An epidemic of redundant meta-analyses

The redundant landscape of meta-analyses: Evaluating exercise interventions for older adults with cognitive impairment

BACKGROUND

Exercise to benefit cognition in older adults with cognitive impairment is well-studied. A recent proliferation of synthesis studies might be a positive contribution to the science; however, redundancy in research can be wasteful and detrimental to drawing confident conclusions about the evidence. This synthesis-based method study was designed to analyze: 1) the frequency and growth patterns of meta-analyses (MAs) and randomized controlled trials (RCTs) on this topic; and 2) the redundancy rate of the RCT studies included in MAs.

METHODS

This study was borne of a living systematic review, following standard synthesis methodology (PROSPERO registration, librarian-assisted search algorithms developed for multiple databases, searches updated regularly with most recent search in 2025). Frequency counts determined the number of RCTs and how many times they were included across the MAs.

RESULTS

Forty MAs were identified and included in the synthesis representing a total of 728 RCT studies. After reviewing RCT duplicates, 276 (37.9%) unique RCT studies comprised this body of evidence. Among these, 153 RCTs were cited in only one MA and 123 were cited in 2-19 different MAs. Thus, 452 (62.1%) of all RCTs used across the 40 MAs were redundant (i.e., represented in more than one MA).

CONCLUSIONS

This study found substantial redundancy in the RCTs used in MAs evaluating the cognitive impact of exercise for older adults with cognitive impairment. Replication is common practice in research but reliance on the same RCTs in multiple MAs creates an illusion of robustness when, in fact, the strength and diversity of the evidence may be more limited. Research redundancy is wasteful and may actually stagnate advancement of this science.

Thrombosis, Translational Medicine, and Biomarker Research: Moving the Needle

Arterial and venous thromboembolism are leading causes of morbidity and death worldwide. Despite significant advances in the diagnosis, prognostication, and treatment of thrombotic diseases over the past 3 decades, the adoption of findings stemming from translational biomarker research in clinical practice remains limited. Biomarkers provide an opportunity to enhance our understanding of pathophysiological processes and optimize treatment strategies. They hold the promise of revolutionizing patient care. Still, this potential remains untapped, and several factors impede their use for near-patient applications. We sought to provide an overview of biomarker research in arterial and venous thromboembolic disease. We then aimed to discuss key barriers to the broader clinical implementation of biomarker research and highlight promising strategies to overcome them. We emphasize the merits of translational and implementation science to bridge the gaps from bench to bedside. Innovative trial design, data sharing, and collaborative efforts between academia and industry will be essential. Purposeful regression methodology using rational conceptual framework design, causal mediation analysis, and artificial intelligence might better leverage the use of observational data. Dedicated translational science training programs geared toward educating physicians on the appropriate measurement, interpretation, and integration of biomarker data in clinical practice should foster endorsement by frontline physicians. Finally, we make the case in support of a paradigm shift in cardiovascular medicine. Improved recognition of biomarker research and a greater emphasis on mechanistic evidence can better equip clinicians to deal with the uncertainty that defines the practice of thrombosis medicine.

Antithrombotic Therapy in Cancer Patients with Cardiovascular Diseases: Daily Practice Recommendations by the Hemostasis Working Party of the German Society of Hematology and Medical Oncology (DGHO) and the Society for Thrombosis and Hemostasis Research (GTH e.V.)

Active cancer by itself but also chemotherapy is associated with an increased risk of cardiovascular disease (CVD) and especially coronary artery disease (CAD) and atrial fibrillation (AF). The frequency of CVD, CAD, and AF varies depending on comorbidities (particularly in older patients), cancer type, and stage, as well as the anticancer therapeutic being taken. Many reports exist for anticancer drugs being associated with CVD, CAD, and AF, but robust data are often lacking. Because of this, each patient needs an individual structured approach concerning thromboembolic and bleeding risk, drug-drug interactions, as well as patient preferences to evaluate the need for anticoagulation therapy and targeting optimal symptom control. Interruption of specific cancer therapy should be avoided to reduce the potential risk of cancer progression. Nevertheless, additional factors like thrombocytopenia and anticoagulation in the elderly and frail patient with cancer cause additional challenges which need to be addressed in daily clinical management. Therefore, the aim of these recommendations is to summarize the available scientific data on antithrombotic therapy (both antiplatelet and anticoagulant therapy) in cancer patients with CVD and in cases of missing data providing guidance for optimal careful decision-making in daily routine.

