A practical guide to the appropriate analysis of eGFR data over time: A simulation study.

In several therapeutic areas, including chronic kidney disease (CKD) and immunoglobulin A nephropathy (IgAN), there is a growing interest in how best to analyze estimated glomerular filtration rate (eGFR) data over time in randomized clinical trials including how to best accommodate situations where the rate of change is not anticipated to be linear over time, often due to possible short term hemodynamic effects of certain classes of interventions. In such situations, concerns have been expressed by regulatory authorities that the common application of single slope analysis models may induce Type I error inflation. This article aims to offer practical advice and guidance, including SAS codes, on the statistical methodology to be employed in an eGFR rate of change analysis and offers guidance on trial design considerations for eGFR endpoints. A two-slope statistical model for eGFR data over time is proposed allowing for an analysis to simultaneously evaluate short term acute effects and long term chronic effects. A simulation study was conducted under a range of credible null and alternative hypotheses to evaluate the performance of the two-slope model in comparison to commonly used single slope random coefficients models as well as to non-slope based analyses of change from baseline or time normalized area under the curve (TAUC). Importantly, and contrary to preexisting concerns, these simulations demonstrate the absence of alpha inflation associated with the use of single or two-slope random coefficient models, even when such models are misspecified, and highlight that any concern regarding model misspecification relates to power and not to lack of Type I error control.

Conditional power and information fraction calculations at an interim analysis for random coefficient models.

Random coefficient (RC) models are commonly used in clinical trials to estimate the rate of change over time in longitudinal data. Trials utilizing a surrogate endpoint for accelerated approval with a confirmatory longitudinal endpoint to show clinical benefit is a strategy implemented across various therapeutic areas, including immunoglobulin A nephropathy. Understanding conditional power (CP) and information fraction calculations of RC models may help in the design of clinical trials as well as provide support for the confirmatory endpoint at the time of accelerated approval. This paper provides calculation methods, with practical examples, for determining CP at an interim analysis for a RC model with longitudinal data, such as estimated glomerular filtration rate (eGFR) assessments to measure rate of change in eGFR slope.

Theory of Mind and Social Informant Discrepancy in Autism.

When autistic youth are asked to assess their own social skills, they frequently rate themselves more favorably than their parents rate them. The magnitude of this informant discrepancy has been shown to relate to key clinical outcomes such as treatment response. It has been proposed that this discrepancy arises from difficulties with Theory of Mind. Participants were 167 youth 11 to 17 years old; 72% male, and their parents. Youth completed self-report measures of social skills and social cognitive tasks, while their parents completed questionnaires regarding social skills. A repeated-measures ANOVA indicated both non-autistic and autistic youth rated themselves more favorably than their parents rated them across all measures. Zero-order correlations revealed that raw differences between parent- and participant-report were negatively correlated with scores on parent-reported Theory of Mind measures. However, polynomial analysis did not indicate interaction effects between parent- and participant-report on any of the measures used. Polynomial regression revealed that increases in parent-reported social skill predicted larger increases in parent-report Theory of Mind at low levels of parent-reported social skill compared to high levels of parent-reported social skill. Participant-report social skills predicted performance on a behavioral Theory of Mind test in a curvilinear fashion, such that the relationship was positive at low levels of participant-reported social skills, but negative at high levels. This study replicates the finding that raw difference score analyses may result in illusory effects that are not supported when using more contemporary analysis methods, and that more complex and subtle relationships between social insight and perspective-taking exist within autistic youth.

Subsequent urinary stone events are predicted by the magnitude of urinary oxalate excretion in enteric hyperoxaluria.

