survival analysis (Kaplan-Meyer)

[michtka]

Hi all, I got the next result from survival analysis (Kaplan-Meyer method) on time of failure of a treatment before complete week 9.

I have got the next result using PROC LIFETEST:

Here you are the part corresponding to the drug...placebo part is not important for my questions:

treatment  week censor survival number failed number left

drug           0             0           1         0               23

drug           3.0          0                      2               25        

drug           3.0          0           0.8        3              24   

drug          9.0           1           0.62     10             17 

drug          9.1           1          0.55       12             15

drug          9.2            1         0.53       11             14

And I want to create the final table:

week   survival failed number left treatment

3.0

6.0

9.0

I've got the next questions, I would like you to help me with:

1) Which value I need get to the final table for duration=3? The last one, that is populated?

2) Which value I need to get to the final table for durantion=6.0?...blank data, or I need to imputed it with the LOCF from the duration=3.0?

3) Which value I need to get to the final table for duration=9.0?...9.0, or can be possible 9.1 and 9.2 too?

I hope you can help me with this.

Thanks in advance.

V.

[Reeza · Accepted solution]

in proc lifetest, specify timelist=(3, 6, 9).

proc lifetest data=have timelist=(3,6,9);

There might be another option you can use as well to supress the list.

Also, the KM curve is stepped, so if you're missing a value you tend to take the lower or higher value depending on what you've specified.

[michtka]

Thanks Reza, for example, because KM curve is stepped, if I had to include week 4 that is not in the result, I would consider the survival value of week3?, because the function will be flat between [week3  and week9) with the value =0.8.

Is it right considerer Survival(Week4)=Survival(Week3)=0.8?

Thanks in advance.

V.

[michtka]

Yes, timelist opcion is doing it...thank you very much for your help Reeza.

[Reeza]

Just something to keep in mind, SAS will fill in the values appropriately

[SteveDenham]

SAS will fill in the values.  Sometimes it fills them in somewhat differently than you might want

Steve Denham