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Meta-Analysis as a Symptom: The Example of Flow Diverters

Meta-Analysis as a Symptom: The Example of Flow Diverters LETTERS he principle of a meta-analysis is to evaluate the effect of a When a treatment has convinced a discipline of its efficacy and Ttreatment by combining the results of several studies. This relative safety, meta-analyses are not necessary. There is no meta- method increases the statistical power to test certain hypotheses, analysis concerning usefulness of antibiotic treatment in pulmo- especially when several randomized controlled trials are each too nary tuberculosis. small to provide an answer or have provided contradictory This overabundance of meta-analyses expresses the desire to conclusions. convince physicians and patients of the benefits of this implant. Because we have very few randomized trials in interventi- Quantity makes quality. Most meta-analyses (as well as most case onal neuroradiology, our meta-analyses most often collect data of series) on flow diversion report a cumulative morbidity/mortality uncontrolled case series. A meta-analysis then makes sense when rate of 10% or so, as if this was the normal price to pay for “other- the target pathology is rare, with a limited number of cases wise untreatable” aneurysms. The argument that flow diversion reported in each publication. However, in this case, a single should fill a therapeutic void is not supported by the number of meta-analysis is sufficient, even if it may need to be updated units used between 2 interventional neuroradiologist centers that sometimes. treat roughly the same number of aneurysms per year. The regu- The excessive use of multiple meta-analyses for the same med- latory status of implants allows them to be used in indications dif- ical problem is a symptom: the hope that the next one will pro- ferent from those for which they were initially presented to the vide better results than the previous one. Any neuroradiologist health authorities (at least in Europe). Thus, large and giant can consult PubMed and enter the term, object of his or her aneurysms of the carotid siphon, the initial indication for flow research, followed by “AND meta-analysis” and compare the diverters, are now only an excuse to extend their use in the treat- number of responses obtained. Between February 2013 and ment of small or even very small aneurysms in multiple other January 2020, 19 meta-analyses, often redundant, have been pub- locations, and to “accept” the 10% complication rate without bal- lished concerning the treatment of cerebral aneurysms by flow ancing this risk with the one of other management options, diverters. It is at this point that it would become possible to envis- including observation. The apparent aim of multiplying meta- age a meta-analysis of meta-analyses! analyses may finally be to replace the unquestionable methodo- I know that not all cerebral aneurysms are the same and that logic evaluation, ie, the randomized controlled trial. it may be necessary to distinguish those of the carotid from those The financial crisis to which our insurance systems are subject of the vertebrobasilar circulation, to separately examine large and will probably force health authorities to no longer offer reim- small aneurysms, those of the anterior communicating artery and bursement for expensive devices if they have not been subjected those of the middle cerebral artery, those treatments for which to rigorous evaluation. While a waiting that, we can bet that we one antiplatelet has been prescribed rather than another, and so will still have the opportunity to read a new meta-analysis about forth. However, all these remarks also apply to coil treatment, flow diverters in the near future. and there have been only 2 published meta-analyses on that topic in the 27 years that they have been in clinical use. Why is that? E. Houdart Service de Neuroradiologie Hôpital Lariboisière Paris, France http://dx.doi.org/10.3174/ajnr.A6594 AJNR Am J Neuroradiol 41:E51 Jul 2020 www.ajnr.org E51 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png American Journal of Neuroradiology American Journal of Neuroradiology

Meta-Analysis as a Symptom: The Example of Flow Diverters

Houdart, E.
American Journal of Neuroradiology , Volume 41 (7) – Jul 1, 2020
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American Journal of Neuroradiology
Copyright
© 2020 by American Journal of Neuroradiology
ISSN
0195-6108
eISSN
1936-959X
DOI
10.3174/ajnr.A6594
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Abstract

LETTERS he principle of a meta-analysis is to evaluate the effect of a When a treatment has convinced a discipline of its efficacy and Ttreatment by combining the results of several studies. This relative safety, meta-analyses are not necessary. There is no meta- method increases the statistical power to test certain hypotheses, analysis concerning usefulness of antibiotic treatment in pulmo- especially when several randomized controlled trials are each too nary tuberculosis. small to provide an answer or have provided contradictory This overabundance of meta-analyses expresses the desire to conclusions. convince physicians and patients of the benefits of this implant. Because we have very few randomized trials in interventi- Quantity makes quality. Most meta-analyses (as well as most case onal neuroradiology, our meta-analyses most often collect data of series) on flow diversion report a cumulative morbidity/mortality uncontrolled case series. A meta-analysis then makes sense when rate of 10% or so, as if this was the normal price to pay for “other- the target pathology is rare, with a limited number of cases wise untreatable” aneurysms. The argument that flow diversion reported in each publication. However, in this case, a single should fill a therapeutic void is not supported by the number of meta-analysis is sufficient, even if it may need to be updated units used between 2 interventional neuroradiologist centers that sometimes. treat roughly the same number of aneurysms per year. The regu- The excessive use of multiple meta-analyses for the same med- latory status of implants allows them to be used in indications dif- ical problem is a symptom: the hope that the next one will pro- ferent from those for which they were initially presented to the vide better results than the previous one. Any neuroradiologist health authorities (at least in Europe). Thus, large and giant can consult PubMed and enter the term, object of his or her aneurysms of the carotid siphon, the initial indication for flow research, followed by “AND meta-analysis” and compare the diverters, are now only an excuse to extend their use in the treat- number of responses obtained. Between February 2013 and ment of small or even very small aneurysms in multiple other January 2020, 19 meta-analyses, often redundant, have been pub- locations, and to “accept” the 10% complication rate without bal- lished concerning the treatment of cerebral aneurysms by flow ancing this risk with the one of other management options, diverters. It is at this point that it would become possible to envis- including observation. The apparent aim of multiplying meta- age a meta-analysis of meta-analyses! analyses may finally be to replace the unquestionable methodo- I know that not all cerebral aneurysms are the same and that logic evaluation, ie, the randomized controlled trial. it may be necessary to distinguish those of the carotid from those The financial crisis to which our insurance systems are subject of the vertebrobasilar circulation, to separately examine large and will probably force health authorities to no longer offer reim- small aneurysms, those of the anterior communicating artery and bursement for expensive devices if they have not been subjected those of the middle cerebral artery, those treatments for which to rigorous evaluation. While a waiting that, we can bet that we one antiplatelet has been prescribed rather than another, and so will still have the opportunity to read a new meta-analysis about forth. However, all these remarks also apply to coil treatment, flow diverters in the near future. and there have been only 2 published meta-analyses on that topic in the 27 years that they have been in clinical use. Why is that? E. Houdart Service de Neuroradiologie Hôpital Lariboisière Paris, France http://dx.doi.org/10.3174/ajnr.A6594 AJNR Am J Neuroradiol 41:E51 Jul 2020 www.ajnr.org E51

Journal

American Journal of Neuroradiology – American Journal of Neuroradiology

Published: Jul 1, 2020

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