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The quality of research synthesis in surgery: the case of laparoscopic surgery for colorectal cancer.

Martel G, Duhaime S, Barkun JS, Boushey RP, Ramsay CR, Fergusson DA - Syst Rev (2012)

Bottom Line: Reviews were synthesized, and outcomes were compared qualitatively.Overall survival was evaluated by ten reviews, none of which found a significant difference.Further systematic reviews or meta-analyses are unlikely to be justified without specifying a significantly different research objective.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Surgery, Department of Epidemiology & Community Medicine, and Ottawa Hospital Research Institute, The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada. guillaume.martel@gmail.com

ABSTRACT

Background: Several systematic reviews and meta-analyses populate the literature on the effectiveness of laparoscopic surgery for colorectal cancer. The utility of this body of work is unclear. The objective of this study was to synthesize all such systematic reviews in terms of clinical effectiveness, to appraise their quality, and to determine whether areas of duplication exist across reviews.

Methods: Systematic reviews comparing laparoscopic and open surgery for colorectal cancer were identified using a comprehensive search protocol (1991 to 2008). The primary outcome was overall survival. The methodological quality of reviews was appraised using the Assessment of Multiple Systematic Reviews (AMSTAR) instrument. Abstraction and quality appraisal was carried out by two independent reviewers. Reviews were synthesized, and outcomes were compared qualitatively. A citation analysis was carried out using simple matrices to assess the comprehensiveness of each review.

Results: In total, 27 reviews were included; 13 reviews included only randomized controlled trials. Rectal cancer was addressed exclusively by four reviews. There was significant overlap between review purposes, populations and, outcomes. The mean AMSTAR score (out of 11) was 5.8 (95% CI: 4.6 to 7.0). Overall survival was evaluated by ten reviews, none of which found a significant difference. Three reviews provided a selective meta-analysis of time-to-event data. Previously published systematic reviews were poorly and highly selectively referenced (mean citation ratio 0.16, 95% CI: 0.093 to 0.22). Previously published trials were not comprehensively identified and cited (mean citation ratio 0.56, 95% CI: 0.46 to 0.65).

Conclusions: Numerous overlapping systematic reviews of laparoscopic and open surgery for colorectal cancer exist in the literature. Despite variable methods and quality, survival outcomes are congruent across reviews. A duplication of research efforts appears to exist in the literature. Further systematic reviews or meta-analyses are unlikely to be justified without specifying a significantly different research objective. This works lends support to the registration and updating of systematic reviews.

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Synthesis of overall survival across systematic reviews.
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Figure 4: Synthesis of overall survival across systematic reviews.

Mentions: The primary outcome of overall survival was pooled quantitatively in ten reviews (Figure 4 and Additional file 2). Most authors presented this data as a dichotomous outcome (alive/dead) at maximum follow-up. After meta-analysis, this data was presented as odds ratios (OR), risk ratios (RR), and Stouffer's composite Z (ZC). Two groups presented this outcome as time-to-event data by pooling hazard ratios (HR), using methods relying on the estimation of HR from Kaplan-Meier curves. Finally, another group also presented a HR that was derived from an individual patient data meta-analysis. No significant difference in overall survival was found between laparoscopic and open surgery for colorectal cancer across all meta-analytic comparisons. The direction of effect for all analyses favored laparoscopy, except for two which were conducted on observational studies and using a subset of studies with independent patient data [18,34].


The quality of research synthesis in surgery: the case of laparoscopic surgery for colorectal cancer.

Martel G, Duhaime S, Barkun JS, Boushey RP, Ramsay CR, Fergusson DA - Syst Rev (2012)

Synthesis of overall survival across systematic reviews.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351744&req=5

Figure 4: Synthesis of overall survival across systematic reviews.
Mentions: The primary outcome of overall survival was pooled quantitatively in ten reviews (Figure 4 and Additional file 2). Most authors presented this data as a dichotomous outcome (alive/dead) at maximum follow-up. After meta-analysis, this data was presented as odds ratios (OR), risk ratios (RR), and Stouffer's composite Z (ZC). Two groups presented this outcome as time-to-event data by pooling hazard ratios (HR), using methods relying on the estimation of HR from Kaplan-Meier curves. Finally, another group also presented a HR that was derived from an individual patient data meta-analysis. No significant difference in overall survival was found between laparoscopic and open surgery for colorectal cancer across all meta-analytic comparisons. The direction of effect for all analyses favored laparoscopy, except for two which were conducted on observational studies and using a subset of studies with independent patient data [18,34].

Bottom Line: Reviews were synthesized, and outcomes were compared qualitatively.Overall survival was evaluated by ten reviews, none of which found a significant difference.Further systematic reviews or meta-analyses are unlikely to be justified without specifying a significantly different research objective.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Surgery, Department of Epidemiology & Community Medicine, and Ottawa Hospital Research Institute, The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada. guillaume.martel@gmail.com

ABSTRACT

Background: Several systematic reviews and meta-analyses populate the literature on the effectiveness of laparoscopic surgery for colorectal cancer. The utility of this body of work is unclear. The objective of this study was to synthesize all such systematic reviews in terms of clinical effectiveness, to appraise their quality, and to determine whether areas of duplication exist across reviews.

Methods: Systematic reviews comparing laparoscopic and open surgery for colorectal cancer were identified using a comprehensive search protocol (1991 to 2008). The primary outcome was overall survival. The methodological quality of reviews was appraised using the Assessment of Multiple Systematic Reviews (AMSTAR) instrument. Abstraction and quality appraisal was carried out by two independent reviewers. Reviews were synthesized, and outcomes were compared qualitatively. A citation analysis was carried out using simple matrices to assess the comprehensiveness of each review.

Results: In total, 27 reviews were included; 13 reviews included only randomized controlled trials. Rectal cancer was addressed exclusively by four reviews. There was significant overlap between review purposes, populations and, outcomes. The mean AMSTAR score (out of 11) was 5.8 (95% CI: 4.6 to 7.0). Overall survival was evaluated by ten reviews, none of which found a significant difference. Three reviews provided a selective meta-analysis of time-to-event data. Previously published systematic reviews were poorly and highly selectively referenced (mean citation ratio 0.16, 95% CI: 0.093 to 0.22). Previously published trials were not comprehensively identified and cited (mean citation ratio 0.56, 95% CI: 0.46 to 0.65).

Conclusions: Numerous overlapping systematic reviews of laparoscopic and open surgery for colorectal cancer exist in the literature. Despite variable methods and quality, survival outcomes are congruent across reviews. A duplication of research efforts appears to exist in the literature. Further systematic reviews or meta-analyses are unlikely to be justified without specifying a significantly different research objective. This works lends support to the registration and updating of systematic reviews.

Show MeSH
Related in: MedlinePlus