Data directly demonstrating the relationship between urinary oxalate (UOx) excretion and stone events in those with enteric hyperoxaluria (EH) are limited. Therefore, we assessed the relationship between UOx excretion and risk of kidney stone events in a retrospective population-based EH cohort. In all, 297 patients from Olmsted County, Minnesota were identified with EH based upon having a 24-h UOx ≥40 mg/24 h preceded by a diagnosis or procedure associated with malabsorption. Diagnostic codes and urologic procedures consistent with kidney stones during follow-up after baseline UOx were considered a new stone event. Logistic regression and accelerated failure time modeling were performed as a function of UOx excretion to predict the probability of new stone event and the annual rate of stone events, respectively, with adjustment for urine calcium and citrate. Mean ± standard deviation age was 51.4 ± 11.4 years and 68% were female. Median (interquartile range) UOx was 55.4 (46.6-73.0) mg/24 h and 81 patients had one or more stone event during a median follow-up time of 4.9 (2.8-7.8) years. Higher UOx was associated with a higher probability of developing a stone event (P < 0.01) and predicted an increased annual risk of kidney stones (P = 0.001). Estimates derived from these analyses suggest that a 20% decrease in UOx is associated with 25% reduction in the annual odds of a future stone event. Thus, these data demonstrate an association between baseline UOx and stone events in EH patients and highlight the potential benefit of strategies to reduce UOx in this patient group. BACKGROUND: Data directly demonstrating the relationship between urinary oxalate (UOx) excretion and stone events in those with enteric hyperoxaluria (EH) are limited. METHODS: We assessed the relationship between UOx excretion and risk of kidney stone events in a retrospective population-based EH cohort. In all, 297 patients from Olmsted County, Minnesota were identified with EH based upon having a 24-h UOx ≥40 mg/24 h preceded by a diagnosis or procedure associated with malabsorption. Diagnostic codes and urologic procedures consistent with kidney stones during follow-up after baseline UOx were considered a new stone event. Logistic regression and accelerated failure time modeling were performed as a function of UOx excretion to predict the probability of new stone event and the annual rate of stone events, respectively, with adjustment for urine calcium and citrate. RESULTS: Mean ± SD age was 51.4 ± 11.4 years and 68% were female. Median (interquartile range) UOx was 55.4 (46.6-73.0) mg/24 h and 81 patients had ≥1 stone event during a median follow-up time of 4.9 (2.8-7.8) years. Higher UOx was associated with a higher probability of developing a stone event (P < 0.01) and predicted an increased annual risk of kidney stones (P = 0.001). Estimates derived from these analyses suggest that a 20% decrease in UOx is associated with 25% reduction in the annual odds of a future stone event. CONCLUSIONS: These data demonstrate an association between baseline UOx and stone events in EH patients and highlight the potential benefit of strategies to reduce UOx in this patient group.

Batch Selection via In Vitro/In Vivo Correlation in Pharmacokinetic Bioequivalence Testing.

Pharmacokinetic differences between manufacturing batches, well established for inhaled drug products, preclude control of patient risk in the customary two-way (single batch) pharmacokinetic bioequivalence crossover design if batches are randomly chosen. European regulators have recommended selecting a "typical" in vitro batch to represent each product in pharmacokinetic bioequivalence testing. We explored the feasibility of this approach to control patient risk (the "false equivalence", or Type I, error rate). The probability of achieving a Test/Reference 90% confidence interval within (0.80, 1.25) for a true (non-equivalent) value of 1.25 was simulated for a two-way crossover design using the median in vitro batch across a range of number of in vitro batches, in vitro/in vivo correlation (IVIVC) quality (correlation coefficient, r, of zero to one), and within-subject between-batch pharmacokinetic variability. Even under extremely optimistic conditions, e.g., r=0.95 and >100 batches per product screened in vitro, patient risk for typical between-batch variability levels remained at least threefold higher than the 5% regulatory expectation for the significance level (the false equivalence error rate) of the pharmacokinetic bioequivalence test. This elevated error rate in bioequivalence decision-making occurs because of incomplete confidence that the true product average has been identified, and, importantly, omission of this uncertainty from the bioequivalence confidence interval.

Performance of Multiple-Batch Approaches to Pharmacokinetic Bioequivalence Testing for Orally Inhaled Drug Products with Batch-to-Batch Variability.