The sound and surprise: overlapping meta-analyses on the topic of safety and efficacy of PD-1 and PD-L1 inhibitors in the treatment of non-small cell lung cancer

PURPOSE

To analyze the characteristics of overlapping meta-analyses based on randomized controlled trials (RCTs) which reported PD-1/PD-L1 inhibitors in non-small cell cancer (NSCLC).

METHODS

Meta-analyses were identified from English and Chinese databases until January 1, 2022. Differences in characteristics of overlapping meta-analyses that conducted in China and other countries were compared to assess their publication propensity. The corrected covered area (CCA) and coverage of relevant RCTs were analyzed for subtopics according to detailed intervention types. The waste and redundancy of evidence were assessed in the case of PD-1/PD-L1 inhibitor monotherapy for second-line treatment for NSCLC.

RESULTS

Fifty-nine meta-analyses published in English and 17 meta-analyses published in Chinese reporting 26 RCTs were identified. Fifty-three (69.74%) meta-analyses were conducted in China. The overlapping meta-analyses in China were more likely to be from hospitals, supported by government funding, integrate first and second-line therapies. Five of the six subtopics had overlapping meta-analyses according to specific types of interventions. The CCA of overlapping meta-analyses ranged from 33.33 to 63.19%, and the coverage of relevant RCTs ranged from 63.64 to 100%. All the conclusions of overlapping meta-analyses have been consistent in the subtopic of PD-1/PD-L1 inhibitor monotherapy for second-line treatment since 2017.

CONCLUSION

Overlapping meta-analyses of PD-1/PD-L1 inhibitors in NSCLC hints that meta-analyses under this topic probably exist serious redundancy. Future research should focus on prospective registration of protocols for systematic reviews/meta-analyses, scientific designed PICO, and cumulative meta-analysis to reduce redundant and wasted studies. Journals should strengthen the requirement for reviewing previously published evidence in manuscript review.

Replication of systematic reviews: is it to the benefit or detriment of methodological quality?

OBJECTIVES

To perform an overview of the overlap of systematic reviews (SRs) assessing direct oral anticoagulants and characterize these reviews in terms of bias and methodological quality (PROSPERO: CRD42022316273).

STUDY DESIGN AND SETTING

A PubMed-indexed search was performed from inception to January 31, 2022 to identify SRs evaluating direct oral anticoagulants in patients treated for an acute venous thromboembolism. The risk of bias of these SRs was assessed according to the Risk Of Bias In Systematic reviews tool. Redundancy was defined as overlap in terms of the type of population considered, the interventions compared, and the studies included.

RESULTS

A total of 144 SRs were evaluated, of which 26 (18.1%) were classified as original, 87 (60.4%) as conceptual replications, and 31 (21.5%) as excessive replications. The risk of bias was high in 19 (73.1%) of the original SRs, 65 (74.7%) of the conceptual replications, and 21 (67.7%) of the excessive replications. Compared to the original SRs, the overall methodological quality was not improved in either conceptual or excessive replications.

CONCLUSION

A large number of SRs was classified as replications; a fifth constituted excessive replications. The replications showed no improvement in overall methodological quality compared to the original SRs.

Framework for a living systematic review and meta-analysis for the surgical treatment of bladder cancer: introducing EVIglance to urology

Background

Knowledge of current and ongoing studies is critical for identifying research gaps and enabling evidence-based decisions for individualized treatment. However, the increasing number of scientific publications poses challenges for healthcare providers and patients in all medical fields to stay updated with the latest evidence. To overcome these barriers, we aim to develop a living systematic review and open-access online evidence map of surgical therapy for bladder cancer (BC), including meta-analyses.

