Meta-analysis of tumor- and T cell-intrinsic mechanisms of sensitization to checkpoint inhibition.

Checkpoint inhibitors (CPIs) augment adaptive immunity. Systematic pan-tumor analyses may reveal the relative importance of tumor-cell-intrinsic and microenvironmental features underpinning CPI sensitization. Here, we collated whole-exome and transcriptomic data for >1,000 CPI-treated patients across seven tumor types, utilizing standardized bioinformatics workflows and clinical outcome criteria to validate multivariable predictors of CPI sensitization. Clonal tumor mutation burden (TMB) was the strongest predictor of CPI response, followed by total TMB and CXCL9 expression. Subclonal TMB, somatic copy alteration burden, and histocompatibility leukocyte antigen (HLA) evolutionary divergence failed to attain pan-cancer significance. Dinucleotide variants were identified as a source of immunogenic epitopes associated with radical amino acid substitutions and enhanced peptide hydrophobicity/immunogenicity. Copy-number analysis revealed two additional determinants of CPI outcome supported by prior functional evidence: 9q34 (TRAF2) loss associated with response and CCND1 amplification associated with resistance. Finally, single-cell RNA sequencing (RNA-seq) of clonal neoantigen-reactive CD8 tumor-infiltrating lymphocytes (TILs), combined with bulk RNA-seq analysis of CPI-responding tumors, identified CCR5 and CXCL13 as T-cell-intrinsic markers of CPI sensitivity.

Allele-Specific HLA Loss and Immune Escape in Lung Cancer Evolution.

Immune evasion is a hallmark of cancer. Losing the ability to present neoantigens through human leukocyte antigen (HLA) loss may facilitate immune evasion. However, the polymorphic nature of the locus has precluded accurate HLA copy-number analysis. Here, we present loss of heterozygosity in human leukocyte antigen (LOHHLA), a computational tool to determine HLA allele-specific copy number from sequencing data. Using LOHHLA, we find that HLA LOH occurs in 40% of non-small-cell lung cancers (NSCLCs) and is associated with a high subclonal neoantigen burden, APOBEC-mediated mutagenesis, upregulation of cytolytic activity, and PD-L1 positivity. The focal nature of HLA LOH alterations, their subclonal frequencies, enrichment in metastatic sites, and occurrence as parallel events suggests that HLA LOH is an immune escape mechanism that is subject to strong microenvironmental selection pressures later in tumor evolution. Characterizing HLA LOH with LOHHLA refines neoantigen prediction and may have implications for our understanding of resistance mechanisms and immunotherapeutic approaches targeting neoantigens. VIDEO ABSTRACT.

Genomic-transcriptomic evolution in lung cancer and metastasis.

Intratumour heterogeneity (ITH) fuels lung cancer evolution, which leads to immune evasion and resistance to therapy1. Here, using paired whole-exome and RNA sequencing data, we investigate intratumour transcriptomic diversity in 354 non-small cell lung cancer tumours from 347 out of the first 421 patients prospectively recruited into the TRACERx study2,3. Analyses of 947 tumour regions, representing both primary and metastatic disease, alongside 96 tumour-adjacent normal tissue samples implicate the transcriptome as a major source of phenotypic variation. Gene expression levels and ITH relate to patterns of positive and negative selection during tumour evolution. We observe frequent copy number-independent allele-specific expression that is linked to epigenomic dysfunction. Allele-specific expression can also result in genomic-transcriptomic parallel evolution, which converges on cancer gene disruption. We extract signatures of RNA single-base substitutions and link their aetiology to the activity of the RNA-editing enzymes ADAR and APOBEC3A, thereby revealing otherwise undetected ongoing APOBEC activity in tumours. Characterizing the transcriptomes of primary-metastatic tumour pairs, we combine multiple machine-learning approaches that leverage genomic and transcriptomic variables to link metastasis-seeding potential to the evolutionary context of mutations and increased proliferation within primary tumour regions. These results highlight the interplay between the genome and transcriptome in influencing ITH, lung cancer evolution and metastasis.

