Randomised trials comparing chemotherapy regimens for advanced non-small cell lung cancer: biases and evolution over time

An Evaluation of Reporting Guidelines and Clinical Trial Registry Requirements Among Orthopaedic Surgery Journals

BACKGROUND

The responsibility for ensuring that studies are adequately reported is primarily that of those conducting the study; however, journal policies may influence how thoroughly authors choose to report their research. The use of reporting guidelines and prospective trial registration are promising avenues for ensuring that published studies adhere to the highest methodological standards. The purpose of this study is to evaluate orthopaedic surgery journal policies regarding reporting guidelines and trial registration, and to evaluate the effects that these policies have on adherence to reporting.

METHODS

We conducted a cross-sectional survey of journal policies and "Instructions for Authors" to determine the journals' policies and guidance regarding use of reporting guidelines and study registration. We also examined whether trials published in journals referencing CONSORT (Consolidated Standards of Reporting Trials) had higher rates of compliance with publishing a CONSORT flow diagram and whether journals with trial registration policies were more likely to contain registered trials than journals without these requirements.

RESULTS

Of the 21 orthopaedic surgery journals, 6 (29%) did not mention a single guideline, and clinical trial registration was required by 11 (52%) orthopaedic surgery journals and recommended by 2 (10%). Of the 21 general medical journals, 3 (14%) did not mention a single guideline, and trial registration was required by 13 (62%) general medical journals and recommended by 5 (24%) others. Furthermore, journals that referenced CONSORT were more likely to publish trials with a CONSORT flow diagram. Journals with trial registration policies were more likely to publish registered trials.

CONCLUSIONS

Reporting guidelines and trial registration are suboptimally required or recommended by orthopaedic surgery journals. These 2 mechanisms may improve methodology and quality, and should be considered for adoption by journal editors in orthopaedic surgery.

CLINICAL RELEVANCE

Because orthopaedic surgeons rely on high-quality research to direct patient care, measures must be taken to ensure that published research is of the highest quality. The use of reporting guidelines and prospective clinical trial registration may improve the quality of orthopaedic research, thereby improving patient care.

Incidence of Neutropenia in Veterans Receiving Lung Cancer Chemotherapy: A Comparison of Administrative Coding and Electronic Laboratory Data

Introduction:

The frequency of neutropenia associated with lung cancer chemotherapy outside of randomized trials is largely unknown because administrative coding underestimates its prevalence. This study compared International Classification of Diseases (ICD) diagnosis codes and electronic laboratory results, alone and in combination, for identifying neutropenia events.

Methods:

Retrospective cohort study of 718 veterans receiving their first course of chemotherapy for non-small cell lung cancer. Incidence of neutropenia was assessed using electronic laboratory results and ICD-9 codes captured in the Department of Veterans Affairs (VA) electronic medical records (EMR).

Results:

A total of 118 of 718 patients (16.4 percent) were identified with an absolute neutrophil count (ANC) less than 1,000 cells/mm³, while only 49 of 718 patients (6.8 percent) had ICD-9 codes for neutropenia. Using the combination of laboratory results and diagnosis codes, 136 of 718 patients (18.9 percent) experienced a neutropenic event. Compared to laboratory results as a gold standard, diagnosis codes were specific (not present for individuals without a laboratory-documented low ANC), but not sensitive (missing for many individuals with a low ANC documented in their laboratory test results).

Conclusion:

Relying on ICD codes to identify neutropenia in administrative data likely results in under-reporting. The emerging availability of electronic laboratory results provides an opportunity to more accurately quantify patterns of neutropenia, identify individual risk factors, and assess clinical management practices—including use of colony-stimulating factor prophylaxis—in large community cohorts.

