calcDuration {debest}

Calculate the study duration based on Weibull distributions.

Description

Calculate the study duration based on Weibull distributions.

Usage

calcDuration(
  d,
  n,
  proportion,
  SHAPEV,
  SCALEV,
  LAMW,
  A,
  BETA,
  conf.level = 0.9,
  nsim = 10000
)

Arguments

d

- scalar, target number of events.

n

- scalar, sample size.

proportion

- vector of percentages of the subgroup.

SHAPEV

- vector of shape parameters of Weibull survival distributions of the subgroups.

SCALEV

- vector of scale parameters of Weibull survival distributions of the subgroups.

LAMW

- vector of exponential drop-out distribution parameters of the subgroups.

A

- vector of enrollment durations of the subgroups.

BETA

- vector of beta distribution parameters of the subgroups.

conf.level

- scalar, confidence level, default 0.9.

nsim

- scalar, number of repetitions, default 1e4.

Value

study duration estimate, d_med, and the confidence interval (d_lower, d_upper), as well as all the realizations, Z_d, of the study duration from the simulation.

References

Hong Zhang, Jie Pu, Shibing Deng, Satrajit Roychoudhury, Haitao Chu and Douglas Robinson. "Study Duration Prediction for Clinical Trials with Time-to-Event Endpoints Using Mixture Distributions Accounting for Heterogeneous Population", arXiv:2401.00540.

Examples

res_weibull = getWeilbull(dat_udca)
res_beta = getBeta(as.numeric(dat_udca$entry.dt))
prop = c(table(dat_udca$group)/length(dat_udca$group))
SHAPEV = res_weibull$shape
SCALEV = res_weibull$scale
LAMW = rep(-log(1 - 0.1)/6, 4)
A = rep(res_beta$a/30.416, 4) # convert days to months
BETA = rep(res_beta$b_Mean, 4)
myres1 = calcDuration(d=50, n=169, proportion=prop, SHAPEV, SCALEV, LAMW=LAMW, A, BETA)
c(myres1$d_lower, myres1$d_med, myres1$d_upper)
# drop-out will make the target number of events not achievable
myres2 = calcDuration(d=80, n=169, proportion=prop, SHAPEV, SCALEV, LAMW=LAMW, A, BETA)
c(myres2$d_lower, myres2$d_med, myres2$d_upper)
# If there is no drop-out
myres3 = calcDuration(d=80, n=169, proportion=prop, SHAPEV, SCALEV, LAMW=rep(0, 4), A, BETA)
c(myres3$d_lower, myres3$d_med, myres3$d_upper)