ipcw {trtswitch}R Documentation

Inverse Probability of Censoring Weights (IPCW) Method for Treatment Switching

Description

Uses the inverse probability of censoring weights (IPCW) method to obtain the hazard ratio estimate of the Cox model to adjust for treatment switching.

Usage

ipcw(
  data,
  id = "id",
  stratum = "",
  tstart = "tstart",
  tstop = "tstop",
  event = "event",
  treat = "treat",
  swtrt = "swtrt",
  swtrt_time = "swtrt_time",
  base_cov = "",
  numerator = "",
  denominator = "",
  logistic_switching_model = FALSE,
  strata_main_effect_only = TRUE,
  firth = FALSE,
  flic = FALSE,
  ns_df = 3,
  stabilized_weights = TRUE,
  trunc = 0,
  trunc_upper_only = TRUE,
  swtrt_control_only = TRUE,
  alpha = 0.05,
  ties = "efron",
  boot = TRUE,
  n_boot = 1000,
  seed = NA
)

Arguments

data

The input data frame that contains the following variables:

  • id: The id to identify observations belonging to the same subject for counting process data with time-dependent covariates.

  • stratum: The stratum.

  • tstart: The starting time of the time interval for counting-process data with time-dependent covariates.

  • tstop: The stopping time of the time interval for counting-process data with time-dependent covariates.

  • event: The event indicator, 1=event, 0=no event.

  • treat: The randomized treatment indicator, 1=treatment, 0=control.

  • swtrt: The treatment switch indicator, 1=switch, 0=no switch.

  • swtrt_time: The time from randomization to treatment switch.

  • base_cov: The baseline covariates (excluding treat) used in the outcome model.

  • numerator: The baseline covariates (excluding treat) used in the numerator switching model for stabilized weights.

  • denominator: The baseline (excluding treat) and time-dependent covariates used in the denominator switching model.

id

The name of the id variable in the input data.

stratum

The name(s) of the stratum variable(s) in the input data.

tstart

The name of the tstart variable in the input data.

tstop

The name of the tstop variable in the input data.

event

The name of the event variable in the input data.

treat

The name of the treatment variable in the input data.

swtrt

The name of the swtrt variable in the input data.

swtrt_time

The name of the swtrt_time variable in the input data.

base_cov

The names of baseline covariates (excluding treat) in the input data for the Cox model.

numerator

The names of baseline covariates (excluding treat) in the input data for the numerator switching model for stabilized weights.

denominator

The names of baseline (excluding treat) and time-dependent covariates in the input data for the denominator switching model.

logistic_switching_model

Whether a pooled logistic regression switching model is used.

strata_main_effect_only

Whether to only include the strata main effects in the logistic regression switching model. Defaults to TRUE, otherwise all possible strata combinations will be considered in the switching model.

firth

Whether the Firth's bias reducing penalized likelihood should be used.

flic

Whether to apply intercept correction to obtain more accurate predicted probabilities.

ns_df

Degrees of freedom for the natural cubic spline for visit-specific intercepts of the pooled logistic regression model. Defaults to 3 for two internal knots at the 33 and 67 percentiles of the artificial censoring times due to treatment switching.

stabilized_weights

Whether to use the stabilized weights. The default is TRUE.

trunc

The truncation fraction of the weight distribution. Defaults to 0 for no truncation in weights.

trunc_upper_only

Whether to truncate the weights from the upper end of the weight distribution only. Defaults to TRUE, otherwise the weights will be truncated from both the lower and upper ends of the distribution.

swtrt_control_only

Whether treatment switching occurred only in the control group. The default is TRUE.

alpha

The significance level to calculate confidence intervals. The default value is 0.05.

ties

The method for handling ties in the Cox model, either "breslow" or "efron" (default).

boot

Whether to use bootstrap to obtain the confidence interval for hazard ratio. Defaults to TRUE.

n_boot

The number of bootstrap samples.

seed

The seed to reproduce the bootstrap results. The default is missing, in which case, the seed from the environment will be used.

Details

We use the following steps to obtain the hazard ratio estimate and confidence interval had there been no treatment switching:

Value

A list with the following components:

Author(s)

Kaifeng Lu, kaifenglu@gmail.com

References

James M. Robins and Dianne M. Finkelstein. Correcting for noncompliance and dependent censoring in an AIDS clinical trial with inverse probability of censoring weighted (IPCW) log-rank tests. Biometrics. 2000;56(3):779-788.

Examples


# Example 1: pooled logistic regression switching model

sim1 <- tsegestsim(
  n = 500, allocation1 = 2, allocation2 = 1, pbprog = 0.5, 
  trtlghr = -0.5, bprogsl = 0.3, shape1 = 1.8, 
  scale1 = 360, shape2 = 1.7, scale2 = 688, 
  pmix = 0.5, admin = 5000, pcatnotrtbprog = 0.5, 
  pcattrtbprog = 0.25, pcatnotrt = 0.2, pcattrt = 0.1, 
  catmult = 0.5, tdxo = 1, ppoor = 0.1, pgood = 0.04, 
  ppoormet = 0.4, pgoodmet = 0.2, xomult = 1.4188308, 
  milestone = 546, outputRawDataset = 1, seed = 2000)

fit1 <- ipcw(
  sim1$paneldata, id = "id", tstart = "tstart", 
  tstop = "tstop", event = "event", treat = "trtrand", 
  swtrt = "xo", swtrt_time = "xotime", base_cov = "bprog", 
  numerator = "bprog", denominator = "bprog*catlag", 
  logistic_switching_model = TRUE, ns_df = 3,
  swtrt_control_only = TRUE, boot = FALSE)
  
c(fit1$hr, fit1$hr_CI) 

# Example 2: time-dependent covariates Cox switching model

fit2 <- ipcw(
  shilong, id = "id", tstart = "tstart", tstop = "tstop", 
  event = "event", treat = "bras.f", swtrt = "co", 
  swtrt_time = "dco", 
  base_cov = c("agerand", "sex.f", "tt_Lnum", "rmh_alea.c", 
               "pathway.f"),
  numerator = c("agerand", "sex.f", "tt_Lnum", "rmh_alea.c", 
                "pathway.f"),
  denominator = c("agerand", "sex.f", "tt_Lnum", "rmh_alea.c",
                  "pathway.f", "ps", "ttc", "tran"),
  swtrt_control_only = FALSE, boot = FALSE)

c(fit2$hr, fit2$hr_CI)


[Package trtswitch version 0.1.8 Index]