Evaluation of excess statistical significance in meta-analyses of 98 biomarker associations with cancer risk

Effects of probiotics, prebiotics and synbiotics on anthropometric, cardiometabolic and inflammatory markers: An umbrella review of meta-analyses

BACKGROUND & AIMS

Though probiotics, prebiotics and synbiotics have been shown to confer health benefits, their effects on cardiometabolic risk factors remain unclear. Therefore, we conducted an umbrella review to examine their effectiveness on anthropometric, cardiometabolic and inflammatory markers.

METHODS

We conducted an umbrella review on eligible systematic reviews with meta-analysis (SRMA) published from journals' inception till 13 January 2023 retrieved from seven electronic databases (CINAHL, EMBASE, ProQuest, PubMed, Scopus, The Cochrane Library, and Web of Science). Methodological quality was appraised using the Assessment of Multiple Systematic Reviews 2 (AMSTAR2) tool and certainty of evidence was graded into five classes. Random-effects meta-analyses were performed on outcome effect sizes at the SRMA and primary study levels. Extent of overlapping articles were evaluated using corrected cover area.

RESULTS

24 systematic reviews representing 265 unique studies, 1076 unique effect sizes and 25,973 subjects were included. Synbiotics were evidently more effective in improving weight (-1.91 kg, 95%CI -3.45 kg to -0.37 kg, p = 0.02), total cholesterol (-12.17 mg/dl, 95%CI -17.89 mg/dl to -6.46 mg/dl, p < 0.001), low-density lipoprotein (-12.26 mg/dl, 95%CI -18.27 mg/dl to -6.25 mg/dl, p < 0.01), waist circumference (-1.85 cm, 95%CI -2.77 cm to -0.94 cm, p < 0.01), and fasting plasma glucose (-9.68 mg/dl, 95%CI -16.18 mg/dl to -3.18 mg/dl, p < 0.01). Prebiotics were more effective in improving body mass index (-0.34 kg/m2, 95%CI -0.48 kg/m2 to -0.20 kg/m2, p < 0.01), and HOMA-IR (-0.92, 95%CI -1.91 to 0.07, p = 0.06). Probiotics were shown to be more effective in reducing diastolic blood pressure (-1.34 mmHg, 95%CI -2.14 mmHg to -0.55 mmHg, P < 0.01) improving insulin level change (-0.84 mIU/mL, 95%CI -1.27 mIU/mL to -0.41 mIU/mL, p < 0.01), and the percentage of body fat (-0.66%, 95%CI -0.70% to -0.61%, p < 0.01). For all outcomes, the credibility of evidence was classified as class IV.

CONCLUSION

Pre-, pro-, and synbiotics can significantly enhance anthropometric indices, glucose and lipid profiles, blood pressure, and inflammatory markers in individuals confronting obesity. While suggesting their supplementation holds promise for this population, the true clinical impact hinges on tailoring these interventions to specific indications and customizing treatment strategies to align with individual patient needs.

An umbrella review of the evidence associating occupational carcinogens and cancer risk at 19 anatomical sites

Occupational exposure to carcinogens of increasing cancer risk have been extensively suggested. A robust assessment of these evidence is needed to guide public policy and health care. We aimed to classify the strength of evidence for associations of 13 occupational carcinogens (OCs) and risk of cancers. We searched PubMed and Web of Science up to November 2022 to identify potentially relevant studies. We graded the evidence into convincing, highly suggestive, suggestive, weak, or not significant according to a standardized classification based on: random-effects p value, number of cancer cases, 95% confidence interval of largest study, heterogeneity between studies, 95% prediction interval, small study effect, excess significance bias and sensitivity analyses with credibility ceilings. The quality of meta-analysis was evaluated by AMSTAR 2. Forty-eight articles yielded 79 meta-analyses were included in current umbrella review. Evidence of associations were convincing (class I) or highly suggeastive (class II) for asbestos exposure and increasing risk of lung cancer among smokers (RR = 8.79, 95%CI: 5.81-13.25 for cohort studies and OR = 8.68, 95%CI: 5.68-13.24 for case-control studies), asbestos exposure and increasing risk of mesothelioma (RR = 4.61, 95%CI: 2.57-8.26), and formaldehyde exposure and increasing risk of sinonasal cancer (RR = 1.68, 95%CI: 1.38-2.05). Fifteen associations were supported by suggestive evidence (class III). In summary, the current umbrella review found strong associations between: asbestos exposure and increasing risk of lung cancer among smokers; asbestos exposure and increasing risk of mesothelioma; and formaldehyde exposure and higher risk of sinonasal cancer. Other associations might be genuine, but substantial uncertainty remains.

Risk factors for preterm birth: an umbrella review of meta-analyses of observational studies

BACKGROUND

Preterm birth defined as delivery before 37 gestational weeks is a leading cause of neonatal and infant morbidity and mortality. The aim of this study is to summarize the evidence from meta-analyses of observational studies on risk factors associated with PTB, evaluate whether there are indications of biases in this literature, and identify which of the previously reported associations are supported by robust evidence.

METHODS

We searched PubMed and Scopus until February 2021, in order to identify meta-analyses examining associations between risk factors and PTB. For each meta-analysis, we estimated the summary effect size, the 95% confidence interval, the 95% prediction interval, the between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. Evidence was graded as robust, highly suggestive, suggestive, and weak.

RESULTS

Eighty-five eligible meta-analyses were identified, which included 1480 primary studies providing data on 166 associations, covering a wide range of comorbid diseases, obstetric and medical history, drugs, exposure to environmental agents, infections, and vaccines. Ninety-nine (59.3%) associations were significant at P < 0.05, while 41 (24.7%) were significant at P < 10-6. Ninety-one (54.8%) associations had large or very large heterogeneity. Evidence for small-study effects and excess significance bias was found in 37 (22.3%) and 12 (7.2%) associations, respectively. We evaluated all associations according to prespecified criteria. Seven risk factors provided robust evidence: amphetamine exposure, isolated single umbilical artery, maternal personality disorder, sleep-disordered breathing (SDB), prior induced termination of pregnancy with vacuum aspiration (I-TOP with VA), low gestational weight gain (GWG), and interpregnancy interval (IPI) following miscarriage < 6 months.

CONCLUSIONS

The results from the synthesis of observational studies suggest that seven risk factors for PTB are supported by robust evidence. Routine screening for sleep quality and mental health is currently lacking from prenatal visits and should be introduced. This assessment can promote the development and training of prediction models using robust risk factors that could improve risk stratification and guide cost-effective preventive strategies.

TRIAL REGISTRATION

PROSPERO 2021 CRD42021227296.

Risk factors for preterm labor: An Umbrella Review of meta-analyses of observational studies

Preterm birth defined as delivery before 37 gestational weeks, is a leading cause of neonatal and infant morbidity and mortality. Understanding its multifactorial nature may improve prediction, prevention and the clinical management. We performed an umbrella review to summarize the evidence from meta-analyses of observational studies on risks factors associated with PTB, evaluate whether there are indications of biases in this literature and identify which of the previously reported associations are supported by robust evidence. We included 1511 primary studies providing data on 170 associations, covering a wide range of comorbid diseases, obstetric and medical history, drugs, exposure to environmental agents, infections and vaccines. Only seven risk factors provided robust evidence. The results from synthesis of observational studies suggests that sleep quality and mental health, risk factors with robust evidence should be routinely screened in clinical practice, should be tested in large randomized trial. Identification of risk factors with robust evidence will promote the development and training of prediction models that could improve public health, in a way that offers new perspectives in health professionals.

Risk of Dementia in Cancer Survivors: A Meta-Analysis of Population-Based Cohort Studies

Background: A negative association between cancer and Alzheimer’s disease (AD) was revealed. Objective: We aimed to further explore the dementia risk among cancer survivors and then among cancer survivors who received cancer treatment in subsequent subgroup analyses. Methods: Databases of PubMed, Embase, and Cochrane Library were systematically searched from inception to April 1, 2021, following PRISMA and MOOSE guidelines. Relative risks (RR) of dementia were pooled by a random-effects model stratifying the data by potential confounding factors to explore the heterogeneity. This study is registered with PROSPERO, number CRD42021250654. Results: A total of 36 studies were included in this meta-analysis, of which 16 studies were about the risk of dementia in cancer survivors, and 20 studies were about the risk of dementia in survivors who accepted cancer treatment. The pooled RR reached 0.89 ([95% CI = 0.82–0.97], I2 = 97.9%) for dementia and 0.89 ([0.83–0.95], I2 = 92.6%) for AD in cancer survivors compared with non-cancer controls. Notably, both dementia risk and AD risk significantly decreased in survivors of colon, leukemia, small intestine, and thyroid cancers (RR ranged from 0.64 to 0.92). Furthermore, prostate cancer patients treated with androgen deprivation therapy exhibited a significantly increased risk of dementia (RR:1.18 [1.09–1.27], I2 = 89.5%) and AD (RR:1.17 [1.08–1.25], I2 = 81.3%), with evidence of between-study heterogeneity. Conclusion: Currently, available evidence suggests that the risk of dementia among cancer survivors is decreased. However, large-scale prospective cohort studies are warranted to further prove the association.