The evolution of lung cancer and impact of subclonal selection in TRACERx.

Lung cancer is the leading cause of cancer-associated mortality worldwide1. Here we analysed 1,644 tumour regions sampled at surgery or during follow-up from the first 421 patients with non-small cell lung cancer prospectively enrolled into the TRACERx study. This project aims to decipher lung cancer evolution and address the primary study endpoint: determining the relationship between intratumour heterogeneity and clinical outcome. In lung adenocarcinoma, mutations in 22 out of 40 common cancer genes were under significant subclonal selection, including classical tumour initiators such as TP53 and KRAS. We defined evolutionary dependencies between drivers, mutational processes and whole genome doubling (WGD) events. Despite patients having a history of smoking, 8% of lung adenocarcinomas lacked evidence of tobacco-induced mutagenesis. These tumours also had similar detection rates for EGFR mutations and for RET, ROS1, ALK and MET oncogenic isoforms compared with tumours in never-smokers, which suggests that they have a similar aetiology and pathogenesis. Large subclonal expansions were associated with positive subclonal selection. Patients with tumours harbouring recent subclonal expansions, on the terminus of a phylogenetic branch, had significantly shorter disease-free survival. Subclonal WGD was detected in 19% of tumours, and 10% of tumours harboured multiple subclonal WGDs in parallel. Subclonal, but not truncal, WGD was associated with shorter disease-free survival. Copy number heterogeneity was associated with extrathoracic relapse within 1 year after surgery. These data demonstrate the importance of clonal expansion, WGD and copy number instability in determining the timing and patterns of relapse in non-small cell lung cancer and provide a comprehensive clinical cancer evolutionary data resource.

Using DNA sequencing data to quantify T cell fraction and therapy response.

The immune microenvironment influences tumour evolution and can be both prognostic and predict response to immunotherapy1,2. However, measurements of tumour infiltrating lymphocytes (TILs) are limited by a shortage of appropriate data. Whole-exome sequencing (WES) of DNA is frequently performed to calculate tumour mutational burden and identify actionable mutations. Here we develop T cell exome TREC tool (T cell ExTRECT), a method for estimation of T cell fraction from WES samples using a signal from T cell receptor excision circle (TREC) loss during V(D)J recombination of the T cell receptor-α gene (TCRA (also known as TRA)). TCRA T cell fraction correlates with orthogonal TIL estimates and is agnostic to sample type. Blood TCRA T cell fraction is higher in females than in males and correlates with both tumour immune infiltrate and presence of bacterial sequencing reads. Tumour TCRA T cell fraction is prognostic in lung adenocarcinoma. Using a meta-analysis of tumours treated with immunotherapy, we show that tumour TCRA T cell fraction predicts immunotherapy response, providing value beyond measuring tumour mutational burden. Applying T cell ExTRECT to a multi-sample pan-cancer cohort reveals a high diversity of the degree of immune infiltration within tumours. Subclonal loss of 12q24.31-32, encompassing SPPL3, is associated with reduced TCRA T cell fraction. T cell ExTRECT provides a cost-effective technique to characterize immune infiltrate alongside somatic changes.

Pervasive chromosomal instability and karyotype order in tumour evolution.