Trends in phase III randomized controlled clinical trials on the treatment of advanced non-small-cell lung cancer

The objective of this review was to analyze trends in outcomes and in the quality of phase III randomized controlled trials on advanced NSCLC published between 2000 and 2012, selecting 76 trials from a total of 122 retrieved in a structured search. Over the study period, the number of randomized patients per trial increased by 14 per year (P = 0.178). The sample size significantly increased between 2000 and 2012 in trials of targeted agents (460.1 vs. 740.8 patients, P = 0.009), trials of >1 drug (360.4 vs. 584.8, P = 0.014), and those including patients with good performance status (675.3 vs. 425.6; P = 0.003). Quality of life was assessed in 46 trials (60.5%), and significant improvements were reported in 10 of these (21.7%). Platinum-based regimens were the most frequently investigated (86.8% of trials). Molecular-targeted agents were studied in 25.0% of chemotherapy arms, and the percentage of trials including these agents increased each year. The median (interquartile range) overall survival (MOS) was 9.90 (3.5) months with an increase of 0.384 months per year of publication (P < 0.001). A statistically significant improvement in MOS was obtained in only 13 (18.8%) trials. The median progression-free survival was 4.9 (1.9) months, with a nonsignificant increase of 0.026 months per year (P > 0.05). There has been a continuous but modest improvement in the survival of patients with advanced NSCLC over the past 12 years. Nevertheless, the quality of clinical trials and the benefit in outcomes should be carefully considered before the incorporation of novel approaches into clinical practice.

Treatment and outcome of patients with metastatic NSCLC: a retrospective institution analysis of 493 patients

Background

Most patients with metastatic non-small cell lung cancer (NSCLC) will face treatment with systemic therapy. Current clinical studies are demonstrating improvements in chemotherapy and overall survival. However, it remains unclear whether these results are translated into clinical practice.

Methods

We reviewed all stage IV NSCLC patients without second malignancies that were diagnosed from 2004 to 2006 at our institution. 493 consecutive patients were included into this retrospective analysis and were followed-up until end of 2011.

Results

352 patients (71.4%) received systemic therapy for up to 7 lines. For most patients, adjustments of dosages or applications had to be made at some point of the treatment, but the total applied dose remained generally close to the intended dose. The best disease control (BDC) rate decreased with increasing therapy lines from 59.7% to about 35%. Patients with palliative local therapy but no systemic treatment demonstrated inferior survival (median 2.9 versus 8.7 months, p < 0.001). The median interval between last treatment and death was 50 days and 15 days for chemotherapy and anti-EGFR therapy, respectively. BDC to the previous therapy lines was predictive for improved BDC to third- but not second-line therapy. Performing multivariate analysis, BDC to previous therapy, never-/ former-smoking status, and age > 70 years were associated with improved survival performing third-line therapy.

Conclusions

Stage IV NSCLC patients may receive substantial systemic therapy resulting in response and median survival rates that are comparable to data from clinical studies. However, preselection factors are increasingly important to improve therapy outcome and life quality.

Risk of bias of randomized controlled trials published in orthopaedic journals

Background

The purpose of this study was to assess the quality of methodology in orthopaedics-related randomized controlled trials (RCTs) published from January 2006 to December 2010 in the top orthopaedic journals based on impact scores from the Thompson ISI citation reports (2010).

Methods

Journals included American Journal of Sports Medicine; Journal of Orthopaedic Research; Journal of Bone and Joint Surgery, American; Spine Journal; and Osteoarthritis and Cartilage. Each RCT was assessed on ten criteria (randomization method, allocation sequence concealment, participant blinding, outcome assessor blinding, outcome measurement, interventionist training, withdrawals, intent to treat analyses, clustering, and baseline characteristics) as having empirical evidence for biasing treatment effect estimates when not performed properly.

Results

A total of 232 RCTs met our inclusion criteria. The proportion of RCTs in published journals fell from 6% in 2006 to 4% in 2010. Forty-nine percent of the criteria were fulfilled across these journals, with 42% of the criteria not being amendable to assessment due to inadequate reporting. The results of our regression revealed that a more recent publication year was significantly associated with more fulfilled criteria (β = 0.171; CI = −0.00 to 0.342; p = 0.051).

Conclusion

In summary, very few studies met all ten criteria. Thus, many of these studies likely have biased estimates of treatment effects. In addition, these journals had poor reporting of important methodological aspects.

