getDurationFromNevents {lrstat}

Range of accrual duration for target number of events

Description

Obtains a range of accrual duration to reach the target number of events.

Usage

getDurationFromNevents(
  nevents = NA_real_,
  allocationRatioPlanned = 1,
  accrualTime = 0L,
  accrualIntensity = NA_real_,
  piecewiseSurvivalTime = 0L,
  stratumFraction = 1L,
  lambda1 = NA_real_,
  lambda2 = NA_real_,
  gamma1 = 0L,
  gamma2 = 0L,
  followupTime = NA_real_,
  fixedFollowup = 0L,
  npoints = 23L,
  interval = as.numeric(c(0.001, 240))
)

Arguments

nevents

The target number of events.

allocationRatioPlanned

Allocation ratio for the active treatment versus control. Defaults to 1 for equal randomization.

accrualTime

A vector that specifies the starting time of piecewise Poisson enrollment time intervals. Must start with 0, e.g., c(0, 3) breaks the time axis into 2 accrual intervals: [0, 3) and [3, Inf).

accrualIntensity

A vector of accrual intensities. One for each accrual time interval.

piecewiseSurvivalTime

A vector that specifies the starting time of piecewise exponential survival time intervals. Must start with 0, e.g., c(0, 6) breaks the time axis into 2 event intervals: [0, 6) and [6, Inf). Defaults to 0 for exponential distribution.

stratumFraction

A vector of stratum fractions that sum to 1. Defaults to 1 for no stratification.

lambda1

A vector of hazard rates for the event in each analysis time interval by stratum for the active treatment group.

lambda2

A vector of hazard rates for the event in each analysis time interval by stratum for the control group.

gamma1

The hazard rate for exponential dropout, a vector of hazard rates for piecewise exponential dropout applicable for all strata, or a vector of hazard rates for dropout in each analysis time interval by stratum for the active treatment group.

gamma2

The hazard rate for exponential dropout, a vector of hazard rates for piecewise exponential dropout applicable for all strata, or a vector of hazard rates for dropout in each analysis time interval by stratum for the control group.

followupTime

Follow-up time for the last enrolled subjects. Must be provided for fixed follow-up design.

fixedFollowup

Whether a fixed follow-up design is used. Defaults to 0 for variable follow-up.

npoints

The number of accrual duration time points. Defaults to 23.

interval

The interval to search for the solution of accrualDuration. Defaults to c(0.001, 240).

Value

A data frame of the following variables:

• nevents: The target number of events.

• fixedFollowup: Whether a fixed follow-up design is used.

• accrualDuration: The accrual duration.

• subjects: The total number of subjects.

• followupTime: The follow-up time for the last enrolled subject.

• studyDuration: The study duration.

Author(s)

Kaifeng Lu, [e-mail]

Examples

# Piecewise accrual, piecewise exponential survivals, and 5% dropout by
# the end of 1 year.

getDurationFromNevents(
  nevents = 80, allocationRatioPlanned = 1,
  accrualTime = seq(0, 8),
  accrualIntensity = 26/9*seq(1, 9),
  piecewiseSurvivalTime = c(0, 6),
  stratumFraction = c(0.2, 0.8),
  lambda1 = c(0.0533, 0.0309, 1.5*0.0533, 1.5*0.0309),
  lambda2 = c(0.0533, 0.0533, 1.5*0.0533, 1.5*0.0533),
  gamma1 = -log(1-0.05)/12,
  gamma2 = -log(1-0.05)/12,
  fixedFollowup = FALSE)