topic Re: Can you smooth a Kaplan-Meier curve in SAS? in New SAS User

Can you smooth a Kaplan-Meier curve in SAS?

TL93 — Tue, 11 Dec 2018 20:51:00 GMT

Hello everyone! How can I smooth my Kaplan-Meier curves in SAS?

Context: I am releasing results from a research center. According to their rules, every "step" in the Kaplan-Meier curve needs to have at least X number of respondents. Mine does not meet this requirement so I must smooth out the curve and eliminate the jagged "steps."

Here is my syntax for the Kaplan-Meier curves

proc lifetest data=cancer.modelone method=km plots=survival cs=none notable;
time duration*cancer(0);
strata sex;
symbol1 V=none color=blue line=1;
symbol2 v=none color=red line=1;
title1 font="Arial 11pt" Height=1 Bold 'KM Curve by Sex';
run;

Below is an illustration of what I want. I found these examples online but they are STATA outputs (STATA uses Lowess Smoothing ?? - I'm not familiar with STATA).

I am also not familiar with Macros or SQL. Thank you for your time!

Re: Can you smooth a Kaplan-Meier curve in SAS?

Reeza — Tue, 11 Dec 2018 20:53:57 GMT

You can get the output from the PROC LIFETEST and then apply a LOESS statement within SGPLOT to plot the data instead of using the default SAS output.

Re: Can you smooth a Kaplan-Meier curve in SAS?

TL93 — Tue, 11 Dec 2018 21:10:37 GMT

Can I apply LOESS to GPLOT?

I have used proc gplot because I wanted to adjust the x and y axis of the Kaplan-Meier figure. I got the output from PROC LIFETEST and used PROC GPLOT as shown:

proc lifetest data=cancer.modelone outsurv=kmgender noprint;
time duration*cancer(0);
strata sex;
symbol1 V=none color=blue line=1;
symbol2 v=none color=red line=2;
title1 font="Arial 11pt" Height=1 Bold 'KM Curve by Sex';
run;

goption reset=all ftext=simplex;
symbol1 line=1 color=blue i=stepj;
symbol2 line=1 color=red i=stepj;
axis1 label=(angle=90 'Survival Probability') order=(0.70 to 1 by .02);
axis2 label=('Time to Cancer Diagnosis (days)') order=(0 to 7875 by 1125);

proc gplot data=cancer.kmgender;
plot survival*duration=sex /vaxis=axis1 haxis=axis2;
title 'Kaplan-Meier Curve by Sex';
run;

What would the syntax look like with the LOESS statement?

Thank you!

Re: Can you smooth a Kaplan-Meier curve in SAS?

Reeza — Tue, 11 Dec 2018 21:21:48 GMT

I'm not familiar with GPLOT, but the LOESS examples are here:
https://documentation.sas.com/?docsetId=grstatproc&docsetTarget=p0e254y1nmv2fjn1t3jybtamodjp.htm&docsetVersion=9.4&locale=en#n164hcka7zsw9on1s2w0kb44tnf1