Batch-to-batch pharmacokinetic (PK) variability of orally inhaled drug products has been documented and can render single-batch PK bioequivalence (BE) studies unreliable; results from one batch may not be consistent with a repeated study using a different batch, yet the goal of PK BE is to deliver a product comparison that is interpretable beyond the specific batches used in the study. We characterized four multiple-batch PK BE approaches to improve outcome reliability without increasing the number of clinical study participants. Three approaches include multiple batches directly in the PK BE study with batch identity either excluded from the statistical model ("Superbatch") or included as a fixed or random effect ("Fixed Batch Effect," "Random Batch Effect"). A fourth approach uses a bio-predictive in vitro test to screen candidate batches, bringing the median batch of each product into the PK BE study ("Targeted Batch"). Three of these approaches (Fixed Batch Effect, Superbatch, Targeted Batch) continue the single-batch PK BE convention in which uncertainty in the Test/Reference ratio estimate due to batch sampling is omitted from the Test/Reference confidence interval. All three of these approaches provided higher power to correctly identify true bioequivalence than the standard single-batch approach with no increase in clinical burden. False equivalence (type I) error was inflated above the expected 5% level, but multiple batches controlled type I error better than a single batch. The Random Batch Effect approach restored 5% type I error, but had low power for small (e.g., <8) batch sample sizes using standard [0.8000, 1.2500] bioequivalence limits.

Comparisons of global tests on intersection hypotheses and their application in matched parallel gatekeeping procedures.

A clinical trial often has primary and secondary endpoints and comparisons of high and low doses of a study drug to a control. Multiplicity is not only caused by the multiple comparisons of study drugs versus the control, but also from the hierarchical structure of the hypotheses. Closed test procedures were proposed as general methods to address multiplicity. Two commonly used tests for intersection hypotheses in closed test procedures are the Simes test and the average method. When the treatment effect of a less efficacious dose is not much smaller than the treatment effect of a more efficacious dose for a specific endpoint, the average method has better power than the Simes test for the comparison of two doses versus control. Accordingly, for inferences for primary and secondary endpoints, the matched parallel gatekeeping procedure based on the Simes test for testing intersection hypotheses is extended here to allow the average method for such testing. This procedure is further extended to clinical trials with more than two endpoints as well as to clinical trials with more than two active doses and a control.

Coping with missing data in phase III pivotal registration trials: Tolvaptan in subjects with kidney disease, a case study.

Missing data cause challenging issues, particularly in phase III registration trials, as highlighted by the European Medicines Agency (EMA) and the US National Research Council. We explore, as a case study, how the issues from missing data were tackled in a double-blind phase III trial in subjects with autosomal dominant polycystic kidney disease. A total of 1445 subjects were randomized in a 2:1 ratio to receive active treatment (tolvaptan), or placebo. The primary outcome, the rate of change in total kidney volume, favored tolvaptan (P < .0001). The key secondary efficacy endpoints of clinical progression of disease and rate of decline in kidney function also favored tolvaptan. However, as highlighted by Food and Drug Administration and EMA, the interpretation of results was hampered by a high number of unevenly distributed dropouts, particularly early dropouts. In this paper, we outline the analyses undertaken to address the issue of missing data thoroughly. "Tipping point analyses" were performed to explore how extreme and detrimental outcomes among subjects with missing data must be to overturn the positive treatment effect attained in those subjects who had complete data. Nonparametric rank-based analyses were also performed accounting for missing data. In conclusion, straightforward and transparent analyses directly taking into account missing data convincingly support the robustness of the preplanned analyses on the primary and secondary endpoints. Tolvaptan was confirmed to be effective in slowing total kidney volume growth, which is considered an efficacy endpoint by EMA, and in lessening the decline in renal function in patients with autosomal dominant polycystic kidney disease.

Randomised, open-label, phase II study of gemcitabine with and without IMM-101 for advanced pancreatic cancer.

