Current controversies in the application of meta—analysis, (with special reference to oncological treatments)

Meta–analysis was proposed more than 20 years ago as an innovative technique for pooling the results of a series of clinical studies. This technique has a two–fold purpose: i) to retrieve pertinent clinical information without introducing selection biases; ii) to combine these clinical data obtained from different sources into a single synthetic index that summarises all available information. This review highlights the current perspectives in the application of meta–analysis and places particular emphasis on discussing the limitations of this technique that have been identified in recent years. Specific controversies in this area include: i) comparison between meta–analysis of the literature and meta–analysis of individual patient data; ii) heterogeneity of the clinical material introduced in the meta–analytic pooling; and iii) survival meta–analysis as a method for pooling long–term outcome data. After debating these three controversial points, this review examines the newest uses of meta–analysis that have been proposed for the evaluation of cost–effectiveness data and tries to identify the meta–analytic applications that will probably be expanded in the near future as opposed to those that will instead be developed less and less.