirical evidence for the reporting of potential items in a pediatric protocol (SPIRIT-C systematic review) or trial report (CONSORT-C systematic review). Study characteristics, recommendations and evidence for pediatric extension items were extracted. Recurrent themes in the recommendations and evidence were identified and synthesized. All steps were conducted by two reviewers.

RESULTS

For the SPIRIT-C and CONSORT-C systematic reviews 366 and 429 publications were included, respectively. Recommendations were identified for 48 of 50 original reporting items and sub-items from SPIRIT, 15 of 20 potential SPIRIT-C reporting items, all 37 original CONSORT items and sub-items, and 16 of 22 potential CONSORT-C reporting items. The following overarching themes of evidence to support or refute the utility of reporting items were identified: transparency; reproducibility; interpretability; usefulness; internal validity; external validity; reporting bias; publication bias; accountability; scientific soundness; and research ethics.

CONCLUSION

These systematic reviews are the first to systematically gather evidence and recommendations for the reporting of specific items in pediatric protocols and trials. They provide useful and translatable evidence on which to build pediatric extensions to the SPIRIT and CONSORT reporting guidelines. The resulting SPIRIT-C and CONSORT-C will provide guidance to the authors of pediatric protocols and reports, respectively, helping to alleviate concerns of inappropriate and inconsistent reporting, and reduce research waste.

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.

Variation in prescribing patterns and therapeutic drug monitoring of intravenous busulfan in pediatric hematopoietic cell transplant recipients

Personalizing intravenous (IV) busulfan doses in children using therapeutic drug monitoring (TDM) is an integral component of hematopoietic cell transplant. The authors sought to characterize initial dosing and TDM of IV busulfan, along with factors associated with busulfan clearance, in 729 children who underwent busulfan TDM from December 2005 to December 2008. The initial IV busulfan dose in children weighing ≤12 kg ranged 4.8-fold, with only 19% prescribed the package insert dose of 1.1 mg/kg. In those children weighing >12 kg, the initial dose ranged 5.4-fold, and 79% were prescribed the package insert dose. The initial busulfan dose achieved the target exposure in only 24.3% of children. A wide range of busulfan exposures were targeted for children with the same disease (eg, 39 target busulfan exposures for the 264 children diagnosed with acute myeloid leukemia). Considerable heterogeneity exists regarding when TDM is conducted and the number of pharmacokinetic samples obtained. Busulfan clearance varied by age and dosing frequency but not by underlying disease. The authors- group is currently evaluating how using population pharmacokinetics to optimize initial busulfan dose and TDM (eg, limited sampling schedule in conjunction with maximum a posteriori Bayesian estimation) may affect clinical outcomes in children.

Chemotherapy in newborns and preterm babies

The determination of appropriate dosing regimens for the treatment of infants and very young children with cancer represents a major challenge in paediatric oncology. Whereas dose reductions are commonplace for many chemotherapeutics in this patient group, the appropriateness of dose reductions for drugs is unclear when the limited number of published studies reporting on pharmacokinetics in infant patient populations are considered. Developmental physiological changes, potentially impacting significantly on drug disposition, occur throughout childhood, with a number of important changes observed within the first few weeks from birth. The current review focuses on the developmental physiology of preterm babies and infants and the potential impact of physiological changes on drug disposition, clinical response and toxicity. Dose reductions for a number of important anticancer drugs are compared between tumour types and clinical protocols. Where data exist, differences in pharmacokinetics between infants and older children are highlighted. In addition, the impact of confounding factors relating to the availability of appropriate drug formulations and ethical challenges concerning the conduct of clinical pharmacology studies in infant patient populations are addressed. As many currently used drugs are highly likely to be important in the treatment of cancer in infants and young children for the foreseeable future, it would seem advantageous for appropriately planned population pharmacokinetic studies to be carried out in this patient population.

Blood sample volumes in child health research: review of safe limits

OBJECTIVE

To determine paediatric blood sample volume limits that are consistent with physiological "minimal risk."