Homelessness and health-related outcomes: an umbrella review of observational studies and randomized controlled trials

BACKGROUND

Homelessness has been associated with multiple detrimental health outcomes across observational studies. However, relatively few randomized controlled trials (RCTs) have been conducted on people who experience homelessness (PEH). Thus, this umbrella review ranked the credibility of evidence derived from systematic reviews (SRs) and meta-analyses (MAs) of observational studies investigating the associations between homelessness and any health outcome as well as RCTs targeting health needs in this population.

METHODS

Several databases were systematically searched from inception through April 28, 2021. Any SR and/or MA reporting quantitative data and providing a control group were eligible for inclusion. The credibility of the evidence derived from observational studies was appraised by considering the significance level of the association and the largest study, the degree of heterogeneity, the presence of small-study effects as well as excess significance bias. The credibility of evidence was then ranked in five classes. For SRs and/or MAs of RCTs, we considered the level of significance and whether the prediction interval crossed the null. The AMSTAR-2 and AMSTAR-plus instruments were adopted to further assess the methodological quality of SRs and/or MAs. The Newcastle-Ottawa Scale (NOS) was employed to further appraise the methodological quality of prospective cohort studies only; a sensitivity analysis limited to higher quality studies was conducted.

RESULTS

Out of 1549 references, 8 MAs and 2 SRs were included. Among those considering observational studies, 23 unique associations were appraised. Twelve of them were statistically significant at the p≤0.005 level. Included cases had worst health-related outcomes than controls, but only two associations reached a priori-defined criteria for convincing (class I) evidence namely hospitalization due to any cause among PEH diagnosed with HIV infection, and the occurrence of falls within the past year among PEH. According to the AMSTAR-2 instrument, the methodological quality of all included SRs and/or MAs was "critically low." Interventional studies were scant.

CONCLUSION

While homelessness has been repeatedly associated with detrimental health outcomes, only two associations met the criteria for convincing evidence. Furthermore, few RCTs were appraised by SRs and/or MAs. Our umbrella review also highlights the need to standardize definitions of homelessness to be incorporated by forthcoming studies to improve the external validity of the findings in this vulnerable population.

Modifiable predictive factors and all-cause mortality in the non-hospitalized elderly population: An umbrella review of meta-analyses

OBJECTIVE

This umbrella review aimed to summarize the association between modifiable predictive factors and all-cause mortality in the non-hospitalized elderly population, and estimated the credibility and strength of the current evidence.

METHODS

PubMed, Embase, Web of science, and EBSCOhost were searched up to February 28, 2022. Random-effect summary effect sizes and 95% confidence intervals (CIs), heterogeneity, small-study effect, excess significance bias, as well as 95% prediction intervals (PIs) were calculated. Methodological quality was assessed with the Assessment of Multiple Systematic Reviews 2 (AMSTAR-2) tool. The credibility of the included meta-analyses was graded from convincing to weak using established criteria. This umbrella review was registered with PROSPERO, CRD 42021282183.

RESULTS

In total, 32 predictive factors involving 49 associations extracted from 35 meta-analyses were analyzed. Forty-three of the 49 (87.8%) associations presented nominal significant effects by the random-effect model (P < 0.05), of which 34 had harmful associations and nine had beneficial associations with all-cause mortality. Frailty (FRAIL scale), low short physical performance battery (SPPB) score, and fewer daily steps carried a more than three-fold risk for all-cause mortality. Convincing evidence showed that weight fluctuation, prefrailty and frailty status, sarcopenia, low SPPB score, fewer daily steps, and fatigue increased the risk of all-cause mortality, while daily moderate-to-vigorous physical activity (MVPA) duration and total physical activity participation reduced the risk of death. There were twenty, nine, five, and six associations that yielded highly suggestive, suggestive, weak, and non-significant grades of evidence. Thirty-four (69.4%) of the associations exhibited significant heterogeneity. Twenty-two associations presented 95% PIs excluding the null value, two indicated small-study effects, and three had evidence for excess significance bias, respectively. The methodological quality of most meta-analyses was rated as low (37.1%) or critically low (42.9%).

CONCLUSIONS

A summary of the currently available meta-analyses suggests that a broad range of modifiable predictive factors are significantly associated with all-cause mortality risk in the non-hospitalized elderly population. The most credible evidence indicates that physical function represented by frailty and sarcopenia, as well as physical activity, are significant predictors for all-cause mortality. This umbrella review may provide prognostic information to direct appropriate diagnostic evaluation and treatment goals in the future. More solid evidence is still needed coming from moderate-to-high quality meta-analyses.

Long-term PM2.5 exposure and various health outcomes: An umbrella review of systematic reviews and meta-analyses of observational studies

Adverse effects from exposure to particulate matter <2.5 μm in diameter (PM_2.5) on health-related outcomes have been found in a range of experimental and epidemiological studies. This study aimed to assess the significance, validity, and reliability of the relationship between long-term PM_2.5 exposure and various health outcomes. The Embase, PubMed, Web of Science, CNKI, WANFANG, VIP, and SinoMed databases and reference lists of the retrieved review articles were searched to obtain meta-analysis and systematic reviews focusing on PM_2.5-related outcomes as of August 31, 2021. Random-/fixed-effects models were applied to estimate summary effect size and 95% confidence intervals (CIs). The quality of included meta-analyses was evaluated based on the AMSTAR 2 tool. Small-study effect and excess significance bias studies were conducted to further assess the associations. Registered PROSPERO number: CRD42020200606. This included 24 articles involving 71 associations between PM_2.5 exposure and the health outcomes. The evidence for the positive association of 10 μg/m³ increments of long-term exposure to PM_2.5 and stroke incidence in Europe was convincing (effect size = 1.07, 95% CI: 1.05-1.10). There was evidence that was highly suggestive of a positive association between 10 μg/m³ increments of long-term exposure to PM_2.5 and the following health-related outcomes: mortality of lung cancer (effect size = 1.11, 95% CI: 1.08-1.13) and Alzheimer's disease (effect size = 4.79, 95% CI: 2.79-8.21). There was highly suggestive evidence that chronic obstructive pulmonary disease risk is positively associated with higher long-term PM_2.5 exposure versus lower long-term PM_2.5 exposure (effect size = 2.32, 95% CI: 1.88-2.86). In conclusion, the positive association of long-term exposure to PM_2.5 and stroke incidence in Europe was convincing. Given the validity of numerous associations of long-term exposure to PM_2.5 and health-related outcomes is subject to biases, more robust evidence is urgently needed.

Neurological, Psychiatric, and Psychological Implications of the COVID-19 Pandemic: Protocol for a Large-Scale Umbrella Review of Observational Studies

The severe acute respiratory syndrome coronavirus 2 disease (SARS-CoV-2) is the most severe manifestation of the coronavirus disease 2019 (COVID-19) pandemic. Accruing evidence indicates that the COVID-19 pandemic may have profound deleterious neurological, psychiatric, and psychological outcomes. The number of systematic reviews (SRs) and meta-analyses (MAs) on this topic has grown exponentially. This protocol aims to synthesize all evidence from SRs and MAs on the associations between the COVID-19 pandemic and neuropsychiatric outcomes. The following electronic databases will be systematically searched from inception up to 15 January 2022: PubMed, Embase, APA PsycINFO, and Cochrane Reviews. An umbrella review (UR) of SRs and MAs of observational studies will be conducted. SRs and/or MAs of observational studies examining any direct or indirect association of COVID-19 with the neuropsychiatric outcomes will be deemed eligible for potential inclusion in this UR. The direct associations include the impact on the (1) prognosis of COVID-19 and (2) neuropsychiatric sequelae after COVID-19 infection. The indirect associations include the influence of the COVID-19 pandemic on the (1) treatments and (2) outcomes of neurological and psychiatric conditions associated with the COVID-19 pandemic.

Efficacy and Safety of Non-Operative Management of Uncomplicated Acute Appendicitis Compared to Appendectomy: An Umbrella Review of Systematic Reviews and Meta-Analyses

BACKGROUND

Non-operative management (NOM) of uncomplicated acute appendicitis (AA) has been introduced as an alternative to appendectomy. This umbrella review aimed to provide an overview of the efficacy and safety of NOM of uncomplicated AA in the published systematic reviews.

METHODS

This umbrella review has been reported in line with the PRISMA guidelines and umbrella review approach. Systematic reviews with and without meta-analyses on the efficacy of NOM of AA were analyzed. The quality of the reviews was assessed with the AMSTAR 2 tool. The main outcomes measures were the treatment failure and complication rates of NOM and hospital stay as compared to appendectomy.

