Title

artpep -- ART (Survival Outcomes) - Projection of Events and Power

Syntax

artpep
[using filename[.dta]]
[
,
options
]

datestart(ddmmmyyyy) Calendar date of trial opening

edf0(slist0) Survival function in group

eperiods(#) Number of future periods
over which projection of power and number of events is to be calculated

epts(numlist) Numbers of additional patients to be recruited in each period

pts(numlist) Numbers of patients recruited in each period since the start of the trial

replace Allows filename to be replaced if it exists

startperiod(#) Period to start reporting projections of events and power

stoprecruit(#) Number of periods after which recruitment is to cease

artsurv_options Options appropriate to artsurv

Description

artpep estimates the number of events and power achieved in real
time as patients are recruited to a clinical trial with a time-to-event
outcome. It allows projection of events and power into the future,
allowing "what if?" sensitivity analyses to be evaluated. For example,
the effect on power of future patterns of patient accrual and survival
might be studied. Quantities calculated by artpep may optionally
be stored in a new Stata file called filename to facilitate further
analysis, plotting, etc.

Note that artpep is available either as a command-line program
(described here) or via a dialog, invoked by typing db artpep.
A separate help file (artpepdlg) is available for the dialog.
Running the dialog will also generate the equivalent command line for
artpep.

See Remarks for details of using filename.

Options

datestart(ddmmmyyyy) signifies the date of opening of the trial (i.e.
when recruitment started). The date of the end of each period is used
to label the output, and is stored in filename if using is
specified. Example: datestart(14oct2009).

edf0(slist0) is not optional and gives the survival
function in the control group (group 1).
This need not be one of the survival distributions to be compared
in the trial, unless hratio = 1 for at least one of the groups. The format of
slist0 is #1[#2 ...#r,#1 #2 ...#r].
Thus, edf0(p_1 p_2 ... p_r,t_1 t_2 ... t_r) gives the
value p_i for the survival function for the event time at the
end of time period t_i, i=1,...,r. Instantaneous event rates (i.e. hazards)
are assumed constant within time periods, that is,
the distribution of time-to-event is assumed to be piecewise exponential.
Note that when used in a given calculation up to period T, t_r may validly be
less than, equal to or greater than T. If t_r <= T, the rules described in the
edf0() option of artsurv are applied to compute the survival
function at all periods <=T. If t_r > T, the same calculation is used but
estimated survival probabilities for periods > T are not used
in the calculation at T, although they may of course be used in calculations
(e.g. projections of sample size and events) for periods later than T.

Be aware that use of the median() and fp()
options of artsurv may modify the effects
and interpretation of edf0().

eperiods(#) specifies the number of 'extra' (future) periods
over which projection of power and number of events is to be calculated.
Default # is 1.

epts(numlist) specifies in numlist the
numbers of 'extra' (additional) patients to be recruited in each period following
the recruitment phase defined by the pts() option. For example,
pts(23 12 25) epts(30 30) would specify 3 initial periods of
recruitment followed by 2 further periods. A projection of events and power
is required over the 2 further periods. The initial recruitment
is of 23 patients in period 1, 12 in period 2 and 25 in period 3;
in each of periods 4 and 5, we expect to recruit an additional 30 patients.
If the number of items in (or implied by expanding) numlist is less
than that specifed by pts(), the final value in numlist
is replicated as necessary to all subsequent periods. If epts()
is not given, the default is that the mean of the numbers of patients
specified in pts() is used for all projections.

pts(numlist) is not optional. numlist specifies the
numbers of patients recruited in each period since the start of the trial,
i.e. since randomisation. See artsurv for the definition of a 'period'.
The number of items in numlist defines the number of periods of recruitment so far.
For example, pts(23 12 25) specifies 3 initial periods of
recruitment, with recruitment of 23 patients in period 1, 12 in period 2,
and 25 in period 3. The 'current' period would be period 3 and would be
surrounded by parallel lines in the output.

replace allows filename to be replaced if it exists.

startperiod(#) specifies # as the period to start
reporting the projections of events and power. To report from the
beginning of the trial, specify startperiod(1). Note that
startperiod() does not affect the period at which the
calculations are started, only how the results are reported.
The default # is the last period defined by pts().

stoprecruit(#) specifies the number of periods after which recruitment is
to cease. # must be no smaller than the number of periods of
recruitment implied by pts(). Default # = 0,
meaning continue recruiting indefinitely (no follow-up phase).

artsurv_options are any of the options of artsurv except recrt(),
nperiod(), power(), n().