Chromosomal instability in cancer consists of dynamic changes to the number and structure of chromosomes1,2. The resulting diversity in somatic copy number alterations (SCNAs) may provide the variation necessary for tumour evolution1,3,4. Here we use multi-sample phasing and SCNA analysis of 1,421 samples from 394 tumours across 22 tumour types to show that continuous chromosomal instability results in pervasive SCNA heterogeneity. Parallel evolutionary events, which cause disruption in the same genes (such as BCL9, MCL1, ARNT (also known as HIF1B), TERT and MYC) within separate subclones, were present in 37% of tumours. Most recurrent losses probably occurred before whole-genome doubling, that was found as a clonal event in 49% of tumours. However, loss of heterozygosity at the human leukocyte antigen (HLA) locus and loss of chromosome 8p to a single haploid copy recurred at substantial subclonal frequencies, even in tumours with whole-genome doubling, indicating ongoing karyotype remodelling. Focal amplifications that affected chromosomes 1q21 (which encompasses BCL9, MCL1 and ARNT), 5p15.33 (TERT), 11q13.3 (CCND1), 19q12 (CCNE1) and 8q24.1 (MYC) were frequently subclonal yet appeared to be clonal within single samples. Analysis of an independent series of 1,024 metastatic samples revealed that 13 focal SCNAs were enriched in metastatic samples, including gains in chromosome 8q24.1 (encompassing MYC) in clear cell renal cell carcinoma and chromosome 11q13.3 (encompassing CCND1) in HER2+ breast cancer. Chromosomal instability may enable the continuous selection of SCNAs, which are established as ordered events that often occur in parallel, throughout tumour evolution.

Neoantigen-directed immune escape in lung cancer evolution.

The interplay between an evolving cancer and a dynamic immune microenvironment remains unclear. Here we analyse 258 regions from 88 early-stage, untreated non-small-cell lung cancers using RNA sequencing and histopathology-assessed tumour-infiltrating lymphocyte estimates. Immune infiltration varied both between and within tumours, with different mechanisms of neoantigen presentation dysfunction enriched in distinct immune microenvironments. Sparsely infiltrated tumours exhibited a waning of neoantigen editing during tumour evolution, indicative of historical immune editing, or copy-number loss of previously clonal neoantigens. Immune-infiltrated tumour regions exhibited ongoing immunoediting, with either loss of heterozygosity in human leukocyte antigens or depletion of expressed neoantigens. We identified promoter hypermethylation of genes that contain neoantigenic mutations as an epigenetic mechanism of immunoediting. Our results suggest that the immune microenvironment exerts a strong selection pressure in early-stage, untreated non-small-cell lung cancers that produces multiple routes to immune evasion, which are clinically relevant and forecast poor disease-free survival.

Corrigendum: Phylogenetic ctDNA analysis depicts early-stage lung cancer evolution.

This corrects the article DOI: 10.1038/nature22364.

Discrepancy in Reporting of Perioperative Complications: A Retrospective Observational Study.

OBJECTIVE: To assess the discrepancy between perioperative complications, prospectively recorded during a cohort study versus retrospectively from health records. BACKGROUND: Perioperative adverse events are relevant for patient outcome, but incomplete reporting is common. METHODS: Two physicians independently recorded all intraoperative adverse events according to ClassIntra and all postoperative complications according to the Clavien-Dindo classification based on all available health records. These retrospective assessments were compared with the number and severity of those prospectively assessed in the same patients during their inclusion in 1 center of a prospective multicenter cohort study. RESULTS: Interrater agreement between both physicians for retrospective recording was high [intraclass correlation coefficient: 0.89 (95% CI, 0.86, 0.91) for intraoperative and 0.88 (95% CI, 0.85, 0.90) for postoperative complications]. In 320 patients, the incidence rate was higher retrospectively than prospectively for any intraoperative complication (incidence rate ratio: 1.79; 95% CI, 1.50, 2.13) and for any postoperative complication (incidence rate ratio: 2.21; 95% CI, 1.90, 2.56). In 71 patients, the severity of the most severe intraoperative complication was higher in the retrospective than in the prospective data collection, whereas in 69 the grading was lower. In 106 patients, the severity of the most severe postoperative complication was higher in the retrospective than in the prospective data collection, whereas in 19 the grading was lower. CONCLUSIONS: There is a noticeable discrepancy in the number and severity of reported perioperative complications between these 2 data collection methods. On the basis of the double-blinded assessment of 2 independent raters, our study renders prospective underreporting more likely than retrospective overreporting.

Phylogenetic ctDNA analysis depicts early-stage lung cancer evolution.

