rpact (version 1.0.0)

getSampleSizeSurvival: Get Sample Size Survival

Description

Returns the sample size for testing the hazard ratio in a two treatment groups survival design.

Usage

getSampleSizeSurvival(design, ..., typeOfComputation = "Schoenfeld",
  thetaH0 = 1, pi2 = 0.2, pi1 = seq(0.4, 0.6, 0.1),
  allocationRatioPlanned = 1, accountForObservationTimes = NA,
  eventTime = NA_real_, accrualTime = NA_real_, followUpTime = NA_real_,
  maxNumberOfPatients = 0, dropOutRate1 = 0, dropOutRate2 = 0,
  dropOutTime = NA_real_)

Arguments

design

The trial design.

...

Ensures that all arguments are be named and that a warning will be displayed if unknown arguments are passed.

typeOfComputation

Three options are available: "Schoenfeld", "Freedman", "HsiehFreedman", the default is "Schoenfeld". For details, see Hsieh (Statistics in Medicine, 1992).

thetaH0

The null hypothesis value. The default value is 1. For one-sided testing, a bound for testing H0: log(1 - pi1)/log(1 - pi2) = thetaH0 != 1 can be specified.

pi2

The assumed event rate in the control group, default is 0.2.

pi1

The assumed event rate in the treatment group, default is seq(0.4, 0.6, 0.1).

allocationRatioPlanned

The planned allocation ratio, default is 1. If allocationRatioPlanned = 0 is entered, the optimal allocation ratio yielding the smallest number of patients is determined.

accountForObservationTimes

If accountForObservationTimes = TRUE, the number of patients is calculates assuming assuming specific accrual and follow-up time. The formula of Kim & Tsiatis (Biometrics, 1990) is used to calculated the expected number of events under the alternative (see also Lakatos & Lan, Statistics in Medicine, 1992).

eventTime

The assumed time under which the event rates are calculated (need to be specified if accountForObservationTimes = TRUE).

accrualTime

The assumed accrual time for the study (need to be specified if accountForObservationTimes = TRUE).

followUpTime

The assumed (additional) follow-up time for the study (need to be specified if accountForObservationTimes = TRUE). The total study duration is accrualTime + followUpTime.

maxNumberOfPatients

For accountForObservationTimes = TRUE, if maxNumberOfPatients > 0 is specified, the follow-up time for the required number of events is determined.

dropOutRate1

The assumed drop-out rate in the control group, default is 0.

dropOutRate2

The assumed drop-out rate in the treatment group, default is 0.

dropOutTime

The assumed time for drop-out rates in the control and the treatment group, default is 12.

Value

Returns a TrialDesignPlanSurvival object.

Details

At given design the function calculates the number of events and an estimate for the necessary number of patients for testing the hazard ratio log(1 - p1)/log(1 - p2) with no interim stages. Accordingly, an event probability omega is calculated. It also calculates the time when the required events are expected under the given assumptions (assuming exponentially distributed survival times). Furthermore, an allocation ratio = n1Fixed/n2Fixed can be specified.

Examples

# NOT RUN {
# Calculate the number of events and number of patients calculated with 
# the Schoenfeld formula.
getSampleSizeSurvival(getDesignGroupSequential(alpha = 0.025, beta = 0.2, 
    sided = 1), thetaH0 = 1, pi1 = 0.6, pi2 = 0.9, 
    allocationRatioPlanned = 2, typeOfComputation = "Schoenfeld")

# Calculate analysis times, number of aevent, and number of patients 
# under specified event, accrual, followup, and dropout time and event 
# and dropout rates.
getSampleSizeSurvival(getDesignGroupSequential(alpha = .025, sided = 1), 
    pi1 = c(0.25, 0.3, 0.35), pi2 = 0.4, allocationRatioPlanned = 0, 
    typeOfComputation = "Schoenfeld", accountForObservationTimes = TRUE,
    eventTime = 12, accrualTime = 6, followUpTime = 12, 
    maxNumberOfPatients = 0, dropOutRate1 = 0.15, dropOutRate2 = 0.1, 
    dropOutTime = 24)

# }