Remarks

The using filename[{cmd:.dta] construct saves items to
filename.dta, as in the following example:

. artpep using myres, pts(15 14 15 16 19 40 44 63 65 56 65 59 78 67) epts(65)
eperiods(7) startperiod(1) stoprecruit(15) datestart(24apr2001) alpha(.05)
aratios(1 1) hratio(1, .75) ngroups(2) ni(0) onesided(0) trend(0) tunit(3)
edf0(0.49 0.26 0.19 0.085 0.057, 4(4)20) median(0) method(l)

Date | quarter | #pats #C-events #events Power
----------+----------+-----------------------------------------
23jul2001 | 1 | 15 1 2 0.03521
22oct2001 | 2 | 29 3 5 0.04761
21jan2002 | 3 | 44 5 9 0.06248
23apr2002 | 4 | 60 9 16 0.08023
23jul2002 | 5 | 79 13 23 0.10128
22oct2002 | 6 | 119 19 34 0.12981
22jan2003 | 7 | 163 28 49 0.16942
23apr2003 | 8 | 226 39 70 0.22272
23jul2003 | 9 | 291 54 97 0.29037
23oct2003 | 10 | 347 70 128 0.36653
22jan2004 | 11 | 412 89 162 0.44703
22apr2004 | 12 | 471 110 200 0.52800
23jul2004 | 13 | 549 133 242 0.60767
----------+----------+-----------------------------------------
22oct2004 | 14 | 616 157 288 0.68285
----------+----------+-----------------------------------------
21jan2005 | 15 | 681 183 336 0.74893
23apr2005 | 16 | 681 206 381 0.79989
23jul2005 | 17 | 681 226 418 0.83529
22oct2005 | 18 | 681 241 449 0.86056
21jan2006 | 19 | 681 254 475 0.87914
23apr2006 | 20 | 681 265 497 0.89332
23jul2006 | 21 | 681 275 517 0.90446

file myres.dta saved

. use myres, replace

. describe

Contains data from myres.dta
obs: 21
vars: 6 19 Sep 2012 09:31
size: 504
---------------------------------------------------------------------------
storage display value
variable name type format label variable label
---------------------------------------------------------------------------
date float %td date of end of period
period float %9.0g quarter period
patients float %9.0g Cumulative patients
Events float %9.0g Cumulative control-arm events
events float %9.0g Cumulative total events
power float %9.0g Power
---------------------------------------------------------------------------

. list

+------------------------------------------------------------+
| date period patients Events events power |
|------------------------------------------------------------|
1. | 23jul2001 1 15 1 2 .0352053 |
2. | 22oct2001 2 29 3 5 .0476124 |
3. | 21jan2002 3 44 5 9 .0624845 |
4. | 23apr2002 4 60 9 16 .0802253 |
5. | 23jul2002 5 79 13 23 .1012759 |
|------------------------------------------------------------|
6. | 22oct2002 6 119 19 34 .129815 |
7. | 22jan2003 7 163 28 49 .1694168 |
8. | 23apr2003 8 226 39 70 .2227229 |
9. | 23jul2003 9 291 54 97 .2903701 |
10. | 23oct2003 10 347 70 128 .3665293 |
|------------------------------------------------------------|
11. | 22jan2004 11 412 89 162 .4470252 |
12. | 22apr2004 12 471 110 200 .5280019 |
13. | 23jul2004 13 549 133 242 .6076685 |
14. | 22oct2004 14 616 157 288 .6828461 |
15. | 21jan2005 15 681 183 336 .7489257 |
|------------------------------------------------------------|
16. | 23apr2005 16 681 206 381 .7998888 |
17. | 23jul2005 17 681 226 418 .8352927 |
18. | 22oct2005 18 681 241 449 .8605611 |
19. | 21jan2006 19 681 254 475 .8791357 |
20. | 23apr2006 20 681 265 497 .8933169 |
|------------------------------------------------------------|
21. | 23jul2006 21 681 275 517 .9044613 |
+------------------------------------------------------------+

Examples of artpep command lines

. artpep, pts(25 30 40) edf0(0.5, 2) hr(1, 0.7)

. artpep, pts(25 30 40) datestart(15jan2008) epts(50) eperiods(3) edf0(0.5, 2) hr(1, 0.7)

. artpep, pts(5 7 12 18 25 30 40) eperiods(8) stoprecruit(12) edf0(0.5, 2) hr(1, 0.7)

. artpep using myres, pts(5 7 12 18 25 30 40) datestart(01nov1995) epts(45) eperiods(8) startperiod(3) stoprecruit(12) edf0(0.9 0.7 0.1, 1 2 9) hr(1, 0.7) replace

. use myres, replace

. line patients events date, sort

Authors

Abdel Babiker, MRC Clinical Trials Unit at UCL

Ab Babiker

Friederike Maria-Sophie Barthel, formerly MRC Clinical Trials Unit

Sophie Barthel

Babak Choodari-Oskooei, MRC Clinical Trials Unit at UCL

Babak Oskooei

Patrick Royston, MRC Clinical Trials Unit at UCL

Patrick Royston

Reference

Royston, P., and F. M.-S. Barthel. 2010. Projection of power and events in
clinical trials with a time-to-event outcome. Stata Journal 10: 386-394.

Also see

Online: help for artpepdlg, artsurv