METHODS

A literature review was performed to search for evidence concerning the adverse effects of blood sampling in children and for guidelines on sampling volume in paediatric research. The search included Medline, EMBASE, other web-based and non-web-based sources and the bibliographies of the sources identified. Experts were also consulted.

FINDINGS

Five studies and nine guidelines were identified. Existing guidelines specify paediatric blood sample volume limits ranging from 1% to 5% of total blood volume (TBV) over 24 hours and up to 10% of TBV over 8 weeks. The evidence available is limited and includes findings from non-randomized studies showing a minimal risk with one-off sampling of up to 5% of TBV.

CONCLUSION

The evidence available is consistent with the conclusion that all identified guidelines are within the limits of "minimal risk." However, more and better evidence is required to draw firmer conclusions. Researchers and institutional review boards need to take into account the total sampling volume needed for both clinical care and research rather than for each alone. The child's general state of health should be considered and extra caution should be observed particularly with children whose illness can deplete blood volume or haemoglobin or hinder their replenishment. Local policies must also address the appropriateness and local acceptability of collection procedures and of the blood volumes drawn.

Pharmacokinetics of daunorubicin and daunorubicinol in infants with leukemia treated in the interfant 99 protocol

BACKGROUND

There is an extreme paucity of pharmacokinetic data for anticancer agents in infants. Therefore, we aimed at characterizing the pharmacokinetics for daunorubicin in infants and examined their relationship to age, body weight, and body surface area.

PROCEDURE

Leukemia patients treated according to the Interfant 99 protocol received 30 mg/m(2) daunorubicin, with dose reduction to 3/4 for patients 6-12 months old and 2/3 for patients <6 months, respectively. Plasma samples from 21 patients (aged 0.05-1.88 years) were collected and analyzed for daunorubicin and daunorubicinol. Samples from 12 children (age 1.6-18.8 years), who received daunorubicin in an earlier investigation, were used for pharmacokinetic model building using the software NONMEM.

RESULTS

Plasma concentration time profiles could be described using a two compartment model. Daunorubicin clearance was 43.9 L hr(-1) m(-2) +/- 65% and central volume of distribution 16.4 L m(-2) +/- 46%, whereas apparent clearance of daunorubicinol was 19.1 L hr(-1) m(-2) +/- 32% and apparent volume of distribution 228 L m(-2) +/- 80% (mean +/- interindividual variability). No age-dependency in any of the BSA-normalized pharmacokinetic parameters was observed. Consequently, due to the empirical dose reduction in infants the overall exposure to daunorubicinol in infants was smaller than would be expected from older children. Patients aged <6 months experienced more infections in the induction phase than the group aged 6-12 months at diagnosis. Other toxicities were similar in both groups.

CONCLUSION

We observed no indication of an age-dependency in the pharmacokinetics of daunorubicin. Pediatr Blood Cancer 2010;54:355-360.

Therapeutic drug monitoring of methotrexate on the pediatric oncology ward: can blood sampling from central venous accesses substitute for capillary finger punctures?

Intravenous methotrexate therapy with subsequent calcium folinate rescue is widely used for treatment of various neoplastic diseases, both in adults and in children. The optimization of the methotrexate dose and/or the calcium folinate rescue is based on pharmacokinetic data calculated from plasma concentrations collected after cessation of the methotrexate infusion. The aim of the present study was to evaluate the possibility of substituting capillary blood samples with blood samples drawn from central venous catheters (PORT-A-CATH) for therapeutic drug monitoring of methotrexate on the pediatric oncology ward. Nine cancer patients (4 females and 5 males; median age: 15 years; range: 5-20 years) were included. The quantitative analysis of methotrexate was carried out by fluorescence polarization immunoassay (FPIA). The concentrations of methotrexate in venous and capillary samples were closely correlated (rs = 0.98; P < 0.0001; n = 71). The venous/capillary plasma concentration ratio was 1.00 [median value; interquartile range (IQR): 0.882-1.094]; for 85% of the data points the ratio was 0.8 to 1.2, independent of drug concentration. The observed plasma concentration differences in blood samples drawn from central venous accesses and obtained from capillary blood samples in this study could have altered the calcium folinate rescue at 1 treatment occasion only. Plotting all measured methotrexate concentration time data for the individual patients during the elimination phase, on a chart including a normal elimination curve, is mandatory to enable proper handling of the subsequent rescue after high-dose methotrexate therapy. Blood sampling from the central venous access can be used only under certain circumstances for therapeutic drug monitoring of methotrexate. Carefully evaluated standardized instructions regarding rinsing, flushing, and discarding waste volumes, as well as precautions to minimize the required blood volume, are needed.