Inference for meta-analysis with a suspected temporal trend

There is sometimes a clear evidence of a strong secular trend in the treatment effect of studies included in a meta-analysis. In such cases, estimating the present-day treatment effect by meta-regression is both reasonable and straightforward. We however consider the more common situation where a secular trend is suspected, but is not strongly statistically significant. Typically, this lack of significance is due to the small number of studies included in the analysis, so that a meta-regression could give wild point estimates. We introduce an empirical Bayes meta-analysis methodology, which shrinks the secular trend toward zero. This has the effect that treatment effects are adjusted for trend, but where the evidence from data is weak, wild results are not obtained. We explore several frequentist approaches and a fully Bayesian method is also implemented. A measure of trend analogous to I(2) is described, and exact significance tests for trend are given. Our preferred method is one based on penalized or h-likelihood, which is computationally simple, and allows invariance of predictions to the (arbitrary) choice of time origin. We suggest that a trendless standard random effects meta-analysis should routinely be supplemented with an h-likelihood analysis as a sensitivity analysis.

Emerging techniques for determining the tissue of origin in patients with unknown primary carcinoma

New molecular tests to assign a putative tissue of origin in patients with carcinoma of unknown primary (CUP) have recently become commercially available. This editorial addresses this new technology in terms of our current understanding of CUP, and how these tests may affect its management.

Somatic EGFR mutation and gene copy gain as predictive biomarkers for response to tyrosine kinase inhibitors in non-small cell lung cancer

PURPOSE

The aim of this systematic review and meta-analysis was to characterize common EGFR molecular aberrations as potential predictive biomarkers for response to monotherapy with tyrosine kinase inhibitors (TKI) in non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

We systematically identified articles investigating EGFR status [somatic mutational and gene copy aberrations (copy number)] in patients with NSCLC treated with TKIs. Eligible studies had to report complete and partial response rates stratified by EGFR status. We used random effects models for bivariable meta-analysis of sensitivity and specificity; positive and negative likelihood ratios (+LR and -LR, respectively) were also calculated and were considered as secondary end points.

RESULTS

Among 222 retrieved articles, 59 were considered eligible for the somatic EGFR mutation meta-analysis (1,020 mutations among 3,101 patients) and 21 were considered eligible for the EGFR gene copy number meta-analysis (542 gene gain among 1,539 patients). EGFR mutations were predictive of response to single-agent TKIs [sensitivity, 0.78; 95% confidence interval (95% CI), 0.74-0.82; specificity, 0.86; 95% CI, 0.82-0.89; +LR, 5.6; -LR, 0.25]. EGFR gene gain was also associated with response to TKIs, albeit with lower sensitivity and specificity. In subgroup analysis, the only recognized trend was for a higher predictive value in Whites compared with East Asians for both mutation and gene copy number.

CONCLUSION

This analysis provides empirical evidence that EGFR mutations are sensitive and specific predictors of response to single-agent epidermal growth factor receptor TKIs in advanced NSCLC. The diagnostic performance of mutations seems better than that of EGFR gene gain.

Association of trial registration with the results and conclusions of published trials of new oncology drugs

BACKGROUND

Registration of clinical trials has been introduced largely to reduce bias toward statistically significant results in the trial literature. Doubts remain about whether advance registration alone is an adequate measure to reduce selective publication, selective outcome reporting, and biased design. One of the first areas of medicine in which registration was widely adopted was oncology, although the bulk of registered oncology trials remain unpublished. The net influence of registration on the literature remains untested. This study compares the prevalence of favorable results and conclusions among published reports of registered and unregistered randomized controlled trials of new oncology drugs.

METHODS

We conducted a cross-sectional study of published original research articles reporting clinical trials evaluating the efficacy of drugs newly approved for antimalignancy indications by the United States Food and Drug Administration (FDA) from 2000 through 2005. Drugs receiving first-time approval for indications in oncology were identified using the FDA web site and Thomson Centerwatch. Relevant trial reports were identified using PubMed and the Cochrane Library. Evidence of advance trial registration was obtained by a search of clinicaltrials.gov, WHO, ISRCTN, NCI-PDQ trial databases and corporate trial registries, as well as articles themselves. Data on blinding, results for primary outcomes, and author conclusions were extracted independently by two coders. Univariate and multivariate logistic regression identified associations between favorable results and conclusions and independent variables including advance registration, study design characteristics, and industry sponsorship.