The early detection of relapse following primary surgery for non-small-cell lung cancer and the characterization of emerging subclones, which seed metastatic sites, might offer new therapeutic approaches for limiting tumour recurrence. The ability to track the evolutionary dynamics of early-stage lung cancer non-invasively in circulating tumour DNA (ctDNA) has not yet been demonstrated. Here we use a tumour-specific phylogenetic approach to profile the ctDNA of the first 100 TRACERx (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy (Rx)) study participants, including one patient who was also recruited to the PEACE (Posthumous Evaluation of Advanced Cancer Environment) post-mortem study. We identify independent predictors of ctDNA release and analyse the tumour-volume detection limit. Through blinded profiling of postoperative plasma, we observe evidence of adjuvant chemotherapy resistance and identify patients who are very likely to experience recurrence of their lung cancer. Finally, we show that phylogenetic ctDNA profiling tracks the subclonal nature of lung cancer relapse and metastasis, providing a new approach for ctDNA-driven therapeutic studies.

Understanding the impact of immune-mediated selection on lung cancer evolution.

Understanding how a tumour evolves and avoids immune recognition is paramount to improving cancer immunotherapy and patient outcome. Here we examine our recent integration of multi-region genomic, transcriptomic, epigenomic, pathology, and clinical data, highlight the need for a systematic examination of immune escape mechanisms, and discuss implications for immunotherapy approaches.

[Prospective Cohort Study of In-Hospital Patients Undergoing Ophthalmic Surgery for the Validation of ClassIntra: Classification of Intraoperative Adverse Events]. / Prospektive Kohortenstudie bei stationären augenchirurgischen Patienten für die Validierung der ClassIntra-Klassifikation für unerwünschte intraoperative Ereignisse.

BACKGROUND: To the best of our knowledge, there is no validated classification to assess intraoperative adverse events (iAEs) in ophthalmic surgery. ClassIntra is a newly developed classification for surgery- and anaesthesia-related iAEs that has been recently validated in various surgical disciplines, but not in ophthalmic surgery. We aim to assess the validity and practicability of ClassIntra in patients undergoing ophthalmic surgery. METHODS: A consecutive sample of in-hospital patients undergoing any type of ophthalmic surgery was included in this single-centre prospective cohort study. iAEs were classified using ClassIntra, consisting of 5 severity grades according to the symptoms of the patient and the required treatment. All patients were followed for two weeks to record all postoperative adverse events according to Clavien-Dindo. The primary endpoint was the risk-adjusted association between the most severe iAE and the weighted sum of all postoperative adverse events within the two-week follow-up using the Comprehensive Complication Index (CCI). In addition, ophthalmologists and anaesthesiologists were asked to complete an online survey assessing the severity of iAEs for 10 fictitious clinical case scenarios. Reliability was assessed by comparing the clinicians' ratings to the prespecified benchmark rating of the study team. RESULTS: In this study, 100 in-hospital patients with an average age of 64 years (SD 15) were included. The majority of all patients were ASA II (n = 53, 53%) or III (n = 42, 42%). Thirty-two iAEs were recorded in 22 patients (17 grade I, 12 grade II, 3 grade III). Ninety-four postoperative adverse events occurred in 50 patients (44 grade I, 36 grade II, 14 grade IIIa). We found a mean difference in CCI of 2,1 (95% confidence interval [CI] - 2,5 to 6,8) per one unit increase in severity grades of ClassIntra. Fifty ophthalmologists and anaesthesiologists completed the online survey (response rate 54%). The intraclass correlation coefficient was 0,79 (95% CI 0,64 to 0,94). CONCLUSIONS: The application of ClassIntra during daily routine in ophthalmic surgery showed the usefulness and practicability of this classification for the standardised assessment of intraoperative adverse events. Although construct validity could not be demonstrated, the good reliability in the survey's rating underlines the criterion validity of this newly developed classification in ophthalmic surgery.

Tracking the Evolution of Non-Small-Cell Lung Cancer.