Methods

Following the guidelines provided in the Cochrane Handbook for Systematic Reviews of Interventions and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement, a systematic literature search on uro-oncological therapy in BC will be performed across various literature databases. Within the scope of a meta-analysis and living systematic review, relevant randomized controlled trials will be identified. Data extraction and quantitative analysis will be conducted, along with a critical appraisal of the quality and risk of bias of each study. The available research evidence will be entered into an open-access framework (www.evidencemap.surgery) and will also be accessible via the EVIglance app. Regular semi-automatic updates will enable the implementation of a real-living review concept and facilitate resource-efficient screening.

Discussion

A regularly updated evidence map provides professionals and patients with an open-access knowledge base on the current state of research, allowing for decision-making based on recent evidence. It will help identify an oversupply of evidence, thus avoiding redundant work. Furthermore, by identifying research gaps, new hypotheses can be formulated more precisely, enabling planning, determination of sample size, and definition of endpoints for future trials.

Risk of drug use during pregnancy: master protocol for living systematic reviews and meta-analyses performed in the metaPreg project

BACKGROUND

Knowledge about the risks of drugs during pregnancy is continuously evolving due to the frequent publication of a large number of epidemiological studies. Systematic reviews and meta-analyses therefore need to be regularly updated to reflect these advances. To improve dissemination of this updated information, we developed an initiative of real-time full-scale living meta-analyses relying on an open online dissemination platform ( www.metapreg.org ).

METHOD

All living meta-analyses performed in this project will be conducted in accordance with this master protocol after adaptation of the search strategy. A systematic literature search of PubMed and Embase will be performed. All analytical studies (e.g., cohort, case-control, randomized studies) reporting original empirical findings on the association between in utero exposure to drugs and adverse pregnancy outcomes will be included. Study screening and data extraction will be performed in a semi-automation way supervised by a biocurator. A risk of bias will be assessed using the ROBINS-I tools. All clinically relevant pregnancy adverse outcomes (malformations, stillbirths, neuro-developmental disorders, pre-eclampsia, etc.) available in the included studies will be pooled through random-effects meta-analysis. Heterogeneity will be evaluated by I² statistics.

DISCUSSION

Our living systematic reviews and subsequent updates will inform the medical, regulatory, and health policy communities as the news results evolve to guide decisions on the proper use of drugs during the pregnancy.

SYSTEMATIC REVIEW REGISTRATION

Open Science Framework (OSF) registries.

Definition, harms, and prevention of redundant systematic reviews

BACKGROUND

Along with other types of research, it has been stated that the extent of redundancy in systematic reviews has reached epidemic proportions. However, it was also emphasized that not all duplication is bad, that replication in research is essential, and that it can help discover unfortunate behaviors of scientists. Thus, the question is how to define a redundant systematic review, the harmful consequences of such reviews, and what we could do to prevent the unnecessary amount of this redundancy.

MAIN BODY

There is no consensus definition of a redundant systematic review. Also, it needs to be defined what amount of overlap between systematic reviews is acceptable and not considered a redundancy. One needs to be aware that it is possible that the authors did not intend to create a redundant systematic review. A new review on an existing topic, which is not an update, is likely justified only when it can be shown that the previous review was inadequate, for example, due to suboptimal methodology. Redundant meta-analyses could have scientific, ethical, and economic questions for researchers and publishers, and thus, they should be avoided, if possible. Potential solutions for preventing redundant reviews include the following: (1) mandatory prospective registration of systematic reviews; (2) editors and peer reviewers rejecting duplicate/redundant and inadequate reviews; (3) modifying the reporting checklists for systematic reviews; (4) developing methods for evidence-based research (EBR) monitoring; (5) defining systematic reviews; (6) defining the conclusiveness of systematic reviews; (7) exploring interventions for the adoption of methodological advances; (8) killing off zombie reviews (i.e., abandoned registered reviews); (9) better prevention of duplicate reviews at the point of registration; (10) developing living systematic reviews; and (11) education of researchers.

