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\name{dat.fine1993}
\docType{data}
\alias{dat.fine1993}
\title{Studies on Radiation Therapy with or without Adjuvant Chemotherapy in Patients with Malignant Gliomas}
\description{Results from 17 trials comparing post-operative radiation therapy with and without adjuvant chemotherapy in patients with malignant gliomas.}
\usage{
dat.fine1993
}
\format{The data frame contains the following columns:
\tabular{lll}{
\bold{study} \tab \code{numeric} \tab study number \cr
\bold{nei} \tab \code{numeric} \tab sample size in the experimental group receiving radiotherapy plus adjuvant chemotherapy \cr
\bold{nci} \tab \code{numeric} \tab sample size in the control group receiving radiotherapy alone \cr
\bold{e1i} \tab \code{numeric} \tab number of survivors at 6 months in the experimental group \cr
\bold{c1i} \tab \code{numeric} \tab number of survivors at 6 months in the control group \cr
\bold{e2i} \tab \code{numeric} \tab number of survivors at 12 months in the experimental group \cr
\bold{c2i} \tab \code{numeric} \tab number of survivors at 12 months in the control group \cr
\bold{e3i} \tab \code{numeric} \tab number of survivors at 18 months in the experimental group \cr
\bold{c3i} \tab \code{numeric} \tab number of survivors at 18 months in the control group \cr
\bold{e4i} \tab \code{numeric} \tab number of survivors at 24 months in the experimental group \cr
\bold{c4i} \tab \code{numeric} \tab number of survivors at 24 months in the control group
}
}
\details{
The 17 trials report the post-operative survival of patients with malignant gliomas receiving either radiation therapy with adjuvant chemotherapy or radiation therapy alone. Survival was assessed at 6, 12, 18, and 24 months in all but one study (which assessed survival only at 12 and at 24 months).
The data were reconstructed by Trikalinos and Olkin (2012) based on Table 2 in Fine et al. (1993) and Table 3 in Dear (1994). The data can be used to illustrate how a meta-analysis can be conducted of effect sizes reported at multiple time points using a multivariate model.
}
\source{
Dear, K. B. G. (1994). Iterative generalized least squares for meta-analysis of survival data at multiple times. \emph{Biometrics}, \bold{50}(4), 989--1002. \verb{https://doi.org/10.2307/2533438}
Trikalinos, T. A., & Olkin, I. (2012). Meta-analysis of effect sizes reported at multiple time points: A multivariate approach. \emph{Clinical Trials}, \bold{9}(5), 610--620. \verb{https://doi.org/10.1177/1740774512453218}
}
\references{
Fine, H. A., Dear, K. B., Loeffler, J. S., Black, P. M., & Canellos, G. P. (1993). Meta-analysis of radiation therapy with and without adjuvant chemotherapy for malignant gliomas in adults. \emph{Cancer}, \bold{71}(8), 2585--2597. \verb{https://doi.org/10.1002/1097-0142(19930415)71:8<2585::aid-cncr2820710825>3.0.co;2-s}
}
\author{
Wolfgang Viechtbauer, \email{wvb@metafor-project.org}, \url{https://www.metafor-project.org}
}
\examples{
### copy data into 'dat' and examine data
dat <- dat.fine1993
dat
\dontrun{
### load metafor package
library(metafor)
### calculate log(ORs) and sampling variances for each time point
dat <- escalc(measure="OR", ai=e1i, n1i=nei, ci=c1i, n2i=nci, data=dat, var.names=c("y1i","v1i"))
dat <- escalc(measure="OR", ai=e2i, n1i=nei, ci=c2i, n2i=nci, data=dat, var.names=c("y2i","v2i"))
dat <- escalc(measure="OR", ai=e3i, n1i=nei, ci=c3i, n2i=nci, data=dat, var.names=c("y3i","v3i"))
dat <- escalc(measure="OR", ai=e4i, n1i=nei, ci=c4i, n2i=nci, data=dat, var.names=c("y4i","v4i"))
### calculate the covariances (equations in Appendix of Trikalinos & Olkin, 2012)
dat$v12i <- with(dat, nei / (e1i * (nei - e2i)) + nci / (c1i * (nci - c2i)))
dat$v13i <- with(dat, nei / (e1i * (nei - e3i)) + nci / (c1i * (nci - c3i)))
dat$v14i <- with(dat, nei / (e1i * (nei - e4i)) + nci / (c1i * (nci - c4i)))
dat$v23i <- with(dat, nei / (e2i * (nei - e3i)) + nci / (c2i * (nci - c3i)))
dat$v24i <- with(dat, nei / (e2i * (nei - e4i)) + nci / (c2i * (nci - c4i)))
dat$v34i <- with(dat, nei / (e3i * (nei - e4i)) + nci / (c3i * (nci - c4i)))
### create dataset in long format
dat.long <- data.frame(study=rep(1:nrow(dat), each=4), time=1:4,
yi=c(t(dat[c("y1i","y2i","y3i","y4i")])),
vi=c(t(dat[c("v1i","v2i","v3i","v4i")])))
### var-cov matrices of the sudies
V <- lapply(split(dat, dat$study),
function(x) matrix(c( x$v1i, x$v12i, x$v13i, x$v14i,
x$v12i, x$v2i, x$v23i, x$v24i,
x$v13i, x$v23i, x$v3i, x$v34i,
x$v14i, x$v24i, x$v34i, x$v4i), nrow=4, ncol=4, byrow=TRUE))
### remove rows for the missing time points in study 17
dat.long <- na.omit(dat.long)
### remove corresponding rows/columns from var-cov matrix
V[[17]] <- V[[17]][c(2,4),c(2,4)]
### make a copy of V
Vc <- V
### replace any (near) singular var-cov matrices with ridge corrected versions
repl.Vi <- function(Vi) {
res <- eigen(Vi)
if (any(res$values <= .08)) {
round(res$vectors \%*\% diag(res$values + .08) \%*\% t(res$vectors), 12)
} else {
Vi
}
}
Vc <- lapply(Vc, repl.Vi)
### do not correct var-cov matrix of study 17
Vc[[17]] <- V[[17]]
### construct block diagonal matrix
Vc <- bldiag(Vc)
### multivariate fixed-effects model
res <- rma.mv(yi, Vc, mods = ~ factor(time) - 1, method="FE", data=dat.long)
print(res, digits=3)
### multivariate random-effects model with heteroscedastic AR(1) structure for the true effects
res <- rma.mv(yi, Vc, mods = ~ factor(time) - 1, random = ~ time | study,
struct="HAR", data=dat.long, control=list(optimizer="hjk"))
print(res, digits=3)
### profile the variance components
par(mfrow=c(2,2))
profile(res, tau2=1, xlim=c( 0,.2))
profile(res, tau2=2, xlim=c( 0,.2))
profile(res, tau2=3, xlim=c( 0,.2))
profile(res, tau2=4, xlim=c(.1,.3))
### profile the autocorrelation coefficient
par(mfrow=c(1,1))
profile(res, rho=1)
}
}
\keyword{datasets}
\concept{medicine}
\concept{oncology}
\concept{odds ratios}
\concept{longitudinal models}
\section{Concepts}{
medicine, oncology, odds ratios, longitudinal models
}
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