Comparing restricted mean survival time

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Description

Performs two-sample comparisons using the restricted mean survival time (RMST) as a summary measure of the survival time distribution. Three kinds of between-group contrast metrics (i.e., the difference in RMST, the ratio of RMST and the ratio of the restricted mean time lost (RMTL)) are computed. It performs ANCOVA-type adjusted analyses when covariates are passed to it as an argument.

Usage

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rmst2(time, status, arm, tau = NULL, covariates = NULL, alpha = 0.05)

Arguments

time

The follow-up time for right censored data.

status

The status indicator, 1=event, and 0=right censored.

arm

The group indicator for comparison. The elements of this vector take either 1 or 0. Normally, 0=control group, 1=active treatment group.

tau

A scaler value to specify the truncation time point for the RMST calculation. tau needs to be smaller than the minimum of the largest observed time in each of the two groups. When tau = NULL, the default value (i.e., the minimum of the largest observed "event" time in each of the two groups) is used.

covariates

This specifies covariates to be used for the adjusted analyses. When NULL, unadjusted analyses are performed. When non NULL, the ANOCVA-type adjusted analyses are performed using those variables passed as covariates. This can be one variable (vector) or more than one variables (matrix).

alpha

The default is 0.05. (1-alpha) confidence intervals are reported.

Details

For more details, please see the package vignette.

Value

an object of class rmst2.

tau

the truncation time used in the analyses

note

a note regarding the truncation time

RMST.arm1

RMST results in arm 1. This is generated only when covariates is not specified.

RMST.arm0

RMST results in arm 0. This is generated only when covariates is not specified.

unadjusted.result

Results of the unadjusted analyses. This is generated only when covariates is not specified.

The values below are generated when some covariates are passed to the function.

adjusted.result

Results of the adjusted analyses.

RMST.difference.adjusted

Results of the parameter estimates with the model to derive an adjusted difference in RMST.

RMST.ratio.adjusted

Results of the parameter estimates with the model to derive an adjusted ratio of RMST.

RMTL.ratio.adjusted

Results of the parameter estimates with the model to derive an adjusted ratio of RMTL.

Author(s)

Hajime Uno, Lu Tian, Angel Cronin, Chakib Battioui

References

Uno H, Claggett B, Tian L, Inoue E, Gallo P, Miyata T, Schrag D, Takeuchi M, Uyama Y, Zhao L, Skali H, Solomon S, Jacobus S, Hughes M, Packer M, Wei LJ. Moving beyond the hazard ratio in quantifying the between-group difference in survival analysis. Journal of clinical Oncology 2014, 32, 2380-2385.

Tian L, Zhao L, Wei LJ. Predicting the restricted mean event time with the subject's baseline covariates in survival analysis. Biostatistics 2014, 15, 222-233.

Examples

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#--- sample data ---#
D=rmst2.sample.data()
time=D$time
status=D$status
arm=D$arm
tau=NULL
x=D[,c(4,6,7)]

#--- without covariates ----
a=rmst2(time, status, arm, tau=10)
print(a)
plot(a, xlab="Years", ylab="Probability", density=60)

#--- with covariates ----
a=rmst2(time, status, arm, tau=10, covariates=x)
print(a)