CONCLUSIONS

Disproportionate redundancy of the same or very similar systematic reviews can lead to scientific, ethical, economic, and societal harms. While it is not realistic to expect that the creation of redundant systematic reviews can be completely prevented, some preventive measures could be tested and implemented to try to reduce the problem. Further methodological research and development in this field will be welcome.

Kanglaite (Coix Seed Extract) as Adjunctive Therapy in Cancer: Evidence Mapping Overview Based on Systematic Reviews With Meta-Analyses

Background: Several quantitative systematic reviews of Kanglaite (KLT), an herb preparation used to treat cancer and malignant pleural effusion, have been published in recent years. However, the clinical evidence reported in these studies has not been pursued further and the methodological quality of these meta-analyses remains unknown. Therefore, an overview was designed to map the evidence landscape based on the published meta-analyses on KLT in cancer treatment. Methods: Two bibliographic databases (PubMed and Embase) were searched from inception to 25 November 2021. Two independent reviewers were involved in study selection, data abstraction, and methodological quality assessment using AMSTAR 2. The principal features of publications and the clinical outcomes of efficacy and safety were synthesized narratively, and results of methodological quality were reported as frequencies and percentages with the corresponding 95% confidence intervals. The evidence map was used to visualize the overall quality. Excel 2016 and Stata 17/SE were used for data analysis. Results: Thirteen meta-analyses published in English were included for in-depth analysis. Among them, the year of publication ranged from 2008 to 2021, and the number of included patients ranged from 488 to 2,964. Regarding the cancer type, seven articles focused on non-small cell lung cancer, two on malignant pleural effusion, and four reviews on digestive system malignancies, such as hepatocellular carcinoma and pancreatic cancer. Almost all included meta-analyses reported that KLT as adjunctive therapy could improve various efficacy outcomes (such as disease response rates, quality of life, immune indicators) and reduce the rate of occurrence of adverse reactions, such as nausea and vomiting, leukopenia, and anemia. In terms of their methodological quality, three meta-analyses were of low quality, whereas 10 studies were critically low in quality. The methodological flaws main involved items 2 ("predesigned protocol and registration informatio''), 3 ("rationale of study design for inclusion"), 4 ("comprehensive search strategy''), 5 ("literature selection in duplicate''), 7 ("list of excluded studies with reasons''), 8 ("adequate information on included studies''), 10 ("funding support for included primary studies''), and 12 ("evaluation of the potential impact of risk of bias'') based on the AMSTAR 2 tool. Conclusion: Current evidence reveals that KLT is effective and safe as an adjunctive treatment for non-small cell lung cancer, malignant pleural effusion, and digestive system malignancies (such as hepatocellular carcinoma). However, the results assessed in this overview should be further verified using well-designed and clearly reported clinical trials and meta-analyses of KLT.

Treatment and secondary prophylaxis of venous thromboembolism in cancer patients

Cancer-associated thrombosis (CAT) adversely affects the quality of life and survival of people with cancer. A holistic approach is optimal for the treatment and secondary prophylaxis of venous thromboembolism (VTE) including shared decision-making around anticoagulation, considering individual risk factors for VTE recurrence, morbidities from VTE, and resources available in cancer centres around the world. Taking a global perspective on availability and cost, this paper guides the reader through the wider aspects of treatment and secondary thromboprophylaxis which, in turn, influence the recent international guidelines.

Chinese Medicine as an Adjunctive Treatment for Gastric Cancer: Methodological Investigation of meta-Analyses and Evidence Map

Background: Many meta-analyses (MAs) on Chinese medicine (CM) as an adjunctive treatment for gastric cancer have been published in recent years. However, the pooled evidence reported in MAs and their methodological quality remain unknown. Therefore, we designed a study to comprehensively evaluate and summarize the current evidence of CMs for gastric cancer in published MAs.

Methods: A systematic search on MAs published in English from inception to 1st September 2021 was conducted in PubMed and Embase. The AMSTAR-2 tool was used to evaluate the methodological quality of the included MAs, and the results of the quality assessment were visualized using the evidence mapping method. Stata 17/SE was used for statistical analysis (Registration number: INPLASY202190005).

