title: On meta-analytic assessment of surrogate outcomes.
abstract: We discuss the strengths and weaknesses of the meta-analytic approach to estimating the effect of a new treatment on a true clinical outcome measure, T, from the effect of treatment on a surrogate response, S. The meta-analytic approach (see Daniels and Hughes (1997) 16, 1965-1982) uses data from a series of previous studies of interventions similar to the new treatment. The data are used to estimate relationships between summary measures of treatment effects on T and S that can be used to infer the magnitude of the effect of the new treatment on T from its effects on S. We extend the class of models to cover a broad range of applications in which the parameters define features of the marginal distribution of (T, S). We present a new bootstrap procedure to allow for the variability in estimating the distribution that governs the between-study variation. Ignoring this variability can lead to confidence intervals that are much too narrow. The meta-analytic approach relies on quite different data and assumptions than procedures that depend, for example, on the conditional independence, at the individual level, of treatment and T, given S (see Prentice (1989) 8, 431-440). Meta-analytic calculations in this paper can be used to determine whether a new study, based only on S, will yield estimates of the treatment effect on T that are precise enough to be useful. Compared to direct measurement on T, the meta-analytic approach has a number of limitations, including likely serious loss of precision and difficulties in defining the class of previous studies to be used to predict the effects on T for a new intervention.
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Executive Plaza South, Room 8032, 1620 Executive Boulevard, MSC 7244, Bethesda, MD 20892-7244, USA. gailm@exchange.nih.gov
authors.forename: M H
authors.initials: MH
authors.lastname: Gail
authors.forename: R
authors.initials: R
authors.lastname: Pfeiffer
authors.forename: H C
authors.initials: HC
authors.lastname: Van Houwelingen
authors.forename: R J
authors.initials: RJ
authors.lastname: Carroll