BACKGROUND: Among patients with non-small-cell lung cancer (NSCLC), data on intratumor heterogeneity and cancer genome evolution have been limited to small retrospective cohorts. We wanted to prospectively investigate intratumor heterogeneity in relation to clinical outcome and to determine the clonal nature of driver events and evolutionary processes in early-stage NSCLC. METHODS: In this prospective cohort study, we performed multiregion whole-exome sequencing on 100 early-stage NSCLC tumors that had been resected before systemic therapy. We sequenced and analyzed 327 tumor regions to define evolutionary histories, obtain a census of clonal and subclonal events, and assess the relationship between intratumor heterogeneity and recurrence-free survival. RESULTS: We observed widespread intratumor heterogeneity for both somatic copy-number alterations and mutations. Driver mutations in EGFR, MET, BRAF, and TP53 were almost always clonal. However, heterogeneous driver alterations that occurred later in evolution were found in more than 75% of the tumors and were common in PIK3CA and NF1 and in genes that are involved in chromatin modification and DNA damage response and repair. Genome doubling and ongoing dynamic chromosomal instability were associated with intratumor heterogeneity and resulted in parallel evolution of driver somatic copy-number alterations, including amplifications in CDK4, FOXA1, and BCL11A. Elevated copy-number heterogeneity was associated with an increased risk of recurrence or death (hazard ratio, 4.9; P=4.4×10-4), which remained significant in multivariate analysis. CONCLUSIONS: Intratumor heterogeneity mediated through chromosome instability was associated with an increased risk of recurrence or death, a finding that supports the potential value of chromosome instability as a prognostic predictor. (Funded by Cancer Research UK and others; TRACERx ClinicalTrials.gov number, NCT01888601 .).

Life-saving myocarditis? A case in a young adult leading to discovery of an anomalous origin of the right coronary artery.

Myocarditis and coronary artery anomalies are both potentially life-threatening aetiologies of cardiac chest pain in children. We present a case of a young man presenting with non-exertional chest pain and subsequently found to have an anomalous origin of the right coronary artery from the left coronary sinus with an interarterial course in addition to a diagnosis of myocarditis. The patient subsequently was able to undergo surgical correction of his anomalous coronary to mitigate the risk of sudden cardiac death.

High-resolution standardization reduces delay due to workflow disruptions in laparoscopic cholecystectomy.

BACKGROUND: Optimal resource utilization in high-cost environments like operating theatres is fundamental in today's cost constrained health care systems. Interruptions of the surgical workflow, i.e. microcomplications (MC), lead to prolonged procedure times and higher costs and can be indicative of surgical mistakes. Reducing MC can improve operating room efficiency and prevent intraoperative complications. We, therefore, aimed to evaluate the impact of a high-resolution standardized laparoscopic cholecystectomy protocol (HRSL) on operative time and intraoperative interruptions in a teaching hospital. METHODS: HRSL consisted of a detailed stepwise protocol for the procedure, supported by a teaching video, both to be reviewed as mandatory preparation by each team member before surgery. Audio-video records of laparoscopic cholecystectomies were reviewed regarding type, frequency and duration of MC before and after implementation of HRSL. RESULTS: Thirty-nine (20 control and 19 HRSL) audio-video records of laparoscopic cholecystectomies with a total duration of 51.36 h (28.92 pre 22.44 post) were reviewed. The majority of operations (86%) were performed by teams who had completed less than 10 procedures together previously. Communication-related interruptions and instrument changes accounted for the majority of MC. Median frequency and duration of MC were 95 events/h and 15.6 min/h, respectively, of surgery pre-intervention. With HRSL this was reduced to 76 events/h and 10.6 min/h of operating. In multivariable analysis, HRSL was an independent predictor for shorter delay and lower frequency of MC [percentage decrease 27% (95% CI 18-35%), resp. 30% (95% CI 19-40%)]. Procedure-related risk factors for the longer delay due to MC in multivariable analysis were less experience of the surgeon and intraoperative adhesiolysis. CONCLUSIONS: HRSL is effective in reducing delays due to MC in a teaching institution with limited team experience. These findings should be tested in larger potentially cluster-randomized controlled trials. The trial has been registered with clinicaltrials.gov: NCT03329859.