RESULTS

Of 137 original research reports from 115 distinct randomized trials assessing 25 newly approved drugs for treating cancer, the 54 publications describing data from trials registered prior to publication were as likely to report statistically significant efficacy results and reach conclusions favoring the test drug (for results, OR = 1.77; 95% CI = 0.87 to 3.61) as reports of trials not registered in advance. In multivariate analysis, reports of prior registered trials were again as likely to favor the test drug (OR = 1.29; 95% CI = 0.54 to 3.08); large sample sizes and surrogate outcome measures were statistically significant predictors of favorable efficacy results at p < 0.05. Subgroup analysis of the main reports from each trial (n = 115) similarly indicated that registered trials were as likely to report results favoring the test drug as trials not registered in advance (OR = 1.11; 95% CI = 0.44 to 2.80), and also that large trials and trials with nonstringent blinding were significantly more likely to report results favoring the test drug.

CONCLUSIONS

Trial registration alone, without a requirement for full reporting of research results, does not appear to reduce a bias toward results and conclusions favoring new drugs in the clinical trials literature. Our findings support the inclusion of full results reporting in trial registers, as well as protocols to allow assessment of whether results have been completely reported.

Factors associated with results and conclusions of trials of thiazolidinediones

Background

When a sponsor funds a study of two competing drugs in a head-to-head comparison, the results and conclusions are likely to favor the sponsor’s drug. Thiazolidinediones, oral medications used for the treatment of type 2 diabetes, are one of the most costly choices of oral anti-diabetic medications, yet they do not demonstrate clinically relevant differences in achieving lower glycosylated hemoglobin levels compared to other oral antidiabetic drugs. Our aim is to examine associations between research funding source, study design characteristics aimed at reducing bias, and other factors with the results and conclusions of randomized controlled trials (RCTs) of thiazolidinediones compared to other oral hypoglycemic agents.

Methods and Findings

This is a cross-sectional study of 61 published RCTs comparing a thiazolidinedione (glitazone) to another anti-diabetic drug or placebo for treatment of type 2 diabetes. Data on study design characteristics, funding source, author’s financial ties, results for primary outcomes, and author conclusions were extracted. Univariate logistic regression identified associations between independent variables and results and conclusions that favored the glitazone. Of the RCTs, 59% (36/61) were funded by industry, 39% (24/61) did not disclose any funding. Common study design weaknesses included inadequate blinding and lack of concealment of allocation. Trials that reported favorable glycemic control results for the glitazone were more likely to have adequate blinding (OR (95% CI)  = 5.42 (1.46, 21.19), p = 0.008) and have a corresponding author with financial ties to the glitazone manufacturer (OR (95% CI)  = 4.12 (1.05, 19.53); p = 0.04). Trials with conclusions favoring the glitazone were less likely to be funded by a comparator drug company than a glitazone company (OR (95% CI)  = 0.026 (0, 0.40), p = 0.003) and less likely to be published in journals with higher impact factors (OR (95% CI)  = 0.79 (0.62, 0.97), p = 0.011). One limitation of our study is that we categorized studies as funded by industry based on each article’s disclosure which could underestimate the number of industry sponsored studies and personal ties of investigators. Additionally, our study did not include any head-to-head comparisons of one glitazone to another.

Conclusions

Published RCT comparisons of glitazones with other anti-diabetic drugs or placebo are predominantly industry supported and this support, as well as the financial ties of study authors, appears to be associated with favorable findings.

In a review of stroke rehabilitation studies, concealed allocation was under reported

OBJECTIVE

The objective of this two-phase study was to assess the adequacy of the reporting of concealed allocation (CA) in randomized controlled trials (RCTs) evaluating interventions associated with stroke rehabilitation.

STUDY DESIGN AND SETTING

In phase I of the study, 50 RCTs included in a systematic review were selected to establish agreement between two raters. Two investigators determined if the method described to conceal the randomization schedule was adequate, inadequate, or not reported. In phase II, using a larger sample size (n=165), the differences in the proportion of studies with and without adequate CA are reported for two comparisons: (1) pharmacological vs. nonpharmacological trials and (2) multicentered vs. single-site studies.