BACKGROUND: Immune Modulation and Gemcitabine Evaluation-1, a randomised, open-label, phase II, first-line, proof of concept study (NCT01303172), explored safety and tolerability of IMM-101 (heat-killed Mycobacterium obuense; NCTC 13365) with gemcitabine (GEM) in advanced pancreatic ductal adenocarcinoma. METHODS: Patients were randomised (2 : 1) to IMM-101 (10 mg ml(-l) intradermally)+GEM (1000 mg m(-2) intravenously; n=75), or GEM alone (n=35). Safety was assessed on frequency and incidence of adverse events (AEs). Overall survival (OS), progression-free survival (PFS) and overall response rate (ORR) were collected. RESULTS: IMM-101 was well tolerated with a similar rate of AE and serious adverse event reporting in both groups after allowance for exposure. Median OS in the intent-to-treat population was 6.7 months for IMM-101+GEM v 5.6 months for GEM; while not significant, the hazard ratio (HR) numerically favoured IMM-101+GEM (HR, 0.68 (95% CI, 0.44-1.04, P=0.074). In a pre-defined metastatic subgroup (84%), OS was significantly improved from 4.4 to 7.0 months in favour of IMM-101+GEM (HR, 0.54, 95% CI 0.33-0.87, P=0.01). CONCLUSIONS: IMM-101 with GEM was as safe and well tolerated as GEM alone, and there was a suggestion of a beneficial effect on survival in patients with metastatic disease. This warrants further evaluation in an adequately powered confirmatory study.

Early Change in Urine Protein as a Surrogate End Point in Studies of IgA Nephropathy: An Individual-Patient Meta-analysis.

BACKGROUND: The role of change in proteinuria as a surrogate end point for randomized trials in immunoglobulin A nephropathy (IgAN) has previously not been thoroughly evaluated. STUDY DESIGN: Individual patient-level meta-analysis. SETTING & POPULATION: Individual-patient data for 830 patients from 11 randomized trials evaluating 4 intervention types (renin-angiotensin system [RAS] blockade, fish oil, immunosuppression, and steroids) examining associations between changes in urine protein and clinical end points at the individual and trial levels. SELECTION CRITERIA FOR STUDIES: Randomized controlled trials of IgAN with measurements of proteinuria at baseline and a median of 9 (range, 5-12) months follow-up, with at least 1 further year of follow-up for the clinical outcome. PREDICTOR: 9-month change in proteinuria. OUTCOME: Doubling of serum creatinine level, end-stage renal disease, or death. RESULTS: Early decline in proteinuria at 9 months was associated with lower risk for the clinical outcome (HR per 50% reduction in proteinuria, 0.40; 95% CI, 0.32-0.48) and was consistent across studies. Proportions of treatment effect on the clinical outcome explained by early decline in proteinuria were estimated at 11% (95% CI, -19% to 41%) for RAS blockade and 29% (95% CI, 6% to 53%) for steroid therapy. The direction of the pooled treatment effect on early change in proteinuria was in accord with the direction of the treatment effect on the clinical outcome for steroids and RAS blockade. Trial-level analyses estimated that the slope for the regression line for the association of treatment effects on the clinical end points and for the treatment effect on proteinuria was 2.15 (95% Bayesian credible interval, 0.10-4.32). LIMITATIONS: Study population restricted to 11 trials, all having fewer than 200 patients each with a limited number of clinical events. CONCLUSIONS: Results of this analysis offer novel evidence supporting the use of an early reduction in proteinuria as a surrogate end point for clinical end points in IgAN in selected settings.

Inhaled colistimethate sodium in patients with bronchiectasis and Pseudomonas aeruginosa infection: results of PROMIS-I and PROMIS-II, two randomised, double-blind, placebo-controlled phase 3 trials assessing safety and efficacy over 12 months.