Minimally invasive anterior muscle-sparing versus a transgluteal approach for hemiarthroplasty in femoral neck fractures-a prospective randomised controlled trial including 190 elderly patients.

BACKGROUND: The relevance of femoral neck fractures (FNFs) increases with the ageing of numerous societies, injury-related decline is observed in many patients. Treatment strategies have evolved towards primary joint replacement, but the impact of different approaches remains a matter of debate. The aim of this trial was to evaluate the benefit of an anterior minimally-invasive (AMIS) compared to a lateral Hardinge (LAT) approach for hemiarthroplasty in these oftentimes frail patients. METHODS: Four hundred thirty-nine patients were screened during the 44-months trial, aiming at the evaluation of 150 patients > 60 yrs. of age. Eligible patients were randomised using an online-tool with completely random assignment. As primary endpoint, early mobility, a predictor for long-term outcomes, was evaluated at 3 weeks via the "Timed up and go" test (TUG). Secondary endpoints included the Functional Independence Measure (FIM), pain, complications, one-year mobility and mortality. RESULTS: A total of 190 patients were randomised; both groups were comparable at baseline, with a predominance for frailty-associated factors in the AMIS-group. At 3 weeks, 146 patients were assessed for the primary outcome. There was a reduction in the median duration of TUG performance of 21.5% (CI [- 41.2,4.7], p = 0.104) in the AMIS-arm (i.e., improved mobility). This reduction was more pronounced in patients with signs of frailty or cognitive impairment. FIM scores increased on average by 6.7 points (CI [0.5-12.8], p = 0.037), pain measured on a 10-point visual analogue scale decreased on average by 0.7 points (CI: [- 1.4,0.0], p = 0.064). The requirement for blood transfusion was lower in the AMIS- group, the rate of complications comparable, with a higher rate of soft tissue complications in the LAT-group. The mortality was higher in the AMIS-group. CONCLUSION: These results, similar to previous reports, support the concept that in elderly patients at risk of frailty, the AMIS approach for hemiarthroplasty can be beneficial, since early mobilisation and pain reduction potentially reduce deconditioning, morbidity and loss of independence. The results are, however, influenced by a plethora of factors. Only improvements in every aspect of the therapeutic chain can lead to optimisation of treatment and improve outcomes in this growing patient population. TRIAL REGISTRATION: www.clinicaltrials.gov : NCT01408693 (registered August 3rd 2011).

Insertion-and-deletion-derived tumour-specific neoantigens and the immunogenic phenotype: a pan-cancer analysis.

BACKGROUND: The focus of tumour-specific antigen analyses has been on single nucleotide variants (SNVs), with the contribution of small insertions and deletions (indels) less well characterised. We investigated whether the frameshift nature of indel mutations, which create novel open reading frames and a large quantity of mutagenic peptides highly distinct from self, might contribute to the immunogenic phenotype. METHODS: We analysed whole-exome sequencing data from 5777 solid tumours, spanning 19 cancer types from The Cancer Genome Atlas. We compared the proportion and number of indels across the cohort, with a subset of results replicated in two independent datasets. We assessed in-silico tumour-specific neoantigen predictions by mutation type with pan-cancer analysis, together with RNAseq profiling in renal clear cell carcinoma cases (n=392), to compare immune gene expression across patient subgroups. Associations between indel burden and treatment response were assessed across four checkpoint inhibitor datasets. FINDINGS: We observed renal cell carcinomas to have the highest proportion (0·12) and number of indel mutations across the pan-cancer cohort (p<2·2 × 10-16), more than double the median proportion of indel mutations in all other cancer types examined. Analysis of tumour-specific neoantigens showed that enrichment of indel mutations for high-affinity binders was three times that of non-synonymous SNV mutations. Furthermore, neoantigens derived from indel mutations were nine times enriched for mutant specific binding, as compared with non-synonymous SNV derived neoantigens. Immune gene expression analysis in the renal clear cell carcinoma cohort showed that the presence of mutant-specific neoantigens was associated with upregulation of antigen presentation genes, which correlated (r=0·78) with T-cell activation as measured by CD8-positive expression. Finally, analysis of checkpoint inhibitor response data revealed frameshift indel count to be significantly associated with checkpoint inhibitor response across three separate melanoma cohorts (p=4·7 × 10-4). INTERPRETATION: Renal cell carcinomas have the highest pan-cancer proportion and number of indel mutations. Evidence suggests indels are a highly immunogenic mutational class, which can trigger an increased abundance of neoantigens and greater mutant-binding specificity. FUNDING: Cancer Research UK, UK National Institute for Health Research (NIHR) at the Royal Marsden Hospital National Health Service Foundation Trust, Institute of Cancer Research and University College London Hospitals Biomedical Research Centres, the UK Medical Research Council, the Rosetrees Trust, Novo Nordisk Foundation, the Prostate Cancer Foundation, the Breast Cancer Research Foundation, the European Research Council.