RESULTS

In both phases I and II, CA was described adequately in one-third of all studies sampled. The agreement between raters was 88% (small ka, Cyrillic=0.79; 95% confidence interval: 0.65, 0.94). No significant differences in the adequacy of reporting for CA were found with respect to study type (pharmacological vs. nonpharmacological), whereas multicentered trials reported adequacy of CA more frequently.

CONCLUSION

Although concealment of group allocation is an important feature of trial design, it was frequently not reported in many RCTs associated with stroke rehabilitation.

Evolution of the randomized controlled trial in oncology over three decades

PURPOSE

The randomized controlled trial (RCT) is the gold standard for establishing new therapies in clinical oncology. Here we document changes with time in design, sponsorship, and outcomes of oncology RCTs.

METHODS

Reports of RCTs evaluating systemic therapy for breast, colorectal (CRC), and non-small-cell lung cancer (NSCLC) published 1975 to 2004 in six major journals were reviewed. Two authors abstracted data regarding trial design, results, and conclusions. Conclusions of authors were graded using a 7-point Likert scale. For each study the effect size for the primary end point was converted to a summary measure.

RESULTS

A total of 321 eligible RCTs were included (48% breast, 24% CRC, 28% NSCLC). Over time, the number and size of RCTs increased considerably. For-profit/mixed sponsorship increased substantially during the study period (4% to 57%; P < .001). There was increasing use of time-to-event measures (39% to 78%) and decreasing use of response rate (54% to 14%) as primary end point (P < .001). Effect size remained stable over the study period. Authors have become more likely to strongly endorse the experimental arm (P = .017). A significant P value for the primary end point and industry sponsorship were each independently associated with endorsement of the experimental agent (odds ratio [OR] = 19.6, 95% CI, 8.9 to 43.1, and OR = 3.5, 95% CI, 1.6 to 7.5, respectively).

CONCLUSION

RCTs in oncology have become larger and are more likely to be sponsored by industry. Authors of modern RCTs are more likely to strongly endorse novel therapies. For-profit sponsorship and statistically significant results are independently associated with endorsement of the experimental arm.

Evaluation of networks of randomized trials

Randomized trials may be designed and interpreted as single experiments or they may be seen in the context of other similar or relevant evidence. The amount and complexity of available randomized evidence vary for different topics. Systematic reviews may be useful in identifying gaps in the existing randomized evidence, pointing to discrepancies between trials, and planning future trials. A new, promising, but also very much debated extension of systematic reviews, mixed treatment comparison (MTC) meta-analysis, has become increasingly popular recently. MTC meta-analysis may have value in interpreting the available randomized evidence from networks of trials and can rank many different treatments, going beyond focusing on simple pairwise-comparisons. Nevertheless, the evaluation of networks also presents special challenges and caveats. In this article, we review the statistical methodology for MTC meta-analysis. We discuss the concept of inconsistency and methods that have been proposed to evaluate it as well as the methodological gaps that remain. We introduce the concepts of network geometry and asymmetry, and propose metrics for the evaluation of the asymmetry. Finally, we discuss the implications of inconsistency, network geometry and asymmetry in informing the planning of future trials.

Factors associated with findings of published trials of drug-drug comparisons: why some statins appear more efficacious than others

BACKGROUND

Published pharmaceutical industry-sponsored trials are more likely than non-industry-sponsored trials to report results and conclusions that favor drug over placebo. Little is known about potential biases in drug-drug comparisons. This study examined associations between research funding source, study design characteristics aimed at reducing bias, and other factors that potentially influence results and conclusions in randomized controlled trials (RCTs) of statin-drug comparisons.