RESULTS

Eighteen systematic reviews were included to this umbrella review. Eight reviews documented higher odds of failure with NOM, whereas two reviews revealed similar odds of failure. Six reviews reported lower odds of complications with NOM, six reported similar odds, and one reported lower odds of complications with surgery. Eight reviews reported similar hospital stay between NOM and appendectomy, one reported longer stay with NOM and another reported shorter stay with NOM. Pooled analyses showed that NOM was associated with higher treatment failure overall, in children-only, adults only, and RCTs-only meta-analyses. NOM was associated with lower complications overall, yet children-only and RCTs-only analyses revealed similar complications to surgery. NOM was associated with shorter stay in the overall and adult-only analysis, but not in the children-only analysis.

CONCLUSIONS

NOM of AA is associated with higher treatment failure, marginally lower rate of complications and shorter stay than appendectomy.

Umbrella Reviews: What They Are and Why We Need Them

Evidence in clinical research is accumulating and scientific publications have increased exponentially in the last decade across all disciplines. Available information should be critically assessed. Here, we focus on umbrella reviews, an approach that systematically collects and evaluates information from multiple systematic reviews and meta-analyses. To facilitate the design and the conduct of such a study, we provide a step-by-step guide on how to perform an umbrella review. We also present ways to report the summary findings, we describe various proposed grading criteria, and we discuss potential limitations.

Environmental Risk Factors for Endometriosis: An Umbrella Review of a Meta-Analysis of 354 Observational Studies With Over 5 Million Populations

Background: The association between a diverse array of environmental risk factors and the risk of endometriosis is contradictory. Objective: To summarize the evidence of associations between environmental risk factors and the risk of endometriosis. Methods: Databases such as PubMed, EMBASE, Web of Science, and ClinicalTrial.gov were systematically searched in June 2020. Meta-analyses of observational studies investigated any environmental exposure (non-genetic) and endometriosis risk. For each article, we estimated the summary effect size, 95% CIs, and the 95% prediction interval (PI). We also estimated the between-study heterogeneity expressed by I ², evidence for small-study effects, and evidence of excess significance bias. Results: About 12 eligible articles (featuring 143,422 cases and 5,112,967 participants) yielded data on 40 unique environmental risk factors, including life styles (n = 16), reproductive factors (n = 3), early life factors (n = 4), and a range of other risk factors [e.g., phthalate metabolites, endocrine-disrupting chemicals, and body mass index (BMI)]. About 25 of these 40 associations (62.5%) were statistically significant (p < 0.05) under random-effects models. Evidence for an association was indicated for alcohol intake [relative risk (RR): 1.25; 95% CI: 1.11-1.41] and the exposure to endocrine disruptor chemicals (EDCs) (RR: 1.41; 95% CI: 1.23-1.60) while 15 associations presented only weak evidence. Conclusions: Our analyses showed that alcohol intake and exposure to endocrine-disrupting chemicals may be potential risk factors for endometriosis and supported by suggestive epidemiological evidence. However, it was evident that there was substantial heterogeneity and/or bias between the different studies featured in various meta-analyses included in this review; therefore, the outcomes of our analysis should be interpreted cautiously.

Associations of Nutritional, Lifestyle, and Metabolic Factors With Non-alcoholic Fatty Liver Disease: An Umbrella Review With More Than 380,000 Participants

Background & Aims: Nonalcoholic fatty liver disease (NAFLD) is the most common liver injury. We performed this umbrella review of meta-analyses to summarize the evidence on the associations of nutritional, lifestyle, and metabolic factors with NAFLD.

Methods: We searched the PubMed, Embase, and Web of Science databases from inception until July 2, 2020, to identify meta-analyses of observational studies which explored the associations of nutritional, lifestyle, and metabolic factors with NAFLD. Evidence levels were assessed using summary effect sizes, 95% prediction intervals, between-study heterogeneity, evidence of small-study effects, and evidence of excess significance bias for each meta-analysis. (No. of PROSPERO, CRD42020200124).

Results: Twenty two risk or protective factors from 10 published meta-analyses were included and studied. Three risk factors (sugar-sweetened beverage consumption, serum fetuin-A, and waist circumference) with highly suggestive levels of evidence and three risk factors (soft drink consumption, former smoking, and body mass index) with suggestive levels of evidence were identified. Only two protective factors (physical activity and serum vitamin D level [among adults in Western countries]) with suggestive levels of evidence were identified. Furthermore, other six risk factors and two protective factors with weak levels of evidence were identified.

Conclusions: We found varying levels of evidence of associations of nutritional, lifestyle, and metabolic factors and NAFLD. The results suggest that nutritional and lifestyle management should be considered as a major primary preventive strategy for NAFLD. Moreover, considering the low quality of included meta-analyses and limited area of research topics, future high-quality original studies and meta-analyses should be performed to study these associations.

Therapeutic interventions for childhood cancer: An umbrella review of randomized evidence

Treatment advancements in pediatric cancer have improved prognosis, but the strength of supporting evidence has not been thoroughly evaluated. To critically appraise it, we performed an umbrella review of meta-analyses of randomized controlled trials examining the efficacy and safety of therapeutic interventions for pediatric malignancies. Fourteen publications (68 meta-analyses, 31,496 participants) were eligible. Acute lymphoblastic leukemia (ALL) was investigated at most. Substantial heterogeneity was detected in 10 associations, with limited indications for small-study effects and excess-significance bias. The most concrete evidence pertained to the use of methotrexate and vincristine-prednisone pulses for ALL, improving event-free survival. Evidence regarding other cancers was relatively weak. Conclusively, we found few small meta-analyses focusing mainly on ALL. Randomized evidence stemming from adult populations still seems to serve as valuable indirect evidence backup. More randomized evidence and individual patient data meta-analyses are needed to increase certainty and precision in the care of pediatric cancer patients.

Type 2 Diabetes and Cancer: An Umbrella Review of Observational and Mendelian Randomization Studies

BACKGROUND

Type 2 diabetes mellitus (T2DM) has been associated with an increased risk of developing several common cancers, but it is unclear whether this association is causal. We aimed to summarize the evidence on T2DM and cancer and evaluate the validity of associations from both observational and Mendelian randomization (MR) studies.

METHODS

We performed an umbrella review of the evidence across meta-analyses of observational studies that examined associations of T2DM with risk of developing or dying from site-specific cancers, and MR studies that explored the potential causal association of T2DM and associated biomarkers with cancer risk.

RESULTS

We identified eligible observational meta-analyses that assessed associations between T2DM and cancer incidence for 18 cancer sites, cancer mortality for seven sites, and cancer incidence or mortality for four sites. Positive associations between T2DM and six cancers reached strong or highly suggestive evidence. We found eight MR studies assessing the association of genetically predicted T2DM and seven and eight studies assessing the association of genetically predicted fasting insulin or fasting glucose concentrations, respectively, upon site-specific cancers. Positive associations were found between genetically predicted T2DM and fasting insulin and risk of six cancers. There was no association between genetically predicted fasting plasma glucose and cancer except for squamous cell lung carcinoma.

CONCLUSIONS

We found robust observational evidence for the association between T2DM and colorectal, hepatocellular, gallbladder, breast, endometrial, and pancreatic cancers.

IMPACT

Potential causal associations were identified for genetically predicted T2DM and fasting insulin concentrations and risk of endometrial, pancreas, kidney, breast, lung, and cervical cancers.

Robotic versus laparoscopic gastrectomy for gastric cancer: an umbrella review of systematic reviews and meta-analyses

An umbrella review was performed to summarize literature data and to investigate benefits and harm of robotic gastrectomy (RG) compared to laparoscopic (LG) approach. To overcome the intrinsic limitations of laparoscopy, the robotic approach is claimed to facilitate lymph-node dissection and complex reconstruction after gastrectomy, to assure oncologic safety also in advanced gastric cancer. A literature search was conducted in PubMed, Cochrane and Embase databases for all meta-analyses published up to December 2019. The search strategy was previously published in a protocol. We selected fourteen meta-analyses comparing outcomes between LG and RG with curative intent in patients with diagnosis of resectable gastric cancer. We highlight that RG has a longer operation time, inferior blood loss, reduction in hospital stay and a more rapid recovery of bowel function. In meta-analyses with statistical significance the number of nodes removed in RG is higher than LG and the distal margin of resection is higher. There is no difference in terms of total complication rate, mortality, morbidity, anastomotic leakage, anastomotic stenosis, intestinal obstruction and in conversion rate to open technique. The safety and efficacy of robotic gastrectomy are not clearly supported by strong evidence, suggesting that the outcomes reported for each surgical technique need to be interpreted with caution, in particular for the meta-analyses in which the heterogeneity is large. Certainly, robotic gastrectomy is associated with shorter time to oral intake, lesser intraoperative bleeding and longer operation time with an acceptable level of evidence. On the other hand, the data regarding other outcomes are insufficient as well as non-significant, from an evidence point of view, to draw any robust conclusion.

