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BackgroundA better understanding of the current characteristics of clinical trials on thyroid cancer (TC) is important to improve trial designs and identify neglected areas of research. However, there is a lack of a thorough understanding of the clinical studies on TC. Therefore, this study aimed to present a comprehensive overview of clinical trials on TC based on the ClinicalTrials.gov database and evaluate their publication status.MethodsWe searched for TC-related clinical studies registered in the ClinicalTrials.gov database before December 2018 by using the keyword “thyroid cancer” and assessed the characteristics of the included trials. We searched the publication status of primary completed studies in PubMed and Google Scholar.ResultsA total of 450 studies were identified for analysis, including 333 (74.0%) interventional studies and 117 (26.0%) observational studies. Interventional studies about TC were commonly non-randomized (67.6%), single-arm (55.6%), single-center (76.3%), and early-phase (60.0%) trials. The major category for which studies were performed was for target drug-related therapy (53.6%). In addition, 57.0% of the primary completed interventional studies were published. The published studies were more commonly primary completed studies after 2010 and used randomization and were less commonly designed as single-arm studies and were conducted in the USA/Canada, compared to non-published studies (P < 0.05 for all). The median time from primary completion to publication was 46.5 months, and the time decreased to 36.5 months after 2010. Studies conducted in the USA/Canada [odds ratio (OR) = 9.43, P = 0.020] and multi-center studies (OR = 6.55, P = 0.021) significantly increased the potential of publication in high-impact journals.ConclusionsHigh-quality, randomized phase 3 trials regarding TC are still insufficient. Therefore, more efforts are needed to improve the treatment of poor prognostic TC and timely publication.

A better understanding of the current features of type 2 diabetes mellitus (T2DM)related clinical trials is important for improving designs of clinical trials and identifying neglected areas of research. It was hypothesized that the trial registration policy promoted the designs of T2DM-related trials over the years. Therefore, this study aimed to present a comprehensive overview of T2DM-related clinical trials registered in the ClinicalTrials.gov database. Methods: T2DM-related clinical trials registered in the ClinicalTrials.gov database were searched and assessed the characteristics of the relevant trials. We searched PubMed and Google Scholar for the publication statuses of the primary completed trials. Results: Overall, 5117 T2DM-related trials were identified for analysis. Of the interventional trials, 71.5% had a primary treatment purpose while only 8.9% were prevention or health service. There were more interventional trials registered prior to patient recruitment between 2012 and 2019 than between 2004 and 2011 (44.6% vs 19.9%, P<0.001). The period between 2012 and 2019 also had more trials that enrolled <100 participants (59.2% vs 50.9%), were single-center studies (60.7% vs 50.6%), had non-randomized allocations (11.3% vs 6.3%), were open-label (49.2% vs 45.6%), and had smaller sample sizes than the period between 2004 and 2011 (all P<0.001). The five-year cumulative publication rates after primary completion of the trials were <40%. Conclusion: Although the ClinicalTrials.gov database did not include all clinical trials, the trials registered in the ClinicalTrials.gov database still accounted for most of the clinical studies. Encouragingly, more interventional trials were registered prior to patient recruitment over the years. The majority of T2DM-related clinical trials focused on drug-related treatment, and trials regarding prevention in T2DM should be promoted. More attention should be paid to improve the publication and dissemination of clinical trials results.

Background: We sought to investigate the methodological and reporting quality of published systematic reviews describing randomized controlled trials in type 2 diabetes mellitus and analyze their association with status of protocol registration.Methods: We searched the PubMed database and identified non-Cochrane systematic reviews, with or without meta-analysis, reporting on type 2 diabetes mellitus and published between 2005 and 2018. We then randomly selected 20% of these reviews in each year, and performed methodological and reporting quality assessment using the Assessment of Multiple Systematic Review 2 (AMSTAR-2) checklist and Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. We also conducted regression analyses to explore the association between characteristics of systematic reviews and AMSTAR-2 or PRISMA scores.Results: A total of 238 systematic reviews, including 33 registered and 205 non-registered articles, met the inclusion criteria and were subsequently reviewed. Analysis indicated an increase in both registered rates and quality of systematic reviews in type 2 diabetes mellitus over the recent years. With regards to methodological and reporting quality, we found higher scores in registered, relative to non-registered reviews (AMSTAR-2 mean score: 18.0 vs. 14.5, P = 0.000; PRISMA mean score: 20.4 vs. 17.6, P = 0.000). AMSTAR-2 and PRISMA scores were associated with registration status, country of the first author, and statistical results, whereas the proportion of discussing publication bias and reporting funding sources were &lt;40% for both registered and non-registered systematic reviews.Conclusions: Methodological and reporting quality of systematic reviews in type 2 diabetes mellitus indicates an improvement in the recent years. However, the overall quality remains low, necessitating further improvement. Future studies are expected to pay more attention to prospective registration, description of publication bias and reporting of funding sources.

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