METHODS AND FINDINGS

This is a cross-sectional study of 192 published RCTs comparing a statin drug to another statin drug or non-statin drug. Data on concealment of allocation, selection bias, blinding, sample size, disclosed funding source, financial ties of authors, results for primary outcomes, and author conclusions were extracted by two coders (weighted kappa 0.80 to 0.97). Univariate and multivariate logistic regression identified associations between independent variables and favorable results and conclusions. Of the RCTs, 50% (95/192) were funded by industry, and 37% (70/192) did not disclose any funding source. Looking at the totality of available evidence, we found that almost all studies (98%, 189/192) used only surrogate outcome measures. Moreover, study design weaknesses common to published statin-drug comparisons included inadequate blinding, lack of concealment of allocation, poor follow-up, and lack of intention-to-treat analyses. In multivariate analysis of the full sample, trials with adequate blinding were less likely to report results favoring the test drug, and sample size was associated with favorable conclusions when controlling for other factors. In multivariate analysis of industry-funded RCTs, funding from the test drug company was associated with results (odds ratio = 20.16 [95% confidence interval 4.37-92.98], p < 0.001) and conclusions (odds ratio = 34.55 [95% confidence interval 7.09-168.4], p < 0.001) that favor the test drug when controlling for other factors. Studies with adequate blinding were less likely to report statistically significant results favoring the test drug.

CONCLUSIONS

RCTs of head-to-head comparisons of statins with other drugs are more likely to report results and conclusions favoring the sponsor's product compared to the comparator drug. This bias in drug-drug comparison trials should be considered when making decisions regarding drug choice.

Effects of different chemotherapy regimens on survival for advanced cervical cancer: Systematic review and meta-analysis

BACKGROUND

A large number of trials have assessed various chemotherapy regimens for the treatment of advanced cervical cancer, but there is uncertainty about the magnitude of survival benefits.

METHODS

We searched (last update January 2006) for trials in women with locally advanced or disseminated cervical cancer that compared neo-adjuvant or concurrent chemotherapy plus radiotherapy versus radiotherapy alone; or different chemotherapy regimens among themselves (with or without background radiotherapy in both arms). Sixty-five trials were identified with survival data on 11,180 women. Results for survival were combined with fixed and random effects models and between-study heterogeneity was estimated. Separate results were obtained for different regimens, cycle length, and type of chemotherapy (neo-adjuvant, concurrent, without radiotherapy).

RESULTS

Twenty two comparisons had survival data on 3837 women randomized to receive chemotherapy plus radiotherapy versus radiotherapy alone; the summary relative hazard for mortality was 0.95, 95% CI, 0.83-1.08. Modest between-study heterogeneity (I2=38%) seemed to be due to contradictory results in early trials; trials published in the last decade had a summary relative hazard 0.89 (95% CI, 0.78-1.02) and no between-study heterogeneity (I2=0%). Results were similar for neo-adjuvant chemotherapy and for concurrent chemo-radiotherapy. Cisplatin or cisplatin-based combinations had no significant benefit overall, but a potential benefit was seen with short-length cycles (14 days) and a marginally significant harm with longer-length cycles (summary relative hazards 0.80, 95% CI, 0.66-0.99 and 1.18, 95% CI, 1.02-1.38, respectively). The summary relative hazard was 1.02, (95% CI, 0.84-1.24) for trials using neo-adjuvant chemotherapy and 0.85 (95% CI, 0.73-1.00) for trials using concurrent chemotherapy.

CONCLUSIONS

Evidence on chemotherapy in women with advanced cervical cancer is not encouraging for major survival benefits. However, small benefits have been observed in some trials, especially with short-length cycles of cisplatin-based regimens and concurrent chemotherapy and radiotherapy.

Evolution and translation of research findings: from bench to where?

The credibility and replication of research findings evolve over time, as data accumulate. However, translation of postulated research promises to real-life biomedical applications is uncommon. In some fields of research, we may observe diminishing effects for the strength of research findings and rapid alternations of exaggerated claims and extreme contradictions--the "Proteus Phenomenon." While these phenomena are probably more prominent in the basic sciences, similar manifestations have been documented even in clinical trials and they may undermine the credibility of clinical research. Significance-chasing bias may be in part responsible, but the greatest threat may come from the poor relevance and scientific rationale and thus low pre-study odds of success of research efforts. Given that we currently have too many research findings, often with low credibility, replication and rigorous evaluation become as important as or even more important than discovery. Credibility, replication, and translation are all desirable properties of research findings, but are only modestly correlated. In this essay, I discuss some of the evidence (or lack thereof) for the process of evolution and translation of research findings, with emphasis on the biomedical sciences.