Premature Discontinuation of Pediatric Randomized Controlled Trials: A Retrospective Cohort Study.

OBJECTIVES: To determine the proportion of pediatric randomized controlled trials (RCTs) that are prematurely discontinued, examine the reasons for discontinuation, and compare the risk for recruitment failure in pediatric and adult RCTs. STUDY DESIGN: A retrospective cohort study of RCTs approved by 1 of 6 Research Ethics Committees (RECs) in Switzerland, Germany, and Canada between 2000 and 2003. We recorded trial characteristics, trial discontinuation, and reasons for discontinuation from protocols, corresponding publications, REC files, and a survey of trialists. RESULTS: We included 894 RCTs, of which 86 enrolled children and 808 enrolled adults. Forty percent of the pediatric RCTs and 29% of the adult RCTs were discontinued. Slow recruitment accounted for 56% of pediatric RCT discontinuations and 43% of adult RCT discontinuations. Multivariable logistic regression analyses suggested that pediatric RCT was not an independent risk factor for recruitment failure after adjustment for other potential risk factors (aOR, 1.22; 95% CI, 0.57-2.63). Independent risk factors were acute care setting (aOR, 4.00; 95% CI, 1.72-9.31), nonindustry sponsorship (aOR, 4.45; 95% CI, 2.59-7.65), and smaller planned sample size (aOR, 1.05; 95% CI 1.01-1.09, in decrements of 100 participants). CONCLUSION: Forty percent of pediatric RCTs were discontinued prematurely, owing predominately to slow recruitment. Enrollment of children was not an independent risk factor for recruitment failure.

Colon Perfusion Patterns During Colorectal Resection Using Visible Light Spectroscopy.

BACKGROUND: The impact of blood supply to the anastomosis on development of anastomotic leakage is still a matter of debate. Considering that bowel perfusion may be affected by manipulation during surgery, perfusion assessment of the anastomosis alone may be of limited value. We propose perfusion assessment at different time points during surgery to explore the dynamics of bowel perfusion during colorectal resection and its impact on outcome. METHODS: In this prospective cohort study, patients undergoing elective colorectal resection were eligible. Colon perfusion was evaluated using visible light spectroscopy. Main outcome was the difference in colon perfusion, quantified by measuring tissue oxygen saturation (StO2) in the colonic serosa, before and after anastomosis during surgery. RESULTS: We included 58 patients between July 2013 and November 2015. Colon perfusion increased by an average of 5.9% StO2 during surgery (95% confidence interval 3.1, 8.8; P < 0.001). The number of patients with abnormal perfusion (defined as StO2 < 65%) decreased from 50% at the beginning to 24% by the end of surgery. Six patients (10%) developed anastomotic leaks (AL), of which five patients had abnormal perfusion at the beginning of surgery, whereas four patients had normal StO2 at the anastomosis. CONCLUSION: Colon perfusion significantly increased during colorectal surgery. Considering that one quarter of patients had suboptimal anastomotic perfusion without developing AL, impaired blood flow at the anastomosis alone does not seem to be critical. Further investigations including more patients are necessary to evaluate the impact of perioperative parameters on colon perfusion, anastomotic healing and surgical outcome.