Environmental Risk Factors and Congenital Heart Disease: An Umbrella Review of 165 Systematic Reviews and Meta-Analyses With More Than 120 Million Participants

Background: The etiology of congenital heart disease (CHD) has been extensively studied in the past decades. Therefore, it is critical to clarify clear hierarchies of evidence between types of environmental factors and CHD. Methods: Electronic searches in PubMed, Embase, Web of Science, Cochrane database were conducted from inception to April 20, 2020 for meta-analyses investigating the aforementioned topic. Results: Overall, 41 studies including a total of 165 meta-analyses of different environmental factors and CHD were examined, covering a wide range of risk factors. The summary random effects estimates were significant at P < 0.05 in 63 meta-analyses (38%), and 15 associations (9%) were significant at P < 10^-6. Of these meta-analyses, eventually one risk factor (severe obesity; relative risk: 1.38, 95% confidence interval: 1.30-1.47) had significant summary associations at P < 10^-6, included more than 1,000 cases, had 95% prediction intervals excluding the null value, and were not suggestive of large heterogeneity (I ² < 50%), small-study effects (P-value for Egger's test > 0.10), or excess significance (P > 0.10). Eight associations (5%) (including maternal lithium exposure, maternal obesity, maternal alcohol consumption, and maternal fever) had results that were significant at P < 10^-6, included more than 1,000 cases, and had 95% prediction intervals excluding the null value (highly suggestive). Conclusion: This umbrella review shows that many environmental factors have substantial evidence in relation to the risk of developing CHD. More and better-designed studies are needed to establish robust evidence between environmental factors and CHD. Systematic Review Registration: [PROSPERO], identifier [CRD42020193381].

The prognostic value of late gadolinium enhancement in heart diseases: an umbrella review of meta-analyses of observational studies

OBJECTIVES

Cardiac magnetic resonance imaging (CMR) has proven itself as an accurate and robust diagnostic approach and has been widely used in the detection of various heart diseases. An increasing number of studies focusing more on the prognostic aspect of LGE-CMR arose in recent years, contributing to the redundant systematic reviews and meta-analyses in this field. By providing a bird's eye view and performing scrupulous evidence rating, this umbrella review aims to help clinical practitioners and policy-makers interpret the results of the meta-analyses on the prognostic role of late gadolinium enhancement (LGE) in patients with heart diseases.

METHODS

An umbrella review of meta-analyses of observational studies.

RESULTS

The 11 included systematic reviews comprise 33 meta-analyses covering 11 types of heart diseases, 19 different outcomes, 23,058 subjects, and 5393 events. Thirty-one of 33 meta-analyses were found supported by weak pieces of evidence and the remaining were deemed not suggestive. The meta-analysis with a p value of 9.21 × 10^-15 and 991 events was updated by strictly re-conducting the meta-analysis by Becker et al. The updated meta-analysis on the prognostic role of LGE in subjects with non-ischemic dilated cardiomyopathy (DCM) in terms of major adverse cardiovascular events (MACE) included 1131 events and was rated as highly suggestive evidence.

CONCLUSIONS

The prognostic role of LGE in DCM patients in terms of MACE is supported by highly suggestive evidence, which may facilitate the optimization of the timing of prophylactic implantable or wearable implantable cardioverter-defibrillators (ICD) considering the high risk of MACE and lower expectation of recovery.

KEY POINTS

• Cardiac magnetic resonance imaging (CMR) has been widely used in the detection of various heart diseases. Numerous studies focusing on the prognostic aspect of LGE arose in recent years. • The meta-analysis on the prognostic role of LGE in dilated cardiomyopathy (DCM) patients in terms of major adverse cardiovascular events (MACE) by Becker et al was updated and was deemed to be supported by highly suggestive evidence. • The credibility of the meta-analysis supported by highly suggestive evidence may facilitate the optimization of the timing of prophylactic implantable or wearable implantable cardioverter defibrillators (ICD) considering the high risk of MACE and lower expectation of recovery.

Neutrophil to lymphocyte ratio and cancer prognosis: an umbrella review of systematic reviews and meta-analyses of observational studies

BACKGROUND

Although neutrophils have been linked to the progression of cancer, uncertainty exists around their association with cancer outcomes, depending on the site, outcome and treatments considered. We aimed to evaluate the strength and validity of evidence on the association between either the neutrophil to lymphocyte ratio (NLR) or tumour-associated neutrophils (TAN) and cancer prognosis.

METHODS

We searched MEDLINE, Embase and Cochrane Database of Systematic Reviews from inception to 29 May 2020 for systematic reviews and meta-analyses of observational studies on neutrophil counts (here NLR or TAN) and specific cancer outcomes related to disease progression or survival. The available evidence was graded as strong, highly suggestive, suggestive, weak or uncertain through the application of pre-set GRADE criteria.

RESULTS

A total of 204 meta-analyses from 86 studies investigating the association between either NLR or TAN and cancer outcomes met the criteria for inclusion. All but one meta-analyses found a hazard ratio (HR) which increased risk (HR > 1). We did not find sufficient meta-analyses to evaluate TAN and cancer outcomes (N = 9). When assessed for magnitude of effect, significance and bias related to heterogeneity and small study effects, 18 (9%) associations between NLR and outcomes in composite cancer endpoints (combined analysis), cancers treated with immunotherapy and some site specific cancers (urinary, nasopharyngeal, gastric, breast, endometrial, soft tissue sarcoma and hepatocellular cancers) were supported by strong evidence.

CONCLUSION

In total, 60 (29%) meta-analyses presented strong or highly suggestive evidence. Although the NLR and TAN hold clinical promise in their association with poor cancer prognosis, further research is required to provide robust evidence, assess causality and test clinical utility.

TRIAL REGISTRATION

PROSPERO CRD42017069131 .

Vitamin D and Clinical Cancer Outcomes: A Review of Meta-Analyses

The relationship between vitamin D status or supplementation and cancer outcomes has been examined in several meta‐analyses. To address remaining knowledge gaps, we conducted a systematic overview and critical appraisal of pertinent meta‐analyses. For meta‐analyses of trials, we assessed their quality using AMSTAR‐2 (A Measurement Tool to Assess Systematic Reviews), strength of associations using umbrella review methodology and credibility of evidence using GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) criteria. Meta‐analyses of observational studies reported inverse associations of 25OHD with risk of cancer incidence and cancer mortality and, particularly for colorectal cancer, fulfilled some of Bradford‐Hill's causation criteria. In meta‐analyses of trials, vitamin D supplementation did not affect cancer incidence. However, we found credible evidence that vitamin D supplementation reduced total cancer mortality risk, with five out of six meta‐analyses reporting a relative risk (RR) reduction of up to 16%: RR, 0.84 (95% CI, 0.74–0.95). The strength of the association, however, was classified as weak. This was true among meta‐analyses of high, moderate, and lower quality (AMSTAR‐2–rated). Trials did not include large numbers of vitamin D‐deficient participants; many tested relatively low doses and lacked sufficiently powered data on site‐specific cancers. In conclusion, meta‐analyses show that, although observational evidence indicates that low vitamin D status is associated with a higher risk of cancer outcomes, randomized trials show that vitamin D supplementation reduces total cancer mortality, but not cancer incidence. However, trials with larger proportions of vitamin D‐insufficient participants and longer durations of follow‐up, plus adequately powered data on site‐specific common cancers, would provide further insight into the evidence base. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Non-genetic biomarkers and colorectal cancer risk: Umbrella review and evidence triangulation

Several associations between non-genetic biomarkers and colorectal cancer (CRC) risk have been detected, but the strength of evidence and the direction of associations are not confirmed. We aimed to evaluate the evidence of these associations and integrate results from different approaches to assess causal inference. We searched Medline and Embase for meta-analyses of observational studies, meta-analyses of randomized clinical trials (RCTs), and Mendelian randomization (MR) studies measuring the associations between non-genetic biomarkers and CRC risk and meta-analyses of RCTs on supplementary micronutrients. We repeated the meta-analyses using random-effects models and categorized the evidence based on predefined criteria. We described each MR study and evaluated their credibility. Seventy-two meta-analyses of observational studies and 18 MR studies on non-genetic biomarkers and six meta-analyses of RCTs on micronutrient intake and CRC risk considering 65, 42, and five unique associations, respectively, were identified. No meta-analyses of RCTs on blood level biomarkers have been found. None of the associations were classified as convincing or highly suggestive, three were classified as suggestive, and 26 were classified as weak. For three biomarkers explored in MR studies, there was evidence of causality and seven were classified as likely noncausal. For the first time, results from both observational and MR studies were integrated by triangulating the evidence for a wide variety of non-genetic biomarkers and CRC risk. At blood level, lower vitamin D, higher homeostatic model assessment-insulin resistance, and human papillomavirus infection were associated with higher CRC risk while increased linoleic acid and oleic acid and decreased arachidonic acid were likely causally associated with lower CRC risk. No association was found convincing in both study types.