BACKGROUND: Chronic lung infection with Pseudomonas aeruginosa is associated with increased exacerbations and mortality in people with bronchiectasis. The PROMIS-I and PROMIS-II trials investigated the efficacy and safety of 12-months of inhaled colistimethate sodium delivered via the I-neb. METHODS: Two randomised, double-blind, placebo-controlled trials of twice per day colistimethate sodium versus placebo were conducted in patients with bronchiectasis with P aeruginosa and a history of at least two exacerbations requiring oral antibiotics or one requiring intravenous antibiotics in the previous year in hospitals in Argentina, Australia, Belgium, Canada, France, Germany, Greece, Israel, Italy, Netherlands, New Zealand, Poland, Portugal, Spain, Switzerland, the UK, and the USA. Randomisation was conducted through an interactive web response system and stratified by site and long term use of macrolides. Masking was achieved by providing colistimethate sodium and placebo in identical vials. After random assignment, study visits were scheduled for 1, 3, 6, 9, and 12 months (the end of the treatment period); and telephone calls were scheduled for 7 days after random assignment and 2 weeks after the end of treatment. The primary endpoint was the mean annual exacerbation rate. These trials are registered with EudraCT: number 2015-002743-33 (for PROMIS-I) and 2016-004558-13 (for PROMIS-II), and are now completed. FINDINGS: 377 patients were randomly assigned in PROMIS-I (177 to colistimethate sodium and 200 to placebo; in the modified intention-to-treat population, 176 were in the colistimethate sodium group and 197 were in the placebo group) between June 6, 2017, and April 8, 2020. The annual exacerbation rate was 0·58 in the colistimethate sodium group versus 0·95 in the placebo group (rate ratio 0·61; 95% CI 0·46-0·82; p=0·0010). 287 patients were randomly assigned in PROMIS-II (152 were assigned to colistimethate sodium and 135 were assigned to placebo, in the modified intention-to-treat population), between Feb 12, 2018, and Oct 22, 2021. PROMIS-II was then prematurely terminated due to the effect of the COVID-19 pandemic. No significant difference was observed in the annual exacerbation rate between the colistimethate sodium and placebo groups (0·89 vs 0·89; rate ratio 1·00; 95% CI 0·75-1·35; p=0·98). No major safety issues were identified. The overall frequency of adverse events was 142 (81%) patients in the colistimethate sodium group versus 159 (81%) patients in the placebo group in PROMIS-I, and 123 (81%) patients versus 104 (77%) patients in PROMIS-II. There were no deaths related to study treatment. INTERPRETATION: The data from PROMIS-I suggest a clinically important benefit of colistimethate sodium delivered via the I-neb adaptive aerosol delivery system in patients with bronchiectasis and P aeruginosa infection. These results were not replicated in PROMIS-II, which was affected by the COVID-19 pandemic and prematurely terminated. FUNDING: Zambon.

Hexasodium fytate for the treatment of calciphylaxis: a randomised, double-blind, phase 3, placebo-controlled trial with an open-label extension.

Background: In the CALCIPHYX trial, we investigated hexasodium fytate, an inhibitor of vascular calcification, for the treatment of calcific uraemic arteriolopathy (calciphylaxis), a rare condition characterised by painful, non-healing skin lesions. Methods: In this international, phase 3, randomised, double-blind, placebo-controlled trial, adults with an ulcerated calciphylaxis lesion and pain visual analogue scale (VAS) score ≥50/100 were randomised 1:1 to hexasodium fytate 7 mg/kg or placebo intravenously during maintenance haemodialysis. Primary efficacy outcomes were an 8-item modification of the Bates-Jensen Wound Assessment Tool (BWAT-CUA) and Pain VAS in the intention-to-treat population. ClinicalTrials.gov number: NCT04195906. Findings: Overall, 34/37 patients randomised to hexasodium fytate and 26/34 patients randomised to placebo completed the 12-week randomised treatment period. At Week 12, both groups (hexasodium fytate versus placebo) showed similar improvements in BWAT-CUA (mean [standard deviation (SD)], -5.3 [5.2] versus -6.0 [6.2]; least squares mean difference, 0.3 [96% confidence interval (CI): -2.5, 3.0]; p = 0.88) and Pain VAS (mean [SD], -19.5 [26.9] versus -32.2 [38.5]; least squares mean difference, 11.5 [96% CI: -4.8, 27.8]; p = 0.15). One patient randomised to placebo briefly received hexasodium fytate in error. Serious adverse events through Week 12 included: calciphylaxis-related events leading to hospitalisation (2/38 [5%] versus 11/33 [33%]) and death (1/38 [3%] versus 5/33 [15%]). During the subsequent 12 weeks of open-label hexasodium fytate and 4 weeks of follow-up, there were no additional calciphylaxis-related events leading to hospitalisation. Over the course of the entire trial, deaths were 2/38 [5%] for the hexasodium fytate group and 7/33 [21%] for the placebo group. Interpretation: In patients with calciphylaxis, BWAT-CUA and Pain VAS improved similarly in hexasodium fytate- and placebo-treated patients; over the course of the entire trial, there were fewer deaths and calciphylaxis-related events leading to hospitalisation in the hexasodium fytate group. Funding: Funded by Sanifit, a CSL Vifor company.

