MCC 2011 - Slide 24

Systematic review and meta-analysis NNT NNH, setting up a protocol Theo Wiggers Cascais, February 16 th ,2011

We used for a Critical Appraisal of
the Literature:
“ two cohort studies, one prospective trial and one Cochrane study”
and we call it a systematic analysis

This lecture
Systematic review and meta-analysis
Number needed to treat Number needed to harm
Making a protocol

The meaning of the name ? Professor Archibald Leman Cochrane (1909 - 1988) Director of the new Medical Research council’s Epidemiology Research Unit, Cardiff

Collaboration
Building on the enthusiasm of individuals
Avoiding duplication
Minimizing bias
Keeping up to date
Striving for relevance
Promoting access
Ensuring quality
Continuity
Enabling wide participation
The Principles of The Cochrane Collaboration

Number of reviews

"Every day someone, somewhere searches The Cochrane Library every second , reads an abstract every two seconds and downloads a full-text article every three seconds." - The Cochrane Library usage data 2009
Impact Factor 2008: The Cochrane Database of Systematic Reviews has an Impact Factor OF 5.182 and is ranked 12th out of 107 in the ISI category Medicine, General & Internal
The Cochrane Library

The Cochrane Library
The Cochrane Database of Systematic Reviews ( CDSR ) contains the full text (including methods, results and conclusions) for Cochrane reviews and protocols.
The Database of Abstracts of Reviews of Effects ( DARE ), assembled and maintained by the Centre for Reviews and Dissemination in York, UK, contains critical assessments and structured abstracts of other systematic reviews, conforming to explicit quality criteria.
The Cochrane Central Register of Controlled Trials ( CENTRAL ) contains bibliographic information on hundreds of thousands of studies, including those published in conference proceedings and many other sources not currently listed in other bibliographic databases.
The Cochrane Methodology Register ( CMR ) contains bibliographic information on articles and books on the science of reviewing research, and a prospective register of methodological studies.
The Cochrane Collaboration section contains contact details and other information about CRGs and the other contributing groups within The Cochrane Collaboration.

52 collaborative review groups http://www.cochrane-net.org/openlearning Cochrane Colorectal Cancer Group www.cccg.cochrane.org

Colorectal, anal, and small bowel cancer
Benign proctological diseases, peritoneal diseases, and surgical treatment for inflammatory bowel diseases
Surgical anal diseases
Abdominal hernias
Appendiceal diseases
Diverticulitis
Peritonitis
Cochrane Colorectal Cancer Group

Co-ordinating editor: Peer Wille-Jørgensen, Denmark
Deputy co-ordinating editor: Richard Nelson, USA
11 Editors 600 reviewers 150 External Peer Referees
171 protocols and reviews
Neoplastic diseases of the small bowel 9
Neoplastic diseases of the colon 57
Neoplastic diseases of the rectum and anus 51
Cochrane Colorectal Cancer Group

Types of people (participants)
Types of comparison (intervention)
Types of outcome
The three key components of a question for a systematic review Start with the preparation of a protocol followed by a review

Medline 30-80% of published RCTs
Embase
Cochrane Central Register Controlled Trials
Handsearching, conference proceedings
Other sources
Search strategies

Cover sheet
Synopsis
Abstract
Text: introduction (background and objective), materials (selection criteria search strategy) and methods, results (description of studies, methodological quality , results), discussion, reviewers’ conclusions
Tables and figures
References
Components a systematic review

Quality assessment of the study in order to limit bias:
selection bias (intervention vs control)
performance bias (exposure to intervention)
attrition bias (withdrawals during follow-up)
detection bias (outcome)
Rating validity A, B, C (unlikely, raises doubt, seriously weakens)
What does allocation concealment mean?

Pooled analysis of enough qualified studies
RevMan
When do we perform a meta-analysis ?

Forest plot

Do we always need a Randomized Controlled Trial? and a subsequent meta-analysis

Do we always need a Randomized Controlled Trial? Hazardous journeys Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials Gordon C S Smith, Jill P Pell BMJ VOLUME 327 20–27 DECEMBER 2003 Update 2006 next update to be expected?? We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute .

Do we always need a Randomized Controlled Trial? Prospective cohort studies preferable as part of a national audit program can bring strong and valid proof. For example in the Nordic audit report the same reduction of local recurrences after TME and 5x5 Gray are observed as in the Dutch and UK study

Number Needed to Treat
NNT= absolute risk reduction :number of patients necessary to show a reduction of an event
Example: 5% less local recurrences
NNT= 20
Relative risk reduction: percentage of reduction of risk
Example: reduction from 10-5%= 50% risk reduction
If from 1 to 0,5%
NNT 200
Relative risk reduction= 50 %

Number Needed to Harm
NNH= how many patients need to be exposed to a risk factor over a specific period to cause harm in one patient that would not otherwise have been harmed
Example
NNH=10 (if 100 individuals are exposed to the risk factor, 10 will develop the complication that would not have otherwise)
Incidence of incontinence Radiotherapy 50% Surgery 40%

Making a protocol(1)
Title
Background
Endpoint
Primary endpoint
Secondary endpoint(s)
Study design
Selection criteria
Criteria for inclusion
Criteria for exclusion

Making a protocol(2)
Criteria for inclusion
Criteria for exclusion
Baseline screening
Stratification
Treatment arms
Statistical considerations
Expected percentage in control arm
Improvement in experimental arm
Planned sample size

Thank you for your attention

MCC 2011 - Slide 24

by European School of Oncology

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MCC 2011 - Slide 24 Presentation Transcript

MCC 2011 - Slide 24

by European School of Oncology

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MCC 2011 - Slide 24 Presentation Transcript

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