Use of antidepressants during pregnancy and neonatal outcomes: An umbrella review of meta-analyses of observational studies

BACKGROUND

Pregnant women who suffer from depressive disorders are likely to be treated with antidepressant (AD) medications. Recent meta-analyses underlined the possible relation between AD use and several neonatal outcomes, although the underlying mechanisms remains unclear.

METHODS

To summarise and evaluate the associations between AD use in pregnancy and neonatal outcomes, we conducted an umbrella review of meta-analyses of observational studies published up to December 2019 in PubMed and Embase. Summary risk estimates for the associations between use of AD as a whole, or specific AD classes and drugs, and the risk of neonatal outcomes were reported.

RESULTS

Our review included 22 meta-analyses investigating 69 associations. However, none were supported by convincing evidence. Highly suggestive evidence regarded the associations between (i) any time AD exposure and the risk of preterm birth (relative risk, 1.68; 95% confidence interval 1.52, 1.86), (ii) any time exposure to selective serotonin reuptake inhibitors (SSRIs) and the risk of preterm birth (1.43; 1.22, 1.37) and (iii) respiratory distress (1.33; 1.14, 1.55), and (iv) SSRI exposure during the first trimester of pregnancy and the risk of cardiovascular malformations (1.25; 1.13, 1.39). Suggestive evidence was obtained for any time AD exposure on 1-min low Apgar score (absolute average difference, -0.34; -0.53, -0.14).

CONCLUSIONS

Overall, the effects of AD exposure during pregnancy on neonatal outcomes have been extensively studied, but few of the associations are graded as high quality evidence. More prospective studies and large collaborations with comprehensive standardised reporting of analyses are needed.

Aspirin and Its Potential Preventive Role in Cancer: An Umbrella Review

Background: Aspirin is one of the most commonly prescribed drugs worldwide and has been reported to possess anti-cancer properties in addition to antipyretic and analgesic effects. This umbrella review summarizes systematic reviews and meta-analyses that investigate the association between aspirin and cancer risk, aiming to help clinical and public health decision-makers interpret the results of these studies when re-positioning aspirin. Methods: An umbrella review of systematic reviews and meta-analyses. Results: The associations that reached statistical significance (17 in total) indicated potential preventive effects of aspirin on certain cancers or precancerous lesions. We found that no association was supported by strong evidence. Only one association (aspirin and overall cancer risk) was supported by highly suggestive evidence. The evidence supporting the association between aspirin and the risk of breast cancer, non-cardia gastric cancer, or prostate cancer was considered to be highly suggestive. The remaining 23 associations were supported by weak (13) or not suggestive evidence (10). Conclusions: The association between aspirin and a reduced risk of esophageal squamous cell carcinoma is supported by strong evidence, researchers and policy makers should pay more attention to the potential merit of repositioning aspirin to prevent esophageal squamous cell carcinoma.

Understanding of researcher behavior is required to improve data reliability

BACKGROUND

A lack of data reproducibility ("reproducibility crisis") has been extensively debated across many academic disciplines.

RESULTS

Although a reproducibility crisis is widely perceived, conclusive data on the scale of the problem and the underlying reasons are largely lacking. The debate is primarily focused on methodological issues. However, examples such as the use of misidentified cell lines illustrate that the availability of reliable methods does not guarantee good practice. Moreover, research is often characterized by a lack of established methods. Despite the crucial importance of researcher conduct, research and conclusive data on the determinants of researcher behavior are widely missing.

CONCLUSION

Meta-research that establishes an understanding of the factors that determine researcher behavior is urgently needed. This knowledge can then be used to implement and iteratively improve measures that incentivize researchers to apply the highest standards, resulting in high-quality data.

Risk factors for gestational diabetes: An umbrella review of meta-analyses of observational studies

BACKGROUND/OBJECTIVE

Gestational diabetes mellitus (GDM) is a common pregnancy complication, with complex disease mechanisms, and several risk factors may contribute to its onset. We performed an umbrella review to summarize the evidence from meta-analyses of observational studies on risk factors associated with GDM, evaluate whether there are indications of biases in this literature and identify which of the previously reported associations are supported by convincing evidence.

METHODS

We searched PubMed and ISI Web of Science from inception to December 2018 to identify meta-analyses examining associations between putative risk factors for GDM. For each meta-analysis we estimated the summary effect size, the 95% confidence interval, the 95% prediction interval, the between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias.

RESULTS

Thirty eligible meta-analyses were identified, providing data on 61 associations. Fifty (82%) associations had nominally statistically significant findings (P<0.05), while only 15 (25%) were significant at P<10-6 under the random-effects model. Only four risk factors presented convincing evidence:, low vs. normal BMI (cohort studies), BMI ~30-35 kg/m2 vs. normal BMI, BMI >35 kg/m2 vs. normal BMI, and hypothyroidism.

CONCLUSIONS

The compilation of results from synthesis of observational studies suggests that increased BMI and hypothyroidism show the strongest consistent evidence for an association with GDM. Diet and lifestyle modifications in pregnancy should be tested in large randomized trials. Our findings suggest that women with known thyroid disease may be offered screening for GDM earlier in pregnancy.

Examining reproducibility in psychology: A hybrid method for combining a statistically significant original study and a replication

The unrealistically high rate of positive results within psychology has increased the attention to replication research. However, researchers who conduct a replication and want to statistically combine the results of their replication with a statistically significant original study encounter problems when using traditional meta-analysis techniques. The original study's effect size is most probably overestimated because it is statistically significant, and this bias is not taken into consideration in traditional meta-analysis. We have developed a hybrid method that does take the statistical significance of an original study into account and enables (a) accurate effect size estimation, (b) estimation of a confidence interval, and (c) testing of the null hypothesis of no effect. We analytically approximate the performance of the hybrid method and describe its statistical properties. By applying the hybrid method to data from the Reproducibility Project: Psychology (Open Science Collaboration, 2015), we demonstrate that the conclusions based on the hybrid method are often in line with those of the replication, suggesting that many published psychological studies have smaller effect sizes than those reported in the original study, and that some effects may even be absent. We offer hands-on guidelines for how to statistically combine an original study and replication, and have developed a Web-based application ( https://rvanaert.shinyapps.io/hybrid ) for applying the hybrid method.

Systemic Metabolism, Its Regulators, and Cancer: Past Mistakes and Future Potential

There has been a resurgence of interest in cancer metabolism; primarily in the resetting of metabolism within malignant cells. Metabolism within cells has always been a tightly regulated process; initially in protozoans due to metabolic enzymes, and the intracellular signaling pathways that regulate these, being directly sensitive to the availability of nutrients. With the evolution of metazoans many of these controls had been overlaid by extra-cellular regulators that ensured coordinated regulation of metabolism within the community of cells that comprised the organism. Central to these systemic regulators is the insulin/insulin-like growth factor (IGF) system that throughout evolution has integrated the control of tissue growth with metabolic status. Oncological interest in the main systemic metabolic regulators greatly subsided when pharmaceutical strategies designed to treat cancers failed in the clinic. During the same period, however the explosion of new information from genetics has revealed the complexity and heterogeneity of advanced cancers and helped explain the problems of managing cancer when it reaches such a stage. Evidence has also accumulated implying that the setting of the internal environment determines whether cancers progress to advanced disease and metabolic status is clearly an important component of this local ecology. We are in the midst of an epidemic of metabolic disorders and there is considerable research into strategies for controlling metabolism. Integrating these new streams of information suggests new possibilities for cancer prevention; both primary and secondary.

When Is Enough, Enough? When Are More Observational Epidemiologic Studies Needed to Resolve a Research Question: Illustrations Using Biomarker-Cancer Associations

BACKGROUND

Research reproducibility is vital for translation of epidemiologic findings. However, repeated studies of the same question may be undertaken without enhancing existing knowledge. To identify settings in which additional research is or is not warranted, we adapted research synthesis metrics to determine number of additional observational studies needed to change the inference from an existing meta-analysis.

METHODS

The fail-safe number (FSN) estimates number of additional studies of average weight and null effect needed to drive a statistically significant meta-analysis to null (P ≥ 0.05). We used conditional power to determine number of additional studies of average weight and equivalent heterogeneity to achieve 80% power in an updated meta-analysis to detect the observed summary estimate as statistically significant. We applied these metrics to a curated set of 98 meta-analyses on biomarkers and cancer risk.

RESULTS

Both metrics were influenced by number of studies, heterogeneity, and summary estimate size in the existing meta-analysis. For the meta-analysis on Helicobacter pylori and gastric cancer with 15 studies [OR = 2.29; 95% confidence interval (CI), 1.71-3.05], FSN was 805 studies, supporting futility of further study. For the meta-analysis on dehydroepiandrosterone sulfate and prostate cancer with 7 studies (OR = 1.29; 95% CI, 0.99-1.69), 5 more studies would be needed for 80% power, suggesting further study could change inferences.

