examine {crmPack}

Obtain hypothetical trial course table for a design

Description

This generic function takes a design and generates a dataframe showing the beginning of several hypothetical trial courses under the design. This means, from the generated dataframe one can read off: - how many cohorts are required in the optimal case (no DLTs observed) in order to reach the highest dose of the specified dose grid (or until the stopping rule is fulfilled) - assuming no DLTs are observed until a certain dose level, what the next recommended dose is for all possible number of DLTs observed - the actual relative increments that will be used in these cases - whether the trial would stop at a certain cohort Examining the "single trial" behavior of a dose escalation design is the first important step in evaluating a design, and cannot be replaced by studying solely the operating characteristics in "many trials". The cohort sizes are also taken from the design, assuming no DLTs occur until the dose listed.

Usage

examine(object, ..., maxNoIncrement = 100L)

## S4 method for signature 'Design'
examine(object, mcmcOptions = McmcOptions(), ..., maxNoIncrement)

## S4 method for signature 'RuleDesign'
examine(object, ..., maxNoIncrement = 100L)

Arguments

object

the design (Design or RuleDesign object) we want to examine

...

additional arguments (see methods)

maxNoIncrement

maximum number of contiguous next doses at 0 DLTs that are the same as before, i.e. no increment (default to 100)

mcmcOptions

object of class McmcOptions, giving the MCMC options for each evaluation in the trial. By default, the standard options are used

Value

The data frame

Functions

• examine(Design): Examine a model-based CRM

• examine(RuleDesign): Examine a rule-based design

Examples

# Define the dose-grid
emptydata <- Data(doseGrid = c(1, 3, 5, 10, 15, 20, 25))

# Initialize the CRM model 
model <- LogisticLogNormal(mean=c(-0.85, 1),
                           cov=
                             matrix(c(1, -0.5, -0.5, 1),
                                    nrow=2),
                           refDose=56)

# Choose the rule for selecting the next dose 
myNextBest <- NextBestNCRM(target=c(0.2, 0.35),
                           overdose=c(0.35, 1),
                           maxOverdoseProb=0.25)

# Choose the rule for the cohort-size 
mySize1 <- CohortSizeRange(intervals=c(0, 30),
                           cohortSize=c(1, 3))
mySize2 <- CohortSizeDLT(DLTintervals=c(0, 1),
                         cohortSize=c(1, 3))
mySize <- maxSize(mySize1, mySize2)

# Choose the rule for stopping
myStopping1 <- StoppingMinCohorts(nCohorts=3)
myStopping2 <- StoppingTargetProb(target=c(0.2, 0.35),
                                  prob=0.5)
myStopping3 <- StoppingMinPatients(nPatients=20)
myStopping <- (myStopping1 & myStopping2) | myStopping3

# Choose the rule for dose increments
myIncrements <- IncrementsRelative(intervals=c(0, 20),
                                   increments=c(1, 0.33))

# Initialize the design
design <- Design(model=model,
                 nextBest=myNextBest,
                 stopping=myStopping,
                 increments=myIncrements,
                 cohortSize=mySize,
                 data=emptydata,
                 startingDose=3)

# Examine the design
set.seed(4235)
# MCMC parameters are set to small values only to show this example. They should be
# increased for a real case.
options <- McmcOptions(burnin=10,step=1,samples=20)
examine(design, options)
  
## example where examine stops because stopping rule already fulfilled
myStopping4 <- StoppingMinPatients(nPatients=3)
myStopping <- (myStopping1 & myStopping2) | myStopping4
design <- Design(model=model,
                 nextBest=myNextBest,
                 stopping=myStopping,
                 increments=myIncrements,
                 cohortSize=mySize,
                 data=emptydata,
                 startingDose=3)
examine(design,mcmcOptions=options)

## example where examine stops because infinite looping
## (note that here a very low threshold is used for the parameter
## "maxNoIncrement" in "examine" to keep the execution time short)
myIncrements <- IncrementsRelative(intervals=c(0, 20),
                                   increments=c(1, 0.00001))
myStopping <- (myStopping1 & myStopping2) 
design <- Design(model=model,
                 nextBest=myNextBest,
                 stopping=myStopping,
                 increments=myIncrements,
                 cohortSize=mySize,
                 data=emptydata,
                 startingDose=3)
examine(design, mcmcOptions=options, maxNoIncrement = 2)

# Define the dose-grid
emptydata <- Data(doseGrid = c(5, 10, 15, 25, 35, 50, 80))

# inizialing a 3+3 design with constant cohort size of 3 and
# starting dose equal 5
myDesign <- RuleDesign(nextBest = NextBestThreePlusThree(),
                       cohortSize = CohortSizeConst(size=3L),
                       data = emptydata,
                       startingDose = 5)
  
# Examine the design
set.seed(4235)
examine(myDesign)