Decision making from Phase II to Phase III and the probability of success: reassured by "assurance"?

With Phase III failure rates of 50%, better ways of predicting late-stage success are needed. One concept that has been used is "assurance." Rather than conventional power calculations hypothesizing a known effect of a drug, assurance provides an expected power calculation based on some prior distribution for the treatment effect. It therefore has appeal in Phase III planning and decision making, especially when the prior is based on Phase II data. However, assurance has counterintuitive properties that can serve to confuse and concern the nonstatistician. Appreciation of these properties is helpful to ensure an informed use of assurance in strategic drug development.

The CALCIPHYX study: a randomized, double-blind, placebo-controlled, Phase 3 clinical trial of SNF472 for the treatment of calciphylaxis.

BACKGROUND: Calcific uraemic arteriolopathy (CUA; calciphylaxis) is a rare disease seen predominantly in patients receiving dialysis. Calciphylaxis is characterized by poorly healing or non-healing wounds, and is associated with mortality, substantial morbidity related to infection and typically severe pain. In an open-label Phase 2 clinical trial, SNF472, a selective inhibitor of vascular calcification, was well-tolerated and associated with improvement in wound healing, reduction of wound-related pain and improvement in wound-related quality of life (QoL). Those results informed the design of the CALCIPHYX trial, an ongoing, randomized, placebo-controlled, Phase 3 trial of SNF472 for treatment of calciphylaxis. METHODS: In CALCIPHYX, 66 patients receiving haemodialysis who have an ulcerated calciphylaxis lesion will be randomized 1:1 to double-blind SNF472 (7 mg/kg intravenously) or placebo three times weekly for 12 weeks (Part 1), then receive open-label SNF472 for 12 weeks (Part 2). All patients will receive stable background care, which may include pain medications and sodium thiosulphate, in accordance with the clinical practices of each site. A statistically significant difference between the SNF472 and placebo groups for improvement of either primary endpoint at Week 12 will demonstrate efficacy of SNF472: change in Bates-Jensen Wound Assessment Tool-CUA (a quantitative wound assessment tool for evaluating calciphylaxis lesions) or change in pain visual analogue scale score. Additional endpoints will address wound-related QoL, qualitative changes in wounds, wound size, analgesic use and safety. CONCLUSIONS: This randomized, placebo-controlled Phase 3 clinical trial will examine the efficacy and safety of SNF472 in patients who have ulcerated calciphylaxis lesions. Patient recruitment is ongoing.

Safety of formoterol in patients with asthma: combined analysis of data from double-blind, randomized controlled trials.