Randomized evidence on chemotherapy and hormonal therapy regimens for advanced endometrial cancer: An overview of survival data

Several chemotherapy and hormonal therapy regimens have been used in advanced endometrial cancer. In this review we have systematically evaluated the available data from randomized trials on survival. We searched MEDLINE, EMBASE and the Cochrane Library (last search April 2005) for randomized controlled trials evaluating various chemotherapy or hormonal therapy regimens in locally advanced or metastatic endometrial cancer. We focused on survival outcomes and examined trial characteristics pertaining to quality and potential biases. Across 17 eligible trials (2964 patients randomized), only 4 regimens were involved in more than one trial, and only two trials had used the same comparison of regimens. A statistically significant effect in survival was seen only in one recent trial, but it was borderline (P = 0.032) and amounted to only 3 months difference in median survival. Three more trials reported some survival benefits, but these were seen only after specific adjustments, and the difference was against the experimental arm in one of these three trials. Only four trials (24%) apparently analyzed all randomized patients and none of the trials were blinded. Median survival was seemingly longer in more recent compared with older trials, but this effect was driven by the inclusion of significantly fewer patients with poor performance status in more recent trials (P < 0.001). Overall, randomized evidence on systemic treatment in advanced endometrial cancer is fragmented and survival benefits for specific regimens are questionable.

Local literature bias in genetic epidemiology: an empirical evaluation of the Chinese literature

BACKGROUND

Postulated epidemiological associations are subject to several biases. We evaluated whether the Chinese literature on human genome epidemiology may offer insights on the operation of selective reporting and language biases.

METHODS AND FINDINGS

We targeted 13 gene-disease associations, each already assessed by meta-analyses, including at least 15 non-Chinese studies. We searched the Chinese Journal Full-Text Database for additional Chinese studies on the same topics. We identified 161 Chinese studies on 12 of these gene-disease associations; only 20 were PubMed-indexed (seven English full-text). Many studies (14-35 per topic) were available for six topics, covering diseases common in China. With one exception, the first Chinese study appeared with a time lag (2-21 y) after the first non-Chinese study on the topic. Chinese studies showed significantly more prominent genetic effects than non-Chinese studies, and 48% were statistically significant per se, despite their smaller sample size (median sample size 146 versus 268, p < 0.001). The largest genetic effects were often seen in PubMed-indexed Chinese studies (65% statistically significant per se). Non-Chinese studies of Asian-descent populations (27% significant per se) also tended to show somewhat more prominent genetic effects than studies of non-Asian descent (17% significant per se).

CONCLUSION

Our data provide evidence for the interplay of selective reporting and language biases in human genome epidemiology. These biases may not be limited to the Chinese literature and point to the need for a global, transparent, comprehensive outlook in molecular population genetics and epidemiologic studies in general.

Methods to assess intended effects of drug treatment in observational studies are reviewed

BACKGROUND AND OBJECTIVE

To review methods that seek to adjust for confounding in observational studies when assessing intended drug effects.

METHODS

We reviewed the statistical, economical and medical literature on the development, comparison and use of methods adjusting for confounding.

RESULTS

In addition to standard statistical techniques of (logistic) regression and Cox proportional hazards regression, alternative methods have been proposed to adjust for confounding in observational studies. A first group of methods focus on the main problem of nonrandomization by balancing treatment groups on observed covariates: selection, matching, stratification, multivariate confounder score, and propensity score methods, of which the latter can be combined with stratification or various matching methods. Another group of methods look for variables to be used like randomization in order to adjust also for unobserved covariates: instrumental variable methods, two-stage least squares, and grouped-treatment approach. Identifying these variables is difficult, however, and assumptions are strong. Sensitivity analyses are useful tools in assessing the robustness and plausibility of the estimated treatment effects to variations in assumptions about unmeasured confounders.

CONCLUSION

In most studies regression-like techniques are routinely used for adjustment for confounding, although alternative methods are available. More complete empirical evaluations comparing these methods in different situations are needed.