Dear list,

I am not familiar with survival analysis and I would need your help to
understand a result I have obtained.

I have used the following command line to look at number of events and
probability of survival at the first 5 years:
> su = summary(survfit(Surv(a[, Date], a[, Event]) ~ strata(a[,Prediction]),
data = a), times=c(0,1,2,3,4,5))

I have studied two kind of events (disease-free survival and metastasis free
survival), please see the results below.
At year 5, in group C2 I have one more patient with an event when looking at
DFS (13) than when looking at relapse (12). However, the probability is
higher when looking at DFS (0.23) than relapse (0.18), which I cannot
understand as I have one more event.

Can anyone explain or point to documentation explaining this? Is it due to
the fact that there was no more event between year 4 and 5 when looking at
DFS?

  Relapse
0 1 2 3 4 5
patients 40 34 32 24 15 9  C1 events 0 1 1 1 2 2
survival 1 0.97 0.97 0.97 0.92 0.92
patients 19 12 10 5 3 1  C2 events 0 6 8 10 11 12
survival 0.95 0.68 0.57 0.45 0.36 0.18















 DFS
0 1 2 3 4 5
patients 40 34 32 24 15 9  C1 events 0 1 1 1 2 2
survival 1 0.97 0.97 0.97 0.92 0.92
patients 19 12 9 4 2 1  C2 events 0 6 9 12 13 13
survival 0.95 0.68 0.51 0.31 0.23 0.23


Best wishes,
Audrey

-- 
Audrey Kauffmann
Bergonie Cancer Institute
229 Cours de l'Argonne
33076 Bordeaux
France
+33.5.56.33.04.53

	[[alternative HTML version deleted]]