BACKGROUND: Concerns exist that regular long-acting beta(2)-adrenergic agonist (LABA) therapy may increase the risk of serious asthma-related events. OBJECTIVE: To assess risks of formoterol-containing versus non-LABA treatment by using a large asthma database. METHODS: This analysis included all blind, parallel-arm, randomized, active-controlled and/or placebo-controlled AstraZeneca-sponsored asthma studies with formoterol-containing and non-LABA comparator arms. Serious adverse events were assessed for inclusion in all-cause death, asthma-related death, asthma-related intubation, and asthma-related hospitalization categories by using blind adjudication. Data were combined across trials; relative risk (RR) was assessed by using Mantel-Haenszel methods. RESULTS: Data were from 13,542 formoterol-randomized and 9968 non-LABA patients 4 years or older (42 trials), of whom 93% and 89%, respectively, received inhaled corticosteroid as part of randomized treatment or allowed medication. Incidence of all-cause death was low (n=3 and n=4, respectively), with numerically lower all-cause deaths/1000 patient-treatment years in the formoterol-treated group (0.53) versus the non-LABA group (0.82) (RR, 0.64; 95% confidence interval [CI], 0.14-2.92). No asthma-related deaths and 1 asthma-related intubation (formoterol-treated group) occurred. Asthma-related hospitalizations/1000 patient-treatment years were lower numerically in the formoterol-treated group (12.1) versus the non-LABA group (16.4) (RR, 0.73; 95% CI, 0.54-1.01), with fewer study discontinuations in the formoterol-treated group (12.7% vs 15.4%, respectively; RR, 0.79; 95% CI, 0.74-0.85). Relative to non-LABA, increasing daily formoterol dose (>/=4.5, 9, 18, 36 mug) did not increase the rate or incidence of asthma-related hospitalization. CONCLUSION: No evidence of increased risk of asthma-related hospitalization, no asthma-related deaths, and a low incidence of all-cause death and asthma-related intubation were seen with formoterol-containing versus non-LABA treatment.

Back to basics: explaining sample size in outcome trials, are statisticians doing a thorough job?

Time to event outcome trials in clinical research are typically large, expensive and high-profile affairs. Such trials are commonplace in oncology and cardiovascular therapeutic areas but are also seen in other areas such as respiratory in indications like chronic obstructive pulmonary disease. Their progress is closely monitored and results are often eagerly awaited. Once available, the top line result is often big news, at least within the therapeutic area in which it was conducted, and the data are subsequently fully scrutinized in a series of high-profile publications. In such circumstances, the statistician has a vital role to play in the design, conduct, analysis and reporting of the trial. In particular, in drug development it is incumbent on the statistician to ensure at the outset that the sizing of the trial is fully appreciated by their medical, and other non-statistical, drug development team colleagues and that the risk of delivering a statistically significant but clinically unpersuasive result is minimized. The statistician also has a key role in advising the team when, early in the life of an outcomes trial, a lower than anticipated event rate appears to be emerging. This paper highlights some of the important features relating to outcome trial sample sizing and makes a number of simple recommendations aimed at ensuring a better, common understanding of the interplay between sample size and power and the final result required to provide a statistically positive and clinically persuasive outcome.

The epidemiology of Shiga toxin-producing Escherichia coli infections in the South East of England: November 2013-March 2017 and significance for clinical and public health.

PURPOSE: This study describes the epidemiology of Shiga toxin-producing Escherichia coli (STEC) infections in a population in the South East of England. METHODS: From 1 November 2013 to 31 March 2017 participating diagnostic laboratories reported Shiga toxin gene (stx) positive real-time PCR results to local public health teams. Stx positive faecal samples/isolates were referred to the Gastrointestinal Bacteria Reference Unit (GBRU) for confirmation by culture and typing by whole genome sequencing (WGS). Key clinical information was collected by public health teams.Results/Key findings. Altogether, 548 faecal specimens (420 were non-travel associated) were stx positive locally, 535 were submitted to the GBRU. STEC were isolated from 42 %, confirmed by stx PCR in 21 % and 37 % were PCR negative. The most common non-travel associated STEC serogroups were O157, O26, O146 and O91. The annualized incidence of confirmed STEC infections (PCR or culture) was 5.8 per 100 000. The ratio of O157 to non-O157 STEC serogroups was 1:7. The annualized incidence of non-O157 haemolytic uraemic syndrome-associated Escherichia coli (HUSEC) strains was 0.4 per 100 000. Bloody diarrhoea was reported by 58 % of cases infected with E. coli O157, 33 % of cases infected with non-O157 HUSEC strains and 12 % of other lower risk non-O157 strains. Overall, 76 % of non-O157 HUSEC isolates possessed the eae virulence gene. CONCLUSIONS: HUSEC including serogroup O157 were uncommon and more likely to cause bloody diarrhoea than other STEC. The routine use of stx PCR testing can influence clinical management. Understanding the local epidemiology facilitates a proportionate public health response to STEC, based on clinical and microbiological characteristics including stx subtype(s).