Results: A total of 20 MAs (16 pairwise and 4 network MAs) were included from 118 records. These MAs were published in 14 journals from 2013 to 2021, with the number of patients and trials ranging from 688 to 6,857, and from 10 to 85, respectively. A large number of CMs (e.g., AiDi, FuFangKuShen, and HuaChanSu) in combination with chemotherapy for gastric cancer were identified among the included MAs. According to the pooled results reported in MAs, when compared to chemotherapy alone, CMs in combination with chemotherapy not only improve various outcomes on efficacy (e.g., objective response rate, quality of life) but also reduce various adverse reactions (e.g., leucopenia, nausea and vomiting). Only 2 MAs were low in terms of the overall methodological quality, while the other 18 MAs were all critically low. The methodology was required to be advanced significantly, mainly involving: study protocol and registration, explanation for the inclusion of study design, list of excluded studies with justifications, adequate details of included studies, reporting on funding sources of primary studies, and evaluation of the potential impact of risk of bias. In addition, MAs that received funds support (β = 2.68; 95%CI: 0.40 to 4.96; p = 0.024) or were published in journals with higher impact factor (β = 2.81; 95%CI: 0.69 to 4.92; p = 0.012) had a higher score on the overall methodological quality in the univariate analysis, but the results were not statistically significant according to the multivariate analysis.

Conclusion: Combining CMs with chemotherapy can potentially improve clinical outcomes and reduce the relevant adverse effects in patients with gastric cancer. However, the methodological quality of relevant MAs requires significant improvement, and the current evidence needs to be validated through multinational trials that are well-designed and have a large sample size.

Rivaroxaban vs Dalteparin in Cancer-Associated Thromboembolism: A Randomized Trial

BACKGROUND

Direct oral anticoagulants (DOACs) are an alternative to low-molecular-weight heparin for treating cancer-associated VTE.

RESEARCH QUESTION

Is rivaroxaban as efficient and safe as dalteparin to treat patients with cancer-associated VTE?

STUDY DESIGN AND METHODS

In a randomized open-label noninferiority trial, patients with active cancer who had proximal DVT, pulmonary embolism (PE), or both were assigned randomly to therapeutic doses of rivaroxaban or dalteparin for 3 months. The primary outcome was the cumulative incidence of recurrent VTE, a composite of symptomatic or incidental DVT or PE, and worsening of pulmonary vascular or venous obstruction at 3 months.

RESULTS

Of 158 randomized patients, 74 and 84 patients were assigned to receive rivaroxaban and dalteparin, respectively. Mean age was 69.4 years, and 115 patients (76.2%) had metastatic disease. The primary outcome occurred in 4 and 6 patients in the rivaroxaban and dalteparin groups, respectively (both the intention-to-treat and per-protocol populations: cumulative incidence, 6.4% vs 10.1%; subdistribution hazard ratio [SHR], 0.75; 95% CI, 0.21-2.66). Major bleeding occurred in 1 and 3 patients in the rivaroxaban and dalteparin groups, respectively (cumulative incidence, 1.4% vs 3.7%; SHR, 0.36; 95% CI, 0.04-3.43). Major or clinically relevant nonmajor bleeding occurred in 9 and 8 patients in the rivaroxaban and dalteparin groups, respectively (cumulative incidence, 12.2% vs 9.8%; SHR, 1.27; 95% CI, 0.49-3.26). Overall, 19 patients (25.7%) and 20 patients (23.8%) died in the rivaroxaban and dalteparin groups, respectively (hazard ratio, 1.05; 95% CI, 0.56-1.97).

INTERPRETATION

In this trial comparing rivaroxaban and dalteparin in the treatment of cancer-associated VTE, the number of patients was insufficient to reach the predefined criteria for noninferiority, but efficacy and safety results were consistent with those previously reported with DOACs. An updated meta-analysis of randomized trials comparing DOACs with low-molecular-weight heparin in patients with cancer-associated VTE is provided.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02746185; URL: www.clinicaltrials.gov.