Updating the Accrual Rate of a Trial at a Milestone

update the accrual rate of the recruitment curve at a milestone. The enroller of a trial is always StaggeredRecruiter; this function replaces its accrual_rate for patients not yet enrolled, while enrolled patients are left unchanged. This function can be used in adaptive designs; its application includes, but is not limited to, revising recruitment after dose selection or enrichment, or pausing recruitment for a period after an interim decision.

end_time in accrual_rate is measured from the time this function is called (i.e., the current milestone), not from the start of the trial. A milestone is usually event driven, so its calendar time is unknown until the trial is simulated, and a schedule on the calendar time scale could not be pre-specified. Measuring end_time from the milestone also lets users state the new plan simply as "from now on": e.g., data.frame(end_time = c(3, Inf), piecewise_rate = c(20, 35)) means 20 patients per month for the 3 months following the milestone and 35 per month thereafter, whenever the milestone occurs. Following the convention of StaggeredRecruiter, the first re-planned patient is enrolled 1/piecewise_rate after the milestone; a leading window with piecewise_rate = 0 defers enrollment further. As with other adaptations, patients not yet enrolled are re-randomized and their data are regenerated under the new schedule.

Note that this function should only be called within action functions of milestones. It is users' responsibility to ensure that and TrialSimulator has no way to track it. Calling it before any milestone has been triggered is an error.

This is a user-friendly wrapper of the member function of trial, i.e., Trials$update_accrual_rate(), which is used in vignettes. Users who are not familiar with the concept of classes may consider using this wrapper directly.

Usage

update_accrual_rate(trial, accrual_rate)

Arguments

trial

a trial object returned by trial().

accrual_rate

a data frame of columns end_time and piecewise_rate as in StaggeredRecruiter, with end_time measured from the current milestone. The last end_time must be Inf with a positive rate.