Improvement in wound healing, pain, and quality of life after 12 weeks of SNF472 treatment: a phase 2 open-label study of patients with calciphylaxis.

BACKGROUND: Calciphylaxis in end-stage renal disease is characterized by painful necrotic skin ulcers and high mortality. There are no approved therapies. SNF472, an intravenous formulation of myo-inositol hexaphosphate, inhibits the formation and growth of hydroxyapatite crystals, the final common pathway in the pathogenesis of vascular calcification. METHODS: In this open-label, single-arm study, calciphylaxis patients on thrice-weekly hemodialysis and standard care, received intravenous SNF472 3 times per week for 12 weeks. The primary endpoint was wound healing assessed using the quantitative Bates-Jensen Wound Assessment Tool (BWAT). Pain visual analog scale (VAS), quality of life (wound-QoL), and qualitative wound image review were secondary endpoints. Quantitative changes from baseline were analyzed by paired t-tests using multiple imputation to account for missing observations. RESULTS: Fourteen patients received SNF472. Improvements from baseline to week 12 were observed for mean BWAT score (- 8.1; P < 0.001), pain VAS (- 23.6 mm; P = 0.015) and wound-QoL global score (- 0.90; P = 0.003). Of the 9 patients with ulcerated lesions at baseline who completed treatment, wound image review showed improvement for 7. SNF472 was well tolerated with no serious treatment-related adverse events. The most common adverse events were infections which occur frequently in patients on hemodialysis. None of these were considered as treatment-related. CONCLUSIONS: SNF472 was well-tolerated and improvements from baseline to week 12 in wound healing, pain, and quality of life were observed. A randomized, double-blind, placebo-controlled trial is planned to evaluate SNF472 in patients with calciphylaxis.

Is prostate-specific antigen a valid surrogate end point for survival in hormonally treated patients with metastatic prostate cancer? Joint research of the European Organisation for Research and Treatment of Cancer, the Limburgs Universitair Centrum, and AstraZeneca Pharmaceuticals.

PURPOSE: The long duration of phase III clinical trials of overall survival (OS) slows down the treatment-development process. It could be shortened by using surrogate end points. Prostate-specific antigen (PSA) is the most studied biomarker in prostate cancer (PCa). This study attempts to validate PSA end points as surrogates for OS in advanced PCa. PATIENTS AND METHODS: Individual data from 2,161 advanced PCa patients treated in studies comparing bicalutamide to castration were used in a meta-analytic approach to surrogate end-point validation. PSA response, PSA normalization, time to PSA progression, and longitudinal PSA measurements were considered. RESULTS: The known association between PSA and OS at the individual patient level was confirmed. The association between the effect of intervention on any PSA end point and on OS was generally low (determination coefficient, < 0.69). CONCLUSION: It is a common misconception that high correlation between biomarkers and true end point justify the use of the former as surrogates. To statistically validate surrogate end points, a high correlation between the treatment effects on the surrogate and true end point needs to be established across groups of patients treated with two alternative interventions. The levels of association observed in this study indicate that the effect of hormonal treatment on OS cannot be predicted with a high degree of precision from observed treatment effects on PSA end points, and thus statistical validity is unproven. In practice, non-null treatment effects on OS can be predicted only from precisely estimated large effects on time to PSA progression (TTPP; hazard ratio, < 0.50).