International Oncology Subject Guide: Systematic Review

What is a systematic review?

A systematic review is a type of literature review that collects, selects, critically analyzes, extracts data, and synthesizes the results of studies asking similar questions. It is designed to provide a complete and exhaustive summary of current literature relevant to a research question. Systematic reviews of randomized controlled trials are key in the practice of evidence-based medicine, and they are conducted in an unbiased, reproducible way to provide evidence for practice and policy-making and identify gaps in research. Meta-analysis is a systematic review that use statistical techniques to combine results from two or more separate studies. 

Teamwork:
Systematic Reviews are usually a team effort. Important areas of expertise to cover are;

• Content experts - It is important to have team members or an active consultant to provide expertise in the area covered by the review. Input is usually needed from practitioners and researchers representing a variety of perspectives.
• Systematic Reviews methods experts - One or more persons with expertise in the methods of conducting Systematic Reviews is needed. This person may be responsible for developing the procedures and documentation standards for the review. A Systematic Review methods expert may also be a content expert, but more than one investigator-level reviewer is necessary since some steps in the process require dual review or data checking that requires expertise in research and statistical methodology.
• Statistician - If meta-analysis is to be considered, access to a statistician with experience in meta-analysis is needed.
• Information Specialist/ Librarian - Database searching requires specialized knowledge that general research training does not provide. Preferably, the information specialist/ librarian searcher has experience with the extensive searching and documentation procedures that are a part of a systematic review.

O'Connor, E., Whitlock, E., & Spring, B. (2007). Introduction to Systematic Reviews, 

Prior to embarking on a systematic review:

•  Investigate whether there are existing reviews on the topic, identify the gaps in the studies and prevent duplicating the previous reviews.
• Develop a detailed protocol to describe the rationale, hypothesis, planned methods of the review, made publicly available, and register in a registry, such as PROSPERO, Open Science Framework. 

Steps in a systematic review:

1. Define a structured research question, and eligibility criteria: specify study characteristics (e.g., PICOS, length of follow-up) and report characteristics (e.g., years considered, language, publication status) used as criteria for eligibility, giving rationale. 
2. Develop a search strategy to retrieve published studies relating to that question: perform a comprehensive literature search using controlled vocabulary and relevant keywords in multiple databases including any limits used to identify all published relevant studies, and present at least one of the searches such that it could be repeated.
3. Apply inclusion and exclusion criteria: state the process for selecting studies (i.e., screening, eligibility, included in the systematic review, and, if applicable, included in the meta-analysis).
4. Perform data collection/extraction: describe the method of data extraction form reports (e.g., piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators. 
5. Conduct a quality appraisal of included studies: describe methods used for assessing the risk of bias of individual studies (including specification of whether this was done at the study or outcome level), and how this information is to be used in any data synthesis. 
6. Data analysis (narrative or quantitative): analysis may be narrative, such as a structured summary and discussion of the studies’ characteristics and findings, or quantitative, that is involving statistical analysis (meta-analysis).

7. Assess, interpret, and summarize results: summarize findings, present detailed methodology (search strategies used, inclusion/exclusion criteria, etc.) such that the review can be reproducible. Provide a general interpretation of the results in the context of other evidence, and implications for future research to fill existing gaps in knowledge or to strengthen the body of evidence. Perform a meta-analysis if the studies allow.

Reporting and documenting the systematic review process:

There are a number of reporting standards for systematic reviews. These can serve as guidelines for protocol, manuscript preparation, and journals may require.

Mathilde Johansen and Simon Francis Thomsen, “Guidelines for Reporting Medical Research: A Critical Appraisal,” International Scholarly Research Notices, vol. 2016, Article ID 1346026, 7 pages, 2016. https://doi.org/10.1155/2016/1346026.

Data management:

Citation management software helps manage and organize the citations from various sources, and format bibliography using different type of styles, such as, Vancouver, APA, journal specified citation style. 

Systematic review software:​

Here are select software and web-based tools that are helpful for managing systematic reviews. Please check before downloading any software, as this is subject to change.

Data collection (Coding):

Data collection is the process of gathering and measuring information on targeted variables in an established systematic fashion, which then enables one to answer relevant questions and evaluate outcomes. Here is a list of some free online tools: 

Meta-analysis tools:
Meta-analysis  is a subset of systematic reviews; a method for systematically combining pertinent qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power. "Meta-analysis should only be considered when a group of studies is sufficiently homogeneous in terms of participants, interventions and outcomes to provide a meaningful summary.  It is often appropriate to take a broader perspective in a meta-analysis than in a single clinical trial. A common analogy is that systematic reviews bring together apples and oranges, and that combining these can yield a meaningless result. This is true if apples and oranges are of intrinsic interest on their own, but may not be if they are used to contribute to a wider question about fruit. For example, a meta-analysis may reasonably evaluate the average effect of a class of drugs by combining results from trials where each evaluates the effect of a different drug from the class." Below are some selected meta-analysis tools to help to develop summary statistics obtained from a series of related studies.

How to prepare a manuscript for international journals:

When you organize your manuscript, the first thing to consider is that the order of sections will be very different than the order of items on your checklist. An article begins with the Title, Abstract and Keywords. The article text follows the IMRAD format, which responds to the questions below:

• Introduction: What did you/others do? Why did you do it? 
• Methods: How did you do it? 
• Results: What did you find?
• And
• Discussion: What does it all mean?

The main text is followed by the Conclusion, Acknowledgements, References and Supporting Materials.