Meta-analyses versus randomised controlled trials in intensive care medicine

Use of a random effects meta-analysis in the design and analysis of a new clinical trial

In designing a randomized controlled trial, it has been argued that trialists should consider existing evidence about the likely intervention effect. One approach is to form a prior distribution for the intervention effect based on a meta‐analysis of previous studies and then power the trial on its ability to affect the posterior distribution in a Bayesian analysis. Alternatively, methods have been proposed to calculate the power of the trial to influence the “pooled” estimate in an updated meta‐analysis. These two approaches can give very different results if the existing evidence is heterogeneous, summarised using a random effects meta‐analysis. We argue that the random effects mean will rarely represent the trialist's target parameter, and so, it will rarely be appropriate to power a trial based on its impact upon the random effects mean. Furthermore, the random effects mean will not generally provide an appropriate prior distribution. More appropriate alternatives include the predictive distribution and shrinkage estimate for the most similar study. Consideration of the impact of the trial on the entire random effects distribution might sometimes be appropriate. We describe how beliefs about likely sources of heterogeneity have implications for how the previous evidence should be used and can have a profound impact on the expected power of the new trial. We conclude that the likely causes of heterogeneity among existing studies need careful consideration. In the absence of explanations for heterogeneity, we suggest using the predictive distribution from the meta‐analysis as the basis for a prior distribution for the intervention effect.

A Phase III Randomized Study Comparing a Chemotherapy with Cisplatin and Etoposide to a Etoposide Regimen without Cisplatin for Patients with Extensive Small-Cell Lung Cancer

Introduction

In a literature meta-analysis, we showed survival benefits for regimens including cisplatin [hazard ratio (HR) 0.61; 95% confidence interval (CI), 0.57–0.66] and for those including etoposide (HR 0.65; 0.61–0.69). That benefit was mainly observed when etoposide alone or in combination with cisplatin was included in the chemotherapy regimens. Our objective was to determine if chemotherapy with both drugs improves survival in comparison to a non-platinum regimen with etoposide.

Methods

Extensive small-cell lung cancer patients were randomized between cisplatin–etoposide (CE) and ifosfamide + etoposide + epirubicin regimen (IVE) between 2000 and 2013.

Results

176 and 170 eligible patients were allocated to CE and IVE (315 deaths were required before analysis), respectively. Objective response rates were not significantly different: 60% with CE and 59% with IVE. No statistically significant difference in median survival and 1-year and 2-year was observed with rates of 9.6 months, 31 and 5% for CE and 10 months, 39 and 9% for IVE, respectively. HR was 0.84 (95% CI 0.68–1.05, p = 0.16). Only two prognostic factors for survival were retained in multivariate analysis: sex with HR = 0.69 (95% CI 0.49–0.97, p = 0.03) and performance status with HR = 0.53 (95% CI 0.49–0.97, p < 0.0001). After adjustment for these prognostic factors, HR for survival was 0.83 (95% CI 0.65–1.08, p = 0.17). There was more thrombopenia in the CE regimen and more leukopenia with IVE.

Conclusion

Combination of CE failed to improve survival in comparison to an etoposide-containing regimen without cisplatin.

Clinical Trial Registration

https://clinicaltrials.gov/ct2/show/NCT00658580?term=ELCWP+01994&rank=1, identifier NCT00658580.

Immunonutrition in septic patients: A philosophical view of the current situation

BACKGROUND & AIMS

Two different ways of thinking pervaded the history of science: rationalism and empiricism. In theory, these two paradigms are not necessarily in conflict. In practice, there has always been tension between them. The coming of evidence-based medicine put empiricism in a privileged position, but empiricism without a rationalistic guide could even be usefulness. The aim of this work is to present the tension between the rational reasons to administer immunonutrients to patients with sepsis and the controversial empirical evidence stemming from clinical trials.

METHODS

We reviewed the literature on immunonutrition in sepsis from the rationalist and the empiricist perspectives.

RESULTS

The large body of evidence for positive effects of immunonutrients in experimental models and the contradictory results from clinical trials make the discussion on immunonutrition in sepsis a typical example where the conflict between rationalism and empiricism hampered the advancement of knowledge and the implementation of new effective therapies into clinical practice.

CONCLUSIONS

Future research projects involving immunonutrients should be based on robust knowledge of basic mechanisms of action to be properly addressed in clinical trials.

Evidence-based medicine in intensive care

The life-threatening nature of critical illness, requiring simultaneous, multiple interventions, makes it difficult, if not impossible, to study the effects of any one treatment. It is often not possible to conduct trials in critically ill patients, as they can not give informed consent. Some high quality, prospective studies have influenced clinical practice in intensive care, but others with lower grades of evidence have led to some controversy. In intensive care, clinical practice is still influenced by a combination of theory, experience and evidence.

Systematic reviews of nursing research

As a result of the rapid advances in technology and the large volume of literature, healthcare decisions have become more complex. In response to this, increasing emphasis has been placed on basing these decisions on the best available research evidence. Systematic reviews are now accepted as the most reliable way by which this large volume of research evidence can be managed. These reviews follow the same principles expected of any research endeavour. This includes documentation of methods prior to commencement, comprehensive search to identify all studies on the topic, and the use of rigorous methods for the appraisal, collection and synthesis of data. On completion of the review, the methods used are reported to allow its validity to be evaluated by end users of the evidence.