Code:
use https://www.pclambert.net/data/rott2b, clear
(Rotterdam breast cancer data (augmented with cause of death))
. // (Rotterdam breast cancer data (augmented with cause of death))
. range tt 0 5 101
(2,881 missing values generated)
. stset os, f(osi==1) scale(12) exit(time 60)
Survival-time data settings
Failure event: osi==1
Observed time interval: (0, os]
Exit on or before: time 60
Time for analysis: time/12
--------------------------------------------------------------------------
2,982 total observations
0 exclusions
--------------------------------------------------------------------------
2,982 observations remaining, representing
753 failures in single-record/single-failure data
13,038.968 total analysis time at risk and under observation
At risk from t = 0
Earliest observed entry t = 0
Last observed exit t = 5
. rcsgen age, gen(agercs) df(3) orthog
Variables agercs1 to agercs3 were created
. stpm2 agercs* recent chemo, ///
> tvc(agercs* recent chemo) dftvc(2) ///
> df(3) scale(hazard)
Iteration 0: Log likelihood = -2121.7864
Iteration 1: Log likelihood = -2109.6881
Iteration 2: Log likelihood = -2108.6861
Iteration 3: Log likelihood = -2108.6789
Iteration 4: Log likelihood = -2108.6789
Log likelihood = -2108.6789 Number of obs = 2,982
---------------------------------------------------------------------------------
| Coefficient Std. err. z P>|z| [95% conf. interval]
----------------+----------------------------------------------------------------
xb |
agercs1 | .2163973 .0403783 5.36 0.000 .1372573 .2955372
agercs2 | -.1843649 .0349476 -5.28 0.000 -.2528609 -.1158689
agercs3 | .0345448 .0355393 0.97 0.331 -.035111 .1042006
recent | -.2073141 .07534 -2.75 0.006 -.3549778 -.0596505
chemo | .2922621 .1073828 2.72 0.006 .0817956 .5027286
_rcs1 | .7684606 .0526326 14.60 0.000 .6653025 .8716186
_rcs2 | .1374124 .0412984 3.33 0.001 .056469 .2183557
_rcs3 | .0156698 .0093732 1.67 0.095 -.0027014 .0340409
_rcs_agercs11 | -.1162479 .0399127 -2.91 0.004 -.1944754 -.0380204
_rcs_agercs12 | -.0764194 .0298221 -2.56 0.010 -.1348697 -.0179691
_rcs_agercs21 | .000038 .033758 0.00 0.999 -.0661265 .0662026
_rcs_agercs22 | .0036754 .0255487 0.14 0.886 -.0463992 .0537499
_rcs_agercs31 | -.0043918 .0292079 -0.15 0.880 -.0616383 .0528546
_rcs_agercs32 | -.0137591 .0214704 -0.64 0.522 -.0558403 .0283221
_rcs_recent1 | .0855266 .0575237 1.49 0.137 -.0272177 .1982708
_rcs_recent2 | .0291833 .0418702 0.70 0.486 -.0528808 .1112475
_rcs_chemo1 | .0472015 .1116477 0.42 0.672 -.171624 .266027
_rcs_chemo2 | .060447 .0822471 0.73 0.462 -.1007544 .2216483
_cons | -1.500633 .0632174 -23.74 0.000 -1.624536 -1.376729
---------------------------------------------------------------------------------
.
. // Use "if" option to set the covariate distribution to that for patients
. // who got chemotherapy in the recent years.
.
. // 1) Predict for the patients who diagnosed in the recent years.
. standsurv if recent==1 & chemo==1, ///
> at1(recent 1 chemo 1) ///
> at2(recent 1 chemo 0) /// Prediction for patients who didn't get chemotherapy in the recent years
> contrast(difference) contrastvar(rs_diff_new) /// Calculate the difference between groups
> timevar(tt) ci atvar(wchemo_new wochemo_new)
.
. // 2) Predict for the patients who diagnosed in the past years.
. standsurv if recent==1 & chemo==1, ///
> at1(recent 0 chemo 1) ///　Prediction for patients who got chemotherapy in the past years
> at2(recent 0 chemo 0) /// Prediction for patients who didn't get chemotherapy in the past years
> contrast(difference) contrastvar(rs_diff_old) /// Calculate the difference between groups
> timevar(tt) ci atvar(wchemo_past wochemo_past)
.
. twoway line rs_diff_old rs_diff_new tt, sort
. list rs_diff_old* if tt==5
+-----------------------------------+
| rs_diff~d rs_~d_lci rs_~d_uci |
|-----------------------------------|
101. | .06619761 .01963877 .11275645 |
+-----------------------------------+
. list rs_diff_new* if tt==5
+----------------------------------+
| rs_dif~w rs_~w_lci rs_~w_uci |
|----------------------------------|
101. | .0583496 .01691349 .09978571 |
+----------------------------------+
.
end of do-file
