Can Observational Data Replace Randomized Trials?

McGale, Paul; Cutter, David J.; Darby, Sarah C.; Henson, Katherine E; Jagsi, Reshma; Taylor, Carolyn

doi:10.1200/jco.2016.68.8879

Cited by 34 publications

(27 citation statements)

References 2 publications

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“…For example, there have been many claims about the benefits of various vitamin supplements based on observational studies 128,129 that have been reliably refuted by large-scale randomized trials. [130][131][132] Similarly, when compared with the results from randomized trials of the effects of treatments for several different cancers, observational studies have generated improbable results despite controlling for comorbidity, extent of disease and many other characteristics that were recorded in detailed databases [133][134][135] (as is also the case for reported associations of statins with lower rates of cancer 90,[136][137][138] ). These findings are consistent with empirical studies in which biases in observational studies were shown to be large enough to conclude falsely that treatment produced benefit or harm, with none of a range of statistical strategies (such as regression analysis or propensity matching) capable of adjusting adequately or predictably for bias.…”

Section: Biases Due To Differences In Underlying Risks Of Health Outcmentioning

confidence: 99%

Interpretation of the evidence for the efficacy and safety of statin therapy

et al. 2016

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms SummaryThis review is intended to help clinicians, patients and the public make informed decisions about statin therapy for the prevention of heart attacks and strokes. It explains how the evidence that is available from randomized controlled trials yields reliable information about both the efficacy and safety of statin therapy. In addition, it discusses how claims that statins commonly cause adverse effects reflect a failure to recognise the limitations of other sources of evidence about the effects of treatment.Large-scale randomized trial evidence shows that statin therapy reduces the risk of heart attacks, ischaemic strokes and coronary revascularization procedures ("major vascular events") by about one quarter for each mmol/L reduction in low density lipoprotein (LDL) cholesterol during each year (after the first) that it continues to be taken. The absolute benefits of statin therapy depend on an individual's absolute risk of occlusive vascular events and the absolute reduction in LDL cholesterol that is achieved. For example, lowering LDL cholesterol by 2 mmol/L (77 mg/dL) with an effective low-cost statin regimen (e.g. atorvastatin 40 mg daily, costing about £2 per

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Section: Biases Due To Differences In Underlying Risks Of Health Outcmentioning

confidence: 99%

Interpretation of the evidence for the efficacy and safety of statin therapy

et al. 2016

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“…The results have to be interpreted with caution, as any retrospective approach has inherent limitations: As known from other observational studies [ 15 , 29 ], outcome in clinical effectiveness research is influenced by a number of unmeasured confounding factors and associations between treatments, and outcomes can result from confounding and have no causal correlation [ 30 , 31 ]. We tried to control for all known confounders available in the registry, which may have influenced the clinical treatment decision-making process.…”

Section: Discussionmentioning

confidence: 99%

Role of postoperative radiotherapy in reducing ipsilateral recurrence in DCIS: an observational study of 1048 cases

et al. 2018

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BackgroundThe objective of the present study was to evaluate the effectiveness of postoperative radiotherapy after breast conserving surgery (BCS) in DCIS in a large patient population treated in clinical practice.MethodsData were provided by the population-based Munich Cancer Registry. Between 1998 and 2014, 1048 female patients with diagnosis of DCIS and treated at two Breast Care Centres were included in this observational study. The effectiveness of postoperative radiotherapy and variables predicting the use of radiotherapy were retrospectively analysed.ResultsAfter adjusting for age, tumour characteristics and therapies, Cox regression analysis for local recurrence-free survival identified RT as an independent predictor for improved local control (HR: 0.579; 95%CI: 0.384–0.872, p = 0.008). Ten-year cumulative incidence of in-breast recurrences was 20.0% following BCS, compared to 13.6% in patients receiving postoperative radiotherapy (p = 0.012). As an estimate for disease-specific survival, 10-year relative survival was 105.4% for patients receiving postoperative radiotherapy and 101.6% without radiotherapy. On multivariate analysis, postoperative radiotherapy was not associated with improved overall survival (HR 0.526; 95%CI: 0.263–1.052, p = 0.069). Over time, a significant increase of RT was registered: while 1998 only 42.9% of patients received postoperative radiotherapy, the proportion rose to 91.2% in 2014. Women aged < 50 years (OR: 2.559, 95%CI: 1.416–4.625, p < 0.001) or with negative hormone receptor status (OR: 2.625, 95%CI: 1.458–4.728, p = 0.001) or receiving endocrine therapy (OR: 1.762, 95%CI: 1.060–2.927, p = 0.029) were more likely to receive postoperative radiotherapy after BCS.ConclusionsIn conclusion, this study provides insights regarding the adoption and treatment pattern of postoperative RT following BCS for DCIS in a large cohort reflecting “real-life” clinical practice in this setting. Postoperative RT was found to be associated with a reduced risk of ipsilateral recurrence and no survival benefit compared to observation alone.

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“…Even though routine clinical care might become a cornucopia of clinical data, this data needs to be handled with care: McGale et al [18] show that conclusions from routine clinical care data may contradict findings from randomized clinical trials. Routine care data is subject to many biases contrary to data from carefully designed trials.…”

Section: Resultsmentioning

confidence: 99%