CONCLUSIONS

Along with traditional assessments, these metrics could be used by stakeholders to decide whether additional studies addressing the same question are needed.

IMPACT

Systematic application of these metrics could lead to more judicious use of resources and acceleration from discovery to population-health impact.

Genetic and non-genetic risk factors for pre-eclampsia: umbrella review of systematic reviews and meta-analyses of observational studies

OBJECTIVE

To summarize evidence from the literature on genetic and non-genetic risk factors associated with pre-eclampsia (PE), assess the presence of statistical bias in the studies and identify risk factors for which there is robust evidence supporting their association with PE.

METHODS

PubMed and ISI Web of Science were searched from inception to October 2016, to identify systematic reviews and meta-analyses of observational studies examining associations between genetic or non-genetic risk factors and PE. For each meta-analysis, the summary-effect size was estimated using random-effects and fixed-effects models, along with 95% CIs and the 95% prediction interval. Between-study heterogeneity was expressed using the I² statistic, and evidence of small-study effects (large studies had significantly more conservative results than smaller studies) and evidence of excess significance bias (too many studies with statistically significant results) were estimated.

RESULTS

Fifty-eight eligible meta-analyses were identified, which included 1466 primary studies and provided data on 130 comparisons of risk factors associated with PE, covering a wide range of comorbid diseases, genetic factors, exposure to environmental agents and biomarkers. Sixty-five (50%) associations had nominally statistically significant findings at P < 0.05, while 16 (12%) were significant at P < 10^-6 . Sixty-five (50%) associations had large or very large heterogeneity. Evidence for small-study effects and excess significance bias was found in 10 (8%) and 26 (20%) associations, respectively. The only non-genetic risk factor with convincing evidence for an association with PE was oocyte donation vs spontaneous conception, which had a summary odds ratio of 4.33 (95% CI, 3.11-6.03), was supported by 2712 cases with small heterogeneity (I²  = 26%) and 95% prediction intervals excluding the null value, and without hints of small-study effects (P for Egger's test > 0.10) or excess of significance (P > 0.05). Of the statistically significant (P < 0.05) genetic risk factors for PE, only PAI-1 4G/5G (recessive model) polymorphism was supported by strong evidence for a contribution to the pathogenesis of PE. Eleven factors (serum iron level, pregnancy-associated plasma protein-A, chronic kidney disease, polycystic ovary syndrome, mental stress, bacterial and viral infections, cigarette smoking, oocyte donation vs assisted reproductive technology, obesity vs normal weight, severe obesity vs normal weight and primiparity) presented highly suggestive evidence for an association with PE.

CONCLUSIONS

A large proportion of meta-analyses of genetic and non-genetic risk factors for PE have caveats that threaten their validity. Oocyte donation vs spontaneous conception and PAI-1 4G/5G polymorphism (recessive model) showed the strongest consistent evidence for an association with risk for PE. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Physical activity and cancer: an umbrella review of the literature including 22 major anatomical sites and 770 000 cancer cases

OBJECTIVE

To provide an overview of the breadth and validity of claimed associations between physical activity and risk of developing or dying from cancer.

DESIGN

Umbrella review.

DATA SOURCES

We searched Medline, Embase, Cochrane Database and Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Systematic reviews about physical activity and cancer incidence and cancer mortality in different body sites among general population.

RESULTS

We included 19 reviews covering 22 cancer sites, 26 exposure-outcome pairs meta-analyses and 541 original studies. Physical activity was associated with lower risk of seven cancer sites (colon, breast, endometrial, lung, oesophageal, pancreas and meningioma). Only colon (a protective association with recreational physical activity) and breast cancer (a protective association with overall physical activity) were supported by strong evidence and highly suggestive evidence, respectively. Evidence from endometrial, lung, oesophageal, pancreas and meningioma presented hints of uncertainty and bias in the literature (eg, not reaching P values<10^-6) showing large between-study heterogeneity and/or not demonstrating a definite direction for the effect when 95% prediction intervals were considered. Four of the 26 meta-analyses showed small study effects and 4 showed excess significance.

CONCLUSION

Physical activity is associated with a lower risk of several cancers, but only colon and breast cancer associations were supported by strong or highly suggestive evidence, respectively. Evidence from other cancer sites was less consistent, presenting hints of uncertainty and/or bias.

Does psychotherapy work? An umbrella review of meta-analyses of randomized controlled trials

OBJECTIVE

To map and evaluate the evidence across meta-analyses of randomized controlled trials (RCTs) of psychotherapies for various outcomes.

METHODS

We identified 173 eligible studies, including 247 meta-analyses that synthesized data from 5157 RCTs via a systematic search from inception to December 2016 in the PubMed, PsycINFO and Cochrane Database of Systematic Reviews. We calculated summary effects using random-effects models, and we assessed between-study heterogeneity. We estimated whether large studies had significantly more conservative results compared to smaller studies (small-study effects) and whether the observed positive studies were more than expected by chance. Finally, we assessed the credibility of the evidence using several criteria.

RESULTS

One hundred and ninety-nine meta-analyses were significant at P-value ≤ 0.05, and almost all (n = 196) favoured psychotherapy. Large and very large heterogeneity was observed in 130 meta-analyses. Evidence for small-study effects was found in 72 meta-analyses, while 95 had evidence of excess of significant findings. Only 16 (7%) provided convincing evidence that psychotherapy is effective. These pertained to cognitive behavioural therapy (n = 6), meditation therapy (n = 1), cognitive remediation (n = 1), counselling (n = 1) and mixed types of psychotherapies (n = 7).

CONCLUSIONS

Although almost 80% meta-analyses reported a nominally statistically significant finding favouring psychotherapy, only a few meta-analyses provided convincing evidence without biases.

An umbrella review of the literature on the effectiveness of psychological interventions for pain reduction

BACKGROUND

Psychological interventions are widely implemented for pain management and treatment, but their reported effectiveness shows considerable variation and there is elevated likelihood for bias.

METHODS

We summarized the strength of evidence and extent of potential biases in the published literature of psychological interventions for pain treatment using a range of criteria, including the statistical significance of the random effects summary estimate and of the largest study of each meta-analysis, number of participants, 95% prediction intervals, between-study heterogeneity, small-study effects and excess significance bias.

RESULTS

Thirty-eight publications were identified, investigating 150 associations between several psychological interventions and 29 different types of pain. Of the 141 associations based on only randomized controlled trials, none presented strong or highly suggestive evidence by satisfying all the aforementioned criteria. The effect of psychological interventions on reducing cancer pain severity, pain in patients with arthritis, osteoarthritis, rheumatoid arthritis, breast cancer, fibromyalgia, irritable bowel syndrome, self-reported needle-related pain in children/adolescents or with chronic musculoskeletal pain, chronic non-headache pain and chronic pain in general were supported by suggestive evidence.

CONCLUSIONS

The present findings reveal the lack of strong supporting empirical evidence for the effectiveness of psychological treatments for pain management and highlight the need to further evaluate the established approach of psychological interventions to ameliorate pain.

Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis

PURPOSE

To establish whether the association between milk intake and prostate cancer operates via the insulin-like growth factor (IGF) pathway (including IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3).

METHODS

Systematic review, collating data from all relevant studies examining associations of milk with IGF, and those examining associations of IGF with prostate cancer risk and progression. Data were extracted from experimental and observational studies conducted in either humans or animals, and analyzed using meta-analysis where possible, with summary data presented otherwise.

RESULTS

One hundred and seventy-two studies met the inclusion criteria: 31 examining the milk-IGF relationship; 132 examining the IGF-prostate cancer relationship in humans; and 10 animal studies examining the IGF-prostate cancer relationship. There was moderate evidence that circulating IGF-I and IGFBP-3 increase with milk (and dairy protein) intake (an estimated standardized effect size of 0.10 SD increase in IGF-I and 0.05 SD in IGFBP-3 per 1 SD increase in milk intake). There was moderate evidence that prostate cancer risk increased with IGF-I (Random effects meta-analysis OR per SD increase in IGF-I 1.09; 95% CI 1.03, 1.16; n = 51 studies) and decreased with IGFBP-3 (OR 0.90; 0.83, 0.98; n = 39 studies), but not with other growth factors. The IGFBP-3 -202A/C single nucleotide polymorphism was positively associated with prostate cancer (pooled OR for A/C vs. AA = 1.22; 95% CI 0.84, 1.79; OR for C/C vs. AA = 1.51; 1.03, 2.21, n = 8 studies). No strong associations were observed for IGF-II, IGFBP-1 or IGFBP-2 with either milk intake or prostate cancer risk. There was little consistency within the data extracted from the small number of animal studies. There was additional evidence to suggest that the suppression of IGF-II can reduce tumor size, and contradictory evidence with regards to the effect of IGFBP-3 suppression on tumor progression.

CONCLUSION

IGF-I is a potential mechanism underlying the observed associations between milk intake and prostate cancer risk.

