Clinical research is wasted when systematic reviews fail to provide a complete and up-to-date evidence synthesis
An innovative analysis showed that systematic reviews of second-line treatments of advanced non-small cell lung cancer provide a fragmented, out-of-date panorama of the evidence for all treatments. These findings question the current approach to synthesize evidence.
The article in BMC Medicine is co-authored by Perrine Créquit, Ludovic Trinquart, Amélie Yavchitz, and Philippe Ravaud, from Cochrane France and INSERM U1153 METHODS team, Paris, France.
Multiple treatments are now frequently available for the same disease. Patients and physicians need a comprehensive, up-to-date synthesis of evidence for all competing treatments to know which treatments work best. For example, patients and physicians are eager to have a complete synthesis on second-line treatments of advanced non-small cell lung cancer. On this example, the authors aimed to assess if such a complete and up-to-date evidence synthesis was available over time.
They performed a series of systematic overviews and networks of randomized trials to assess the gap between evidence covered by systematic reviews and available trials of second-line treatments for advanced non-small cell lung cancer. They performed an exhaustive search to identify all the evidence, by querying a broad range of sources sequentially by year from 2009 to March 2, 2015. Then, they sequentially compared the amount of evidence missing from systematic reviews to the randomized evidence available for inclusion in systematic reviews each year.
The researchers identified 77 trials (28,636 patients) assessing 47 treatments with 54 direct comparisons between treatments. They also found 29 systematic reviews, 13 published after 2013. However, whole segments of evidence were left behind. From 2009 to 2015, the evidence covered by existing systematic reviews was consistently incomplete: 45 % to 70 % of trials; 30 % to 58 % of patients; 40 % to 66 % of treatments; and 38 % to 71 % of comparisons between treatments were missing.
To tackle this considerable issue, the authors propose a new approach to evidence synthesis, called “live cumulative network meta-analysis”. They describe how to switch from a series of systematic reviews – performed at different points in time, frequently out-of-date, and focusing on specific treatments (many treatments being not considered) – to a single systematic reviews covering all treatments, with network meta-analyses, and updated continuously to incorporate the results of new trials when they become available.