Ten traps for the unwary in surgical series

Ten traps for the unwary in surgical series: A case study in mesothelioma reportsTom Treasure, MDa,*, Martin Utley, PhDb a Department of Cardiothoracic Surgery, Guy’s Hospital, London, United Kingdomb Clinical Operational Research Unit, University College London, London, United Kingdom.

Received for publication October 31, 2006; revisions received January 31, 2007; accepted for publication February 12, 2007.

* Address for reprints: Tom Treasure, Professor of Cardiothoracic Surgery, Guy’s Hospital, London, United Kingdom. (Email: tom.treasure@gmail.com).

Case series are the commonest form of evidence in cancer surgery, an area of practice for which there are few randomized trials. There are pitfalls in the presentation and interpretation of this clinical material, and in this article we highlight a number of them. We have used as a case study the body of literature concerning resection of mesothelioma. Mesothelioma is a disease that concerns us greatly in Europe because we are facing an epidemic that will peak between 2010 and 2015,1 and an even greater burden of disease will follow in parts of the developing world. It is a grim cancer, and the quality of evidence is poor.2 However, the need to understand the limitations of case series spreads much wider than mesothelioma.

Authors may recognize their work in the examples we present, and so we may well cause offence. This is not our intention. Readers may be tempted to search our own work for examples of errors, and they will find them—more egregious than any of these. The alternative to citing real instances was for us to make them up or make them anonymous. However, then maybe some would say, "Surely no one would do that?" so they had to be real. We did not search systematically for examples; they come from articles we know through our research in mesothelioma. Finally, we have not shied away from using prominent examples, from leading authors, in leading journals. We needed to cite the best work or our concerns could be discounted as the result of a pedant’s trawl of the world’s literature. They are quoted with respect for the authors and editors, who we know have broad shoulders.