Cancer and central nervous system disorders: protocol for an umbrella review of systematic reviews and updated meta-analyses of observational studies

BACKGROUND

The objective of this study will be to synthesize the epidemiological evidence and evaluate the validity of the associations between central nervous system disorders and the risk of developing or dying from cancer.

METHODS/DESIGN

We will perform an umbrella review of systematic reviews and conduct updated meta-analyses of observational studies (cohort and case-control) investigating the association between central nervous system disorders and the risk of developing or dying from any cancer or specific types of cancer. Searches involving PubMed/MEDLINE, EMBASE, SCOPUS and Web of Science will be used to identify systematic reviews and meta-analyses of observational studies. In addition, online databases will be checked for observational studies published outside the time frames of previous reviews. Eligible central nervous system disorders will be Alzheimer's disease, anorexia nervosa, amyotrophic lateral sclerosis, autism spectrum disorders, bipolar disorder, depression, Down's syndrome, epilepsy, Huntington's disease, multiple sclerosis, Parkinson's disease and schizophrenia. The primary outcomes will be cancer incidence and cancer mortality in association with a central nervous system disorder. Secondary outcome measures will be site-specific cancer incidence and mortality, respectively. Two reviewers will independently screen references identified by the literature search, as well as potentially relevant full-text articles. Data will be abstracted, and study quality/risk of bias will be appraised by two reviewers independently. Conflicts at all levels of screening and abstraction will be resolved through discussion. Random-effects meta-analyses of primary observational studies will be conducted where appropriate. Parameters for exploring statistical heterogeneity are pre-specified. The World Cancer Research Fund (WCRF)/American Institute for Cancer Research (AICR) criteria and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be used for determining the quality of evidence for cancer outcomes.

DISCUSSION

Our study will establish the extent of the epidemiological evidence underlying the associations between central nervous system disorders and cancer and will provide a rigorous and updated synthesis of a range of important site-specific cancer outcomes.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016052762.

Adiposity and cancer at major anatomical sites: umbrella review of the literature

Objective To evaluate the strength and validity of the evidence for the association between adiposity and risk of developing or dying from cancer.Design Umbrella review of systematic reviews and meta-analyses.Data sources PubMed, Embase, Cochrane Database of Systematic Reviews, and manual screening of retrieved references.Eligibility criteria Systematic reviews or meta-analyses of observational studies that evaluated the association between indices of adiposity and risk of developing or dying from cancer.Data synthesis Primary analysis focused on cohort studies exploring associations for continuous measures of adiposity. The evidence was graded into strong, highly suggestive, suggestive, or weak after applying criteria that included the statistical significance of the random effects summary estimate and of the largest study in a meta-analysis, the number of cancer cases, heterogeneity between studies, 95% prediction intervals, small study effects, excess significance bias, and sensitivity analysis with credibility ceilings.Results 204 meta-analyses investigated associations between seven indices of adiposity and developing or dying from 36 primary cancers and their subtypes. Of the 95 meta-analyses that included cohort studies and used a continuous scale to measure adiposity, only 12 (13%) associations for nine cancers were supported by strong evidence. An increase in body mass index was associated with a higher risk of developing oesophageal adenocarcinoma; colon and rectal cancer in men; biliary tract system and pancreatic cancer; endometrial cancer in premenopausal women; kidney cancer; and multiple myeloma. Weight gain and waist to hip circumference ratio were associated with higher risks of postmenopausal breast cancer in women who have never used hormone replacement therapy and endometrial cancer, respectively. The increase in the risk of developing cancer for every 5 kg/m2 increase in body mass index ranged from 9% (relative risk 1.09, 95% confidence interval 1.06 to 1.13) for rectal cancer among men to 56% (1.56, 1.34 to 1.81) for biliary tract system cancer. The risk of postmenopausal breast cancer among women who have never used HRT increased by 11% for each 5 kg of weight gain in adulthood (1.11, 1.09 to 1.13), and the risk of endometrial cancer increased by 21% for each 0.1 increase in waist to hip ratio (1.21, 1.13 to 1.29). Five additional associations were supported by strong evidence when categorical measures of adiposity were included: weight gain with colorectal cancer; body mass index with gallbladder, gastric cardia, and ovarian cancer; and multiple myeloma mortality.Conclusions Although the association of adiposity with cancer risk has been extensively studied, associations for only 11 cancers (oesophageal adenocarcinoma, multiple myeloma, and cancers of the gastric cardia, colon, rectum, biliary tract system, pancreas, breast, endometrium, ovary, and kidney) were supported by strong evidence. Other associations could be genuine, but substantial uncertainty remains. Obesity is becoming one of the biggest problems in public health; evidence on the strength of the associated risks may allow finer selection of those at higher risk of cancer, who could be targeted for personalised prevention strategies.

Diet, body size, physical activity and risk of prostate cancer: An umbrella review of the evidence

The existing literature on the relationship between diet, body size, physical activity and prostate cancer risk was summarised by the World Cancer Research Fund Continuous Update Project (CUP). An evaluation of the robustness of this evidence is required to help inform public health policy. The robustness of this evidence was evaluated using several criteria addressing evidence strength and validity, including the statistical significance of the random effects summary estimate and of the largest study in a meta-analysis, number of prostate cancer cases, between-study heterogeneity, 95% prediction intervals, small-study effects bias, excess significance bias and sensitivity analyses with credibility ceilings. A total of 248 meta-analyses were extracted from the CUP, which studied associations of 23 foods, 31 nutrients, eight indices of body size and three indices of physical activity with risk of total prostate cancer development, mortality or cancer development by stage and grade. Of the 176 meta-analyses using a continuous scale to measure the exposures, no association presented strong evidence by satisfying all the aforementioned criteria. Only the association of height with total prostate cancer incidence and mortality presented highly suggestive evidence with a 4% higher risk per 5 cm greater height (95% confidence interval, 1.03, 1.05). Associations for body mass index, weight, height, dietary calcium and spirits intake were supported by suggestive evidence. Overall, the association of diet, body size, physical activity and prostate cancer has been extensively studied, but no association was graded with strong evidence.

Bias in emerging biomarkers for bipolar disorder

BACKGROUND

To date no comprehensive evaluation has appraised the likelihood of bias or the strength of the evidence of peripheral biomarkers for bipolar disorder (BD). Here we performed an umbrella review of meta-analyses of peripheral non-genetic biomarkers for BD.

METHOD

The Pubmed/Medline, EMBASE and PsycInfo electronic databases were searched up to May 2015. Two independent authors conducted searches, examined references for eligibility, and extracted data. Meta-analyses in any language examining peripheral non-genetic biomarkers in participants with BD (across different mood states) compared to unaffected controls were included.

RESULTS

Six references, which examined 13 biomarkers across 20 meta-analyses (5474 BD cases and 4823 healthy controls) met inclusion criteria. Evidence for excess of significance bias (i.e. bias favoring publication of 'positive' nominally significant results) was observed in 11 meta-analyses. Heterogeneity was high for (I 2 ⩾ 50%) 16 meta-analyses. Only two biomarkers met criteria for suggestive evidence namely the soluble IL-2 receptor and morning cortisol. The median power of included studies, using the effect size of the largest dataset as the plausible true effect size of each meta-analysis, was 15.3%.

CONCLUSIONS

Our findings suggest that there is an excess of statistically significant results in the literature of peripheral biomarkers for BD. Selective publication of 'positive' results and selective reporting of outcomes are possible mechanisms.

The Obesity-Breast Cancer Conundrum: An Analysis of the Issues

Breast cancer develops over a timeframe of 2-3 decades prior to clinical detection. Given this prolonged latency, it is somewhat unexpected from a biological perspective that obesity has no effect or reduces the risk for breast cancer in premenopausal women yet increases the risk for breast cancer in postmenopausal women. This conundrum is particularly striking in light of the generally negative effects of obesity on breast cancer outcomes, including larger tumor size at diagnosis and poorer prognosis in both pre- and postmenopausal women. This review and analysis identifies factors that may contribute to this apparent conundrum, issues that merit further investigation, and characteristics of preclinical models for breast cancer and obesity that should be considered if animal models are used to deconstruct the conundrum.

