R: compare the performance of two treatment selection markers

compare.trtsel {TreatmentSelection}

R Documentation

compare the performance of two treatment selection markers

Description

Evaluates and compares the performance of two treatment selection markers measured in the same data. (Bias-corrected) summary measures for the performance of each marker are estimated and confidence intervals are provided. Differences in measures of performance between markers are estimated along with confidence intervals, and the results of tests comparing marker performance measures are returned. "Treatment effect curves" for each marker are overlaid on the same plot. An object of class 'trtsel' must first be created for each marker using the function 'trtsel' by supplying a data.frame containing marker, treatment, and event status information; treatment and event data must be identical for the two markers.

Usage

## S3 method for class 'trtsel'
compare(x, ..., x2, bootstraps = 500, bias.correct = TRUE,
  alpha = 0.05, plot = TRUE, ci = "horizontal", fixed.values = NULL,
  offset = 0.01, conf.bands = TRUE, conf.bandsN = 100,
  model.names = c("Model 1", "Model 2"), xlab = NULL, ylab = NULL,
  xlim = NULL, ylim = NULL, main = NULL, annotate.plot = TRUE)

Arguments

`x`	An object of class "trtsel" created by using function "trtsel". This is created using data for the first marker. Note: event and treatment vectors provided to create this trtsel object must be identical to those used to create the x2 object.
`...`	ignored.
`x2`	An object of class "trtsel" created by using function "trtsel". This is created using data for the second marker.
`bootstraps`	Number of bootstrap replicates for creating confidence intervals and bands. Default value is 500. Set bootstraps=0 if no confidence intervals or bands are desired.
`bias.correct`	logical indicator of whether to bias-correct measures for over-optimism using bootstrap-bias correction. When the same data is used to fit and evaluate the model, performance measures are over-optimistic. Setting this equal to TRUE uses a bootstrap method to bias-correct performance measures.
`alpha`	(1-alpha)*100% confidence intervals are calculated. Default value is alpha = 0.05 which yields 95% CI's.
`plot`	Indication of whether a plot showing treatment effect curves for the two markers should be created. TRUE (default) or FALSE.
`ci`	If plot = TRUE, indication of whether horizontal or vertical confidence intervals be plotted. Character string of either "horizontal" (default) or "vertical." Only applies if plot = TRUE.
`fixed.values`	A numeric vector indicating fixed values on the x- or y-axes at which bootstrap confidence intervals are provided. If "fixed.values" are provided, point-wise confidence intervals will be printed (i.e. conf.bands will be taken as FALSE). This option applies to the plot only.
`offset`	If confidence intervals are to be plotted for specified fixed.values, offset is the amount of distance to offset confidence intervals so that they do not overlap on the plot. The default value is 0.01. Only applies if plot = TRUE.
`conf.bands`	Indication of whether pointwise confidence intervals are shown for the curve(s). TRUE (default) or FALSE. If "fixed.values" are input, this option is ignored and no confidence bands are produced. Only applies if plot = TRUE.
`conf.bandsN`	If conf.bands = TRUE, the number of points along the x- or y-axis at which to calculate the pointwise confidence intervals. The default is 100. Only applies if plot = TRUE.
`model.names`	A vector of length 2 indicating the names for the two markers in x, and x2, respectively, for the plot legend. The default value is c("Model 1", "Model 2").
`xlab`	A label for the x-axis. Default values depend on plot.type. Only applies if plot = TRUE.
`ylab`	A label for the y-axis. Default values depend on plot.type. Only applies if plot = TRUE.
`xlim`	The limits for the x-axisof the plot, in the form c(x1,x2). Only applies if plot = TRUE.
`ylim`	The limits for the y-axis of the plot, in the form c(y1,y2). Only applies if plot = TRUE.
`main`	The main title for the plot. Only applies if plot = TRUE.
`annotate.plot`	Only applies to comparison of two discrete markers. Should the plot be annotated with the marker group percentages? default is TRUE.

Value

A list with components (see Janes et al. (2013) for a description of the summary measures and estimators):

`estimates.marker1`	Point estimates of the summary measures: p.neg, p.pos, B.neg, B.pos, Theta, Var.Delta, TG and event rates for marker 1.
`estimates.marker2`	Point estimates for the same summary measures for marker 2.
`estimates.diff`	Estimated difference in summary measures (marker 1 - marker 2).
`ci.marker1`	2x9 data.frame with confidence intervals for marker 1 performance measures.
`ci.marker2`	2x9 data.frame with confidence intervals for marker 2 performance measures.
`ci.diff`	2x9 data.frame with confidence intervals for differences in performance measures.
`p.values`	1x9 data.frame with p-values for each difference corresponding to a test of H0: marker 1 performance = marker 2 performance.
`bootstraps`	bootstraps value provided.

In addition, if plot = TRUE:

`plot`	ggplot object containing the generated plot.
`plot.ci.marker1`	A data.frame containing the bounds of the bootstrap-based confidence intervals for marker1, along with the fixed.values they are centered around, where applicable.
`plot.ci.marker2`	a data.frame containing the bounds of the bootstrap-based confidence intervals for marker 2, along with the fixed.values they are centered around, where applicable.

Note

Plot output is only produced when comparing a continuous (discrete) marker to a continuous (discrete) marker because confidence bands are calculated differently for continuous vs. discrete markers. See the note under ?plot.trtsel, for a description of the differences between how the bootstrap confidence bands are calculated.

References

Janes, Holly; Brown, Marshall D; Pepe, Margaret; Huang, Ying; "An Approach to Evaluating and Comparing Biomarkers for Patient Treatment Selection" The International Journal of Biostatistics. Volume 0, Issue 0, ISSN (Online) 1557-4679, ISSN (Print) 2194-573X, DOI: 10.1515/ijb-2012-0052, April 2014

Examples



data(tsdata)

###########################
## Create trtsel objects 
###########################

trtsel.Y1 <- trtsel(event ~ Y1*trt, 
                   treatment.name = "trt", 
                   data = tsdata, 
                   study.design = "RCT",
                   default.trt = "trt all")

trtsel.Y1

trtsel.Y2 <- trtsel(event ~ Y2*trt, 
                   treatment.name = "trt", 
                   data = tsdata, 
                   default.trt = "trt all")
trtsel.Y2
                          

###############################
## Compare marker performance
###############################


# Plot treatment effect curves with pointwise confidence intervals
## use more bootstraps in practice
compare(x = trtsel.Y1, x2 = trtsel.Y2,
                                bootstraps = 10, plot = TRUE,      
                                ci = "horizontal",  conf.bands = TRUE)

[Package TreatmentSelection version 2.1.1 Index]