Abstract
Background Despite evidence of selective outcome reporting across multiple disciplines, this has not yet been assessed in trials studying the effects of exercise in people with cancer. Therefore, the purpose of our study was to explore prospectively registered randomised controlled trials (RCTs) in exercise oncology for evidence of selective outcome reporting.
Methods Eligible trials were RCTs that 1) investigated the effects of at least partially supervised exercise interventions in people with cancer; 2) were preregistered (i.e. registered before the first patient was recruited) on a clinical trials registry; and 3) reported results in a peer-reviewed published manuscript. We searched the PubMed database from the year of inception to September 2020 to identify eligible exercise oncology RCTs clinical trial registries. Eligible trial registrations and linked published manuscripts were compared to identify the proportion of sufficiently preregistered outcomes reported correctly in the manuscripts, and cases of outcome omission, switching, and silently introduction of non-novel outcomes.
Results We identified 31 eligible RCTs and 46 that were ineligible due to retrospective registration. Of the 405 total prespecified outcomes across the 31 eligible trials, only 6.2% were preregistered complete methodological detail. Only 16% (n=148/929) of outcomes reported in published results manuscripts were linked with sufficiently preregistered outcomes without outcome switching. We found 85 total cases of outcome switching. A high proportion (41%) of preregistered outcomes were omitted from the published results manuscripts, and many published outcomes (n=394; 42.4%) were novel outcomes that had been silently introduced (median, min-max=10, 0-50 per trial). We found no examples of preregistered efficacy outcomes that were measured, assessed, and analysed as planned.
Conclusions We found evidence suggestive of widespread selective outcome reporting and non-reporting bias (outcome switching, omitted preregistered outcomes, and silently introduced novel outcomes). The existence of such reporting discrepancies has implications for the integrity and credibility of RCTs in exercise oncology.
Preregistered protocol https://osf.io/dtkar/ (posted: November 19, 2019)
Competing Interest Statement
BS, CMF, JFC, KAB, RT, DN, and IML have ties to some of the authors of the included studies. CMF, JFC, KAB, RT, DN, and IML have given talks on the role of exercise in patients with cancer at workshops, seminars, and conferences for which travel and accommodation was paid for by the organisers. DN has received expenses and fees for his media work and teaching workshops on Evidence-based Medicine for the Centre of Evidence Based Medicine, and is a lead member of the Royal College of General Practioners Physical Activity Clinical Priority group.
Clinical Trial
Preregistered protocol: https://osf.io/dtkar/
Clinical Protocols
Funding Statement
We received no external funding for this project.
Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
This is a cross-sectional study of published trials in exercise oncology, and therefore, did not require ethical approval.
All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.
Yes
I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).
Yes
I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.
Yes
Data Availability
All data and analysis code are available at: https://osf.io/4c8mb/ and data we extracted from the individual trials can be accessed here: https://bit.ly/3qFkcro
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