Body mass index and risk of colorectal cancer according to tumor lymphocytic infiltrate

Higher body mass index (BMI), higher body adiposity and obesity have been associated with increased risk of colorectal cancer. Evidence suggests that excess energy balance may influence systemic immune and inflammatory status. Thus, we hypothesized that the positive association between BMI and colorectal cancer risk might differ according to colorectal carcinoma subtypes according to levels of histopathological lymphocytic reaction to tumor. We collected biennial questionnaire data on weight and baseline height information in two prospective cohort studies, the Nurses' Health Study (1980-2010) and the Health Professionals Follow-up Study (1986-2010). Utilizing duplication-method Cox proportional hazards regression models, we prospectively assessed the association between BMI and risk of colorectal cancer subtypes according to the degree of Crohn's-like lymphoid reaction, peritumoral lymphocytic reaction, intratumoral periglandular reaction, tumor-infiltrating lymphocytes, the overall lymphocytic reaction score, or T-cell [CD3(+) , CD8(+) , CD45RO (PTPRC)(+) or FOXP3(+) ] density in tumor tissue. Statistical significance level was adjusted for multiple hypotheses testing by Bonferroni correction. During follow up of 1,708,029 men and women (over 3,346,752 person-years), we documented 1,436 incident rectal and colon cancer cases with available formalin-fixed paraffin-embedded tumor tissue materials and pathological immunity data. BMI was significantly associated with higher risk of overall colorectal cancer (Ptrend  < 0.001); however, the association of BMI with colorectal carcinoma risk did not significantly differ by the level of lymphocytic reaction or T-cell infiltration in tumor tissue status (Pheterogeneity  > 0.10). BMI may be associated with risk of colorectal cancer regardless of levels of lymphocytic response to tumor.

Planning clinically relevant biomarker validation studies using the "number needed to treat" concept

Purpose

Despite an explosion of translational research to exploit biomarkers in diagnosis, prediction and prognosis, the impact of biomarkers on clinical practice has been limited. The elusiveness of clinical utility may partly originate when validation studies are planned, from a failure to articulate precisely how the biomarker, if successful, will improve clinical decision-making for patients. Clarifying what performance would suffice if the test is to improve medical care makes it possible to design meaningful validation studies. But methods for tackling this part of validation study design are undeveloped, because it demands uncomfortable judgments about the relative values of good and bad outcomes resulting from a medical decision.

Methods

An unconventional use of “number needed to treat” (NNT) can structure communication for the trial design team, to elicit purely value-based outcome tradeoffs, conveyed as the endpoints of an NNT “discomfort range”. The study biostatistician can convert the endpoints into desired predictive values, providing criteria for designing a prospective validation study. Next, a novel “contra-Bayes” theorem converts those predictive values into target sensitivity and specificity criteria, to guide design of a retrospective validation study. Several examples demonstrate the approach.

Conclusion

In practice, NNT-guided dialogues have contributed to validation study planning by tying it closely to specific patient-oriented translational goals. The ultimate payoff comes when the report of the completed study includes motivation in the form of a biomarker test framework directly reflecting the clinical decision challenge to be solved. Then readers will understand better what the biomarker test has to offer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0862-4) contains supplementary material, which is available to authorized users.

Circulating insulin-like growth factor-I, insulin-like growth factor binding protein-3 and terminal duct lobular unit involution of the breast: a cross-sectional study of women with benign breast disease

Background

Terminal duct lobular units (TDLUs) are the primary structures from which breast cancers and their precursors arise. Decreased age-related TDLU involution and elevated mammographic density are both correlated and independently associated with increased breast cancer risk, suggesting that these characteristics of breast parenchyma might be linked to a common factor. Given data suggesting that increased circulating levels of insulin-like growth factors (IGFs) factors are related to reduced TDLU involution and increased mammographic density, we assessed these relationships using validated quantitative methods in a cross-sectional study of women with benign breast disease.

Methods

Serum IGF-I, IGFBP-3 and IGF-I:IGFBP-3 molar ratios were measured in 228 women, ages 40-64, who underwent diagnostic breast biopsies yielding benign diagnoses at University of Vermont affiliated centers. Biopsies were assessed for three separate measures inversely related to TDLU involution: numbers of TDLUs per unit of tissue area (“TDLU count”), median TDLU diameter (“TDLU span”), and number of acini per TDLU (“acini count”). Regression models, stratified by menopausal status and adjusted for potential confounders, were used to assess the associations of TDLU count, median TDLU span and median acini count per TDLU with tertiles of circulating IGFs. Given that mammographic density is associated with both IGF levels and breast cancer risk, we also stratified these associations by mammographic density.

Results

Higher IGF-I levels among postmenopausal women and an elevated IGF-I:IGFBP-3 ratio among all women were associated with higher TDLU counts, a marker of decreased lobular involution (P-trend = 0.009 and <0.0001, respectively); these associations were strongest among women with elevated mammographic density (P-interaction <0.01). Circulating IGF levels were not significantly associated with TDLU span or acini count per TDLU.

Conclusions

These results suggest that elevated IGF levels may define a sub-group of women with high mammographic density and limited TDLU involution, two markers that have been related to increased breast cancer risk. If confirmed in prospective studies with cancer endpoints, these data may suggest that evaluation of IGF signaling and its downstream effects may have value for risk prediction and suggest strategies for breast cancer chemoprevention through inhibition of the IGF system.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0678-4) contains supplementary material, which is available to authorized users.

Adiposity and cancer risk: new mechanistic insights from epidemiology

Excess body adiposity, commonly expressed as body mass index (BMI), is a risk factor for many common adult cancers. Over the past decade, epidemiological data have shown that adiposity-cancer risk associations are specific for gender, site, geographical population, histological subtype and molecular phenotype. The biological mechanisms underpinning these associations are incompletely understood but need to take account of the specificities observed in epidemiology to better inform future prevention strategies.

Interleukin-6 and risk of colorectal cancer: results from the CLUE II cohort and a meta-analysis of prospective studies

PURPOSE

The association between prediagnostic interleukin-6 (IL-6) concentrations and risk of colorectal cancer was evaluated in a nested case-control study and a meta-analysis of prospective studies.

METHODS

Colorectal cancer cases (n = 173) and matched controls (n = 345) were identified between 1989 and 2000 among participants in the CLUE II cohort of Washington Country, Maryland. Matched odds ratios and the corresponding 95 % confidence intervals (CIs) were estimated using conditional logistic regression models.

RESULTS

Participants in the highest third of plasma IL-6 concentration had a 2.48 times higher risk of colon cancer compared to participants in the bottom third (95 % CI 1.26-4.87; p-trend 0.02) after multivariate adjustment. This association did not differ according to the stage of disease, age, sex, or other potential modifying variables and remained statistically significant after adjustment for C-reactive protein concentrations. No statistically significant association was observed for rectal cancer risk. The meta-analysis of six prospective studies yielded an increased but borderline statistically significant risk of colon cancer per 1 U increase in naturally logarithm-transformed IL-6 (summary RR 1.22; 95 % CI 1.00-1.49; I (2) 46 %). An inverse association was noted for rectal cancer (RR 0.69; 95 % CI 0.54-0.88; I (2) 0 %), but there was evidence for small-study effects (p 0.02).

CONCLUSION

Our findings provide support for a modest positive association between IL-6 concentrations and colon cancer risk. More work is needed to determine whether IL-6 is a valid marker of colorectal inflammation and whether such inflammation contributes to colon and rectal cancer risk.

Biomarkers of Inflammation and Immune Function and Risk of Colorectal Cancer

A substantial number of prospective epidemiological studies have been conducted to investigate the association between biomarkers of inflammation and immune function and risk of colorectal cancer. Although pre-diagnostic concentrations of these biomarkers, especially C-reactive protein, have been associated with a higher risk of colorectal cancer in some studies, this association does not seem to have a robust support without hints of bias. Future prospective studies should evaluate multiple inflammatory biomarkers with longitudinal measures over the follow-up taking advantage of new multiplex cytokine quantification arrays and use more sophisticated joint or biomarker pattern statistical approaches to capture the complex and dynamic interplay between biomarkers and risk of colorectal cancer. Large collaborative consortia and Mendelian randomization studies should be encouraged to diminish the threat of biases and improve the reliability of this literature.

Biomarkers for Helicobacter pylori infection and gastroduodenal diseases

Helicobacter pylori infection is a major cause of gastric cancer. Although identifying H. pylori infected subjects is the first approach for delineating the high-risk population for gastric cancer, the presence of H. pylori antibodies is not sufficient for gastric cancer screening. Among H. pylori infected subjects, only a minority of infected individuals develop gastric cancer. Serologic markers of H. pylori infection can serve as potential predictors for the development of gastric cancer. Serum or urinary H. pylori antibodies, cytotoxin-associated gene A antibodies, pepsinogen and microRNAs were reported to be associated with precancerous lesions or gastric cancer. In this review, we summarized the utilities and limitations of each strategy.

The Replication Paradox: Combining Studies can Decrease Accuracy of Effect Size Estimates

Replication is often viewed as the demarcation between science and nonscience. However, contrary to the commonly held view, we show that in the current (selective) publication system replications may increase bias in effect size estimates. Specifically, we examine the effect of replication on bias in estimated population effect size as a function of publication bias and the studies’ sample size or power. We analytically show that incorporating the results of published replication studies will in general not lead to less bias in the estimated population effect size. We therefore conclude that mere replication will not solve the problem of overestimation of effect sizes. We will discuss the implications of our findings for interpreting results of published and unpublished studies, and for conducting and interpreting results of meta-analyses. We also discuss solutions for the problem of overestimation of effect sizes, such as discarding and not publishing small studies with low power, and implementing practices that completely eliminate publication bias (e.g., study registration).