A systematic review of limited sampling strategies for platinum agents used in cancer chemotherapy

Despite evidence in the literature suggesting that a strong correlation exists between the pharmacokinetic parameters and pharmacodynamic effect of anticancer agents, many of these agents are still dosed by body surface area. Therapeutic drug monitoring with the aim of pharmacokinetic-guided dosing would not only maintain target concentrations associated with efficacy but may potentially minimise the likelihood of dose-related systemic toxicities. The pharmacokinetic parameter that displays the best correlation with the pharmacodynamics of anticancer drugs is the area under the plasma concentration-time curve (AUC). However, accurate determination of the AUC requires numerous blood samples over an extended interval, which is not feasible in clinical practice. Therefore, limited sampling strategies (LSSs) have been proposed as a means to accurately and precisely estimate pharmacokinetic parameters with a minimal number of blood samples. LSSs have been developed for many drugs, particularly ciclosporin and other immunosuppressants, as well as for certain anticancer drugs. This systematic review evaluates LSSs developed for the platinum compounds and categorises 18 pertinent citations according to criteria adapted from the US Preventive Services Task Force. Thirteen citations (four level I, six level II-1, three level II-2) pertained to LSSs for carboplatin, four citations (one level II-1, one level II-2, two level III) to cisplatin LSSs, and one citation (level II-2) to nedaplatin. Based on the current evidence, it appears that LSSs may be useful for pharmacokinetic-guided dosage adjustments of carboplatin in both adults and children with cancer. Although some validation studies suggest that LSSs can be extended to different cancer populations or different chemotherapy regimens, other studies dispute this finding. Although the use of LSSs to predict the pharmacokinetic parameters of cisplatin and nedaplatin appear promising, the quality of evidence from published studies does not support routine implementation at this time.LSSs represent one approach in which clinicians can make specific dosage adjustments for individual patients to optimise outcomes. However, the limitations of these strategies must also be taken into consideration. There is also a need for prospective studies to demonstrate that application of LSSs for platinum agents ultimately improves patient response and decreases systemic toxicities.

A study to determine the minimum volume of blood necessary to be discarded from a central venous catheter before a valid sample is obtained in children with cancer

BACKGROUND

The objective of this study was to determine the minimum volume of blood that should be discarded from a range of different types of central venous catheter (CVC), such that the subsequent blood sample was not diluted or contaminated by the residual intra-luminal fluid.

PROCEDURE

Seventy children aged 1-19 years with central venous access inserted as part of their standard clinical treatment were recruited to this prospective study. Statistical comparison of the extent of variation in biochemical and haematological parameters observed between two blood samples taken following routine 5 ml discard blood volumes, as compared to the extent of variation between samples drawn following a 5 ml discard volume and <5 ml volumes, was carried out.

RESULTS

Data indicate that the measurement error in a clinical sample obtained following a 3 ml discard volume is no different to the measurement error obtained when using a standard 5 ml discard volume. Comparable results were obtained from patients with various different types of CVC or portacath access.

CONCLUSIONS

The withdrawal of a 3 ml discard volume is sufficient to ensure that the subsequent blood sample is not diluted or contaminated by residual intra-luminal fluid. This may have a significant clinical impact in paediatric oncology, where patients frequently require blood transfusions due to the haematological toxicities associated with chemotherapy. It is hoped that these results will impact on hospital policies concerning specified discard volumes taken from CVCs prior to the withdrawal of blood samples